Table of Contents
Safety First: Electrical Safety 6
Service Panels 49
The Main Disconnect 49 Service Amperage 50 Inspecting Enclosures, Part 1 52 Inspecting Enclosures, Part II 54 Inspecting Enclosures, Part III 55 Fuse Panels 57 Breaker Panels and Breakers 59 Problem Panels 62 Quiz #4 64 3-Phase Panels 67 Phased Supply and Distribution 67 Panel Oddities 68 Quiz #5 69
Electrical Distribution 71
Wiring Types 71 Aluminum Wiring 73 Branch Circuit Connections 77 Protection of Wiring 80 120-Volt Terminations 83 Inspecting Receptacles 86 240-Volt Terminations 89 GFCI Circuits 90 GFCI Requirements 92 AFCI: Arc Fault Circuit Interrupter 94 Lighting Circuits 96 Quiz #6, Part 1 100 Quiz #6, Part 2 103
Basic Terms Simple Theory Conductor Sizes Quiz #1
7 11 13 18
Home Inspector Safety and Dangers 20
Electrical Portion of the House 20 The Basics 20 How an Electrical Circuit Works 20 How Injuries Occur 21 Standards of Practice 21 Warning Signs 21 What’s an Arc Flash? 22 How Serious Is an Arc Flash? 22 Precautions for Inspectors 23
Service Entrance 24
Service Terminology 24 Service Drop 24 Service Mast and Attachments 28 Service Lateral 31 Electrical Meters and Bases 32 Service Entrance Cable 33 Quiz #2 36
Grounding and Bonding 39
Grounding Systems 39 Bonding of Components 43 Panels and Enclosures 44 Quiz #3 47
Appendix I: Answer Keys 106
Answer Key for Quiz #1 106 Answer Key for Quiz #2 106 Answer Key for Quiz #3 107 Answer Key for Quiz #4 107 Answer Key for Quiz #5 108 Answer Key for Quiz #6, Part 1 108 Answer Key for Quiz #6, Part 2 109
How to Perform Residential Electrical Inspections 6 Introduction
Safety First: Electrical Safety Electricity Kills
The primary responsibility for a home inspector, when evaluating electrical systems in the home, is the safety of himself and his clients, both at the time of inspection and after they move into the property.
This is also one of the few areas that most home inspectors would cite as “deficient”—systems that were acceptable when the home was built, but would now be considered sub-standard. A lack of GFCIs, for example, would fall into this category.
The home inspector should be especially cautious when evaluating the service panels. An electrical system and distribution panel can kill an inspector. According to InterNACHI’s Home Inspection Standards of Practice, a home inspector is not required to do anything that he thinks is unsafe, including removing covers from electrical boxes or panels and exposing electrified, “live,” or “hot” electrical components within.
Be sure to refer to InterNACHI’s Standards of Practice to read the requirements and exclusions for conducting the electrical portion of a residential property inspection.
A home inspector is not required to remove the dead front (the front cover) of any electrical panel or box. Removing it is hazardous. InterNACHI® does not require or recommend home inspectors to remove the dead front.
Inspectors should follow these basic safety rules when inspecting live electrical components:
- Use protective eyewear.
- Wear electrician’s gloves (600-volt rated).
- Do NOT wear nylon or polyester clothing.
- Do NOT allow the client to get between yourself and any live components.
- Visually inspect the panel before removing the dead front.
- Do NOT open a panel that is either very rusted or shows signs of moisture.
- Do NOT open any panel that is buzzing or arcing.
- Before removing the dead front, test for stray voltage with the back of your hand, or use a voltage tic.
- Do NOT insert any probes or tools into the service panel. • NEVER put ladders up under the service drop. If in any doubt about anyone’s safety, defer the inspection to a licensed electrical contractor.
hot or live wire panel earth ground ground rod main panel panel cover outlet
grounding electrode conductor
service or distribution electrical panelboard with a service disconnect dead front
lighting and/or receptacle outlet
Using the Correct Terminology
One of the challenges facing home inspectors doing the electrical portion of home inspections
is getting the terminology right. Many home inspectors end up looking inexperienced or unprofessional by not knowing the correct verbiage. For example, a wire is more properly called a conductor.
Here is a list of commonly used terms and their correct usage. Understanding these terms will help the inspector recognize improper panel wiring, especially in the case of grounded and ungrounded conductors.
|Common Terminology||More Formal Terminology or Description|
|neutral wire||grounded conductor|
|earth or ground wire||equipment grounding conductor|
|main (disconnect)||service disconnect|
|sub-panel||distribution panelboard without a service disconnect|
|wires to outlets||branch circuit conductors|
|service to remote panel||feeder|
Ampacity refers to the maximum current in amps that a conductor can carry without exceeding its maximum temperature rating.
An appliance is tilization equipment that performs a function. such as clothes washing or air conditioning.
How to Perform Residential Electrical Inspections 8
An arc-fault circuit interrupter (AFCI) is a device that provides protection from the eects of arc faults by recognizing arcing, and de-energizing the circuit when an arc fault is detected.
American wire gauge (AWG) is a standardized wire gauge system used since 1857 predominantly in North America for the diameters of round, solid, nonferrous, electrically conducting wire. The cross-sectional area of each gauge is an important factor for determining its current-carrying capacity. Increasing gauge numbers denote decreasing wire diameters.
AWG tables are for a single, solid, round conductor. The AWG of a stranded wire is determined by the cross-sectional area of the equivalent solid conductor. Because there are also small gaps between the strands, a stranded wire will always have a slightly larger overall diameter than a solid wire with the same AWG.
To be bonded is to be connected in order to establish electrical continuity and conductivity.
A branch circuit is the conductor between the !nal over-current device protecting the circuit and the outlet(s).
A cabinet is a mounted enclosure with a swinging door.
A circuit breaker is a device designed to open and close a circuit by non-automatic means and to open the circuit automatically when there’s an over-current.
Current is the measurement of the rate of $ow of electricity through a conductor. Current is measured in amps.
A dead front is without live parts that are exposed to someone on the operating side of the equipment.
A device is a unit of an electrical system, other than a conductor, that is intended to carry or control but not utilize electricity. Examples of devices are switches and thermostats.
This is a device by which the conductors of a circuit can be disconnected from their source of supply.
The feeder is a circuit of conductors between the service equipment and the !nal overcurrent device. Circuits feeding subpanels are called feeders. The conductors between two overcurrent devices are called feeder conductors.
In North America, conductors larger than 4/0 AWG are generally identi!ed by the area in thousands of circular mils (kcmil), where 1 kcmil = 0.5067 mm%. The next wire size larger than 4/0 has a cross section of 250 kcmil.
A ground-fault circuit-interrupter (GFCI) is a device that protects a person by de-energizing a circuit when a current to ground exceeds the value for the device.
Line refers to the incoming power. The line side of the equipment will be where the source of the power is terminated.
Load refers to the outgoing power.
An outlet is a point on the wiring system where current is taken to supply equipment. Examples of an outlet include receptacles, light !xtures, smoke detectors and appliances. A switch would not be an outlet because no current is taken at a switch; current simply passes through a switch.
Overcurrent Protection Device
An overcurrent protection device is set to open a circuit when the current exceeds a set value. Overcurrent protection devices are usually circuit breakers and fuses.
A panelboard is a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the controlling of light, heat or power circuits, and is mounted in a cabinet, and is accessible only from the front.
A receptacle is a contact device installed at the outlet for the connection of an attachment plug.
This is an outlet where one or more receptacles are installed.
How to Perform Residential Electrical Inspections 10
Romex® is the trade name for a type of NM cable. Romex® is the most commonly used wiring in homes. The proper name for this cable is nonmetallic sheathed cable. A 14/2 with ground would contain three 14-gauge conductors: one black insulated conductor (the hot); one white insulated conductor (the neutral); and one bare conductor (the ground wire).
The service is de!ned as the conductors and equipment used for delivering energy from the service utility to the wiring system of the home.
SE and SEU Cable
The “SE” in SE cable stands for service entrance cable, which is not commonly used for service cable any longer, but is used for branch circuit and feeder wiring in homes. SEU is an SE cable, with the U indicating “underground.” SEU cable is identi!ed for underground use. It has a moisture- resistant covering. SEU cable usually contains three conductors, two of which are insulated, and one a bare equipment grounding conductor. SE cables are jacketed with gray, sunlight-resistant polyvinyl chloride.
Nomenclature and Abbreviations
There are alternate terms used in the electrical industry to specify AWG wire sizes. 4 AWG (proper) could also be written as:
• #4 (the number sign is used as an abbreviation for “number”) • No. 4 (“No.” is the abbreviation for “number”)
• No. 4 AWG
• 4 ga. (the abbreviation for “gauge”)
000 AWG (proper for large sizes) could also be written as:
• 3/0 (common for large sizes), which is pronounced “3 aught” • 3/0 AWG
Common wires used electric power distribution in homes can be identi!ed by a wire size followed by the number of wires used in the cable assembly. The most common types of distribution cable, NM-B, is generally written in the following three ways:
- #14/2 (also written “14-2”). This is a nonmetallic sheathed bundle of two solid 14 AWG wires. The insulation surrounding the two conductors is white and black. This sheath for 14 AWG cable is usually white when used for NM-B wiring intended for electrical distribution in a dry location. Newly manufactured cables without a separate ground wire (such as #14/2) are obsolete.
- #12/2 with ground (also written “12-2 w/gnd”). This is a nonmetallic sheathed bundle of three solid 12 AWG wires having a bare ground in the middle of two insulated conductors in a $at- shaped NM-B yellow-colored sheath. The color is a North American industry standard for cables made since 2003, and aids identi!cation.
• #10/3 with ground (also written “10-3 w/gnd”). This is a nonmetallic sheathed bundle of four solid 10 AWG wires having a bare ground and three insulated conductors twisted into a round- shaped NM-B orange-colored sheath. The insulated conductors are black, white, and red. Some cable of this type may be $at to save copper.
AWG is colloquially referred to as gauge and the zeroes in large wire sizes are referred to as aught. Wire sized 1 AWG is referred to as “one gauge” or “No. 1” wire. Similarly, smaller diameters are pronounced “x gauge” or “No. X” wire, where x is the positive integer AWG number. Consecutive AWG wire sizes larger than No. 1 wire are designated by the number of zeroes:
• No. 0, typically written 1/0 and is referred to as “one aught” wire;
• No. 00, typically written 2/0 and is referred to as “two aught” wire; and • No. 000, typically written 3/0 and is referred to as “three aught” wire.
Know What You’re Talking About
Getting the terminology right will avoid a lot of “Your inspector doesn’t know what he’s talking about” comments from local electrical contractors.
Understanding How Electricity Works
Electrical current is actually the movement of electrons $owing along a conductor in much the same way as water $ows through a pipe. The same fundamental principles apply in the same way: the bigger the pipe, the more $ow it can handle. Conversely, smaller pipes can handle small supplies. This is the principle behind resistance.
An analogy to understanding electricity is a water pipe, where the voltage is the water pressure, the current is the $ow rate, and the resistance is the size of the pipe. Current ($ow rate or amps) is equal to the voltage (water pressure or volts) divided by the resistance (size of the pipe or ohms).
Amps = E / R
Current = $ow rate = amps = I Voltage = pressure = volts = E Resistance = pipe size = ohms = R
Let’s see how this relation applies to the plumbing system. Assume you have pressurized water coming out of a garden hose. When you increase pressure, more water comes out of the hose. Similarly, in an electrical system, when you increase the voltage (pressure, volts, or E), the current ($ow rate, amps, or I) increases.
Now, assume you increase the diameter size of the garden hose. More water will come out of the hose. Similarly, when you decrease the resistance in an electrical system, the current $ow increases.
How to Perform Residential Electrical Inspections 12
Electrical power is measured in watts. In an electrical system, power or watts (W) is equal to the voltage (V) multiplied by the current (I).
To understand power, think of taking that water pipe and pointing it at the top of an old waterwheel. To increase the power generated by the waterwheel, you can: (a) increase the pressure of the water coming out of the pipe, or (b) increase the $ow rate of the water.
Measuring Electrical Forces
When discussing electrical supply, we use many dierent terms to quantify the amount of available power, the amount of work it can do, the resistance of the components, and, therefore, its safe operating parameters. Here are some easy-to-understand de!nitions and explanations of the terminology.
Resistance limits the conductor’s ability to allow the $ow of electrons, just as friction causes losses in any pipe or ductwork. This is expressed in Ohms.
Electromotive force is what drives electrons along the conductor, and is expressed as voltage or volts. Current is the $ow of electrons driven by electromotive force through a given resistance. This is
expressed as amps.
Power is the amount of work that the electrical $ow can do. This is expressed as watts or kilowatts (1,000 watts).
Georg Simon Ohm was a German physicist born in Erlangen, Bavaria on March 16, 1787. Ohm started his research with the then-recently invented electric cell (invented by Italian Conte Alessandro Volta). Using equipment of his own creation, Ohm determined that the current that $ows through a wire is proportional to its cross-sectional area, and inversely proportional to its length. Using the results of his experiments, Ohm was able to de!ne the fundamental relationship between voltage, current and resistance.
These fundamental relationships are of such great importance that they represent the true beginning of electrical circuit analysis.
Unfortunately, when Ohm published his !ndings
in 1827, his ideas were dismissed by his colleagues. Ohm was forced to resign from his high school teaching position, and he lived in poverty. However,
his research eorts gained a lot of support outside of Germany. In 1849, Georg Simon Ohm was !nally recognized for his eorts by being appointed as a professor at the University of Munich.
How Do Ohm’s Laws Help Us?
Ohm’s Laws are basically a series of mathematical models that show us how to determine safe working loads for conductors and electrical components. This allows us to understand why, for
Introduction 13 example, a 30-amp fuse should not be connected to a 14-awg wire (having to do with resistance and
Ohm’s Laws de!ne the relationship between voltage, current and resistance, where I is the current, measured in amperes (amps/A), R is the resistance, measured in Ohms (&), E is the electrical potential (voltage), and W is power, measured in watts.
Common Ohm’s Laws Are:
Watts equals volts times amps, or W = E x I.
Another equation would be: amps = watts divided by volts, or I = W / E.
AMPS MEASURE CURRENT: The volume of the current (the number of electrons $owing past a given point per second) is measured in amperes, or amps.
VOLTS MEASURE PRESSURE: The pressure under which electricity moves is measured in volts. Electricity arrives at household circuits at a “pressure” of 120 or 240 volts.
WATTS MEASURE POWER: Power is measured in watts, and you can compute wattage by multiplying amperage and volts.
Assume that a standard incandescent light bulb is drawing 1/2-amp from a 120-volt circuit using 60 watts of power (120 volts x 0.5 amps = 60 watts). To calculate amps, divide watts by volts.
Assume an electric clothes dryer is using 240 volts and is rated at 7,200 watts, and pulls 30 amps (7,200 / 240 = 30). This means that the dryer must be protected by a 30-amp circuit breaker, and the wire-carrying current to it must be No. 10 copper, which is rated for 30 amps.
How much does it cost to operate a portable electric heater? The wattage for an electric heater is usually found on a label on the unit. Assume that it is 1,000 watts. Assume that the heater is used an average of 45 hours during the winter months (half-hour per day for the three winter months), and the utility’s electric rate during the winter is $0.068. Then, 1,000 watts/1,000 = 1 kW x 45 hours of operation = 45 kWh x $0.068 = $3.06.
Now, let’s assume that we have an 8-amp heater. The calculation changes just a bit to 8 amps x 120 volts of household current = 960 watts/1,000 = 0.96 kW x 45 hours = 43.2 kWh x $0.068 = $2.94.
Understanding the Limitations of Conductors
As we saw with Ohm’s Laws, resistance is key to a conductor’s ability to safely deliver the amount of power that a circuit needs. Think back to the pipe: the bigger the pipe, the lower the resistance.
When evaluating the electrical supply, we need to recognize that copper and aluminum conductors are not the same. Although they are both commonly used in a residential supply, copper inherently has less resistance to the $ow of electrons than aluminum does.
How to Perform Residential Electrical Inspections 14 For this reason, aluminum conductors are always one to two sizes larger than the equivalent copper
one for any given amperage.
Jumping ahead a bit, single-strand aluminum branch circuit wiring should always be fully evaluated by a licensed electrical contractor. (Multi-strand aluminum wires, as seen on service entrances and high-amperage circuits, are not a problem.) This issue is studied at greater length later in the text.
As we have seen, for larger amperages, we need larger conductors. The following table is a general guide to sizing conductors for feeders and services.
|Sizing Conductors for Feeders and Services (refer to the National Electrical Code®)|
|Service or Feeder Rating (in amps)||Conductor (AWG or kcmil)|
|Aluminum or Copper-Clad Aluminum||Copper|
|NEC® 215.2, 230.23, 230.31||Service and feeder conductors must be sized according to the calculated load.|
|NEC® 310.15||Service and feeder conductors for single-phase, 120/240-volt electrical systems may be sized using Table 310.15(B)(7).|
|Sizing Conductors for Feeders and Services (refer to the National Electrical Code®)|
|Service or Feeder Rating (in amps)||Conductor (AWG or kcmil)|
|Aluminum or Copper-Clad Aluminum||Copper|
|NEC® 310.15||Table 310.15(B)(7) may only be used for dwelling-unit services or feeders if the service or feeder supplies all loads associated with the dwelling unit. The table may not be used for sizing conductors supplying power to panelboards, such as HVAC disconnects, or subpanels supplying only a portion of the load.|
How to Perform Residential Electrical Inspections 16 The following table is a general guide to sizing standard overcurrent devices and their related cables.
|Circuit Size (in amps)||Copper NM Cable||Copper SE Cable||Aluminum SE Cable|
|Sizes of Standard Overcurrent Device (Breaker or Fuse)||15||#14||–||–|
|Table is sourced from NEC® 240.4, 240.6, Table 310.15, 334.80, and 338.10.|
|Overcurrent Protection Rating|
|Size AWG||Max breaker rating||Size AWG||Max breaker rating|
|14-gauge||15 amps||12-gauge||15 amps|
|12-gauge||20 amps||10-gauge||25 amps|
|10-gauge||30 amps||8-gauge||30 amps|
AWG stands for American Wire Gauge, which is a standardized wire gauge system.
Key Point: The maximum breaker rating must not exceed the allowable ampacity of the conductor.
The smaller conductor sizes are normally single-strand conductors, but as they get bigger, they switch to multi-strand so they can be easily worked. It is unusual to see a conductor of less than 8
AWG to have multiple strands.
Again, we’ll come back to it later, but remember to look for single-strand (solid) aluminum branch circuit wiring, especially in homes built between the mid-1960s and the mid-1970s. The presence of solid aluminum branch circuit wiring in a home is a major defect. If you observe indications of such wiring type and deem it a defect, report it.
How to Perform Residential Electrical Inspections 18
1. Which of the following should not be worn during an inspection?
safety glasses leather shoes nylon clothing
2. The following item is safe to insert into an electrical panel:
none of these a torque wrench an amp probe a wire gauge
3. The electrical panel should not be opened if the following conditions exist: ____________.
any of these
moisture dripping from the enclosure rusted enclosure
sounds of arcing
4. The correct name for a live wire is ___________.
a grounded conductor
an ungrounded conductor a grounding conductor
5. An electrical panel cover is more properly called the __________.
6. A service panel that does not contain the disconnect is called the __________.
7. Wires to outlets are called __________.
branch circuit conductors
8. Electromotive force is measured in ___________.
watts amps volts ohms
9. Ohms are a measurement of __________.
10. Voltage is equal to ____________.
power x amperage watts x current
amps x resistance
11. Finish the equation: W = E x ___
O Q I R
12. Aluminum branch circuit conductors should be sized ________ copper.
two sizes smaller than
the same as
one to two sizes smaller than one to two sizes larger than
13. A 20-amp breaker should feed a minimum ______ conductor.
12-AWG 8-AWG 14-AWG 10-AWG
14. What would be the minimum service entrance cable size for a 200-amp supply?
1/0 copper or 2/0 aluminum 2/0 copper or 4/0 aluminum 2/0 copper or 1/0 aluminum 4/0 copper or 2/0 aluminum
Answer Key is on page 106.
How to Perform Residential Electrical Inspections 20 Home Inspector Safety and Dangers
Electrical Portion of the House
Home inspection is one largely unregulated industry whose professionals must nevertheless be aware of their safety and that of their clients at all times. Part of this awareness is being mindful
of one’s surroundings, which can be challenging because the “workplace” changes with every appointment. Aside from inspecting a roof from an area above the ground, the electrical portion of a home inspection is arguably the most dangerous. Many things can go wrong in an instant, and some mishaps can be fatal. That’s why, even as generalists, home inspectors should understand what causes electrical shocks and arc $ashes so that they can avoid them.
The typical electrical service for homes in North America is a 120/240V split-phase system provided by a pole-mounted distribution transformer located at the service drop, which is made up of two 120-volt lines and a neutral line. This triplex cable may include a messenger cable located in the middle of the neutral conductor that provides support over long spans. The neutral line from the pole is connected to an earth ground near the service panel, which is usually a conductive rod driven into the earth. The service drop provides the home with two 120-volt lines of opposite phase, so 240 volts can be obtained by connecting a load between the two 120-volt conductors, while 120- volt loads are connected between either of the two 120-volt lines and the neutral line. The 240-volt circuit is used for a home’s electrical appliances that require substantial power, such as a furnace, water heater, air conditioner, washer and dryer, and oven/range. The 120-volt circuit is used for lighter electrical loads, such as household lighting, and portable appliances and electronics that are plugged into the home’s standard two- or three-prong (with a grounding wire) electrical receptacles or outlets.
Homes in European countries use three-phase power having longer service drops that can serve multiple residences, which is an economical approach to providing power to dense populations in small areas. This type of service drop consists of three phase wires and one grounded neutral wire.
How an Electrical Circuit Works
Everyone should understand that it’s possible to receive an electrical shock whenever electrical power is present, regardless of the level of power or the presence of any protective devices.
An electrical circuit requires a minimum of two wires through which electric current (in the form of electrons) $ows. Current is measured in amperes (amps, for short), which travels from a power source (such as the local utility), through the device it operates, called the load, and then back to the source to complete the circuit. In AC or alternating-current wiring, there are about 120 volts in the
“hot” or energized wire. This voltage provides the momentum that forces the electrons to $ow in the circuit.
The power switches on electrical devices are wired on the hot or “live” side of the circuit. The return conductor, known as the neutral, is at 0 volts because it is grounded at the electrical panel. Most 120-volt circuits are wired to deliver 15 or 20 amps of current.
Home Inspector Safety and Dangers 21
How Injuries Occur
Modern electrical systems are wired with circuit breakers, or with fuses in older construction. These devices serve as over-current protection and are rated in amps. Most household circuits are wired for 15 or 20 amps. Over-current protection devices are designed to protect the electrical system’s wiring and equipment from overheating, but they may not protect a person from electrical shock, which is why any type of component in the system should be approached with caution.
By coming into contact with a live load or energized wire, a person’s body (even a !nger) can complete a circuit by connecting the power source with the ground. If this happens, it’s likely that the person will sustain an injury. Most fatal injuries result from high-voltage exposure, but it’s possible to incur a severe injury from low-voltage power if it has a high-current $ow. Even if the current isn’t high, a person could be shocked or even electrocuted without ever tripping a circuit breaker or blowing a fuse. Currents of 50 to 100 milliamperes (1 mA = 1/1,000 of 1 amp) can be fatal.
Standards of Practice
According to InterNACHI’s Home Inspection Standards of Practice, the inspector is not required to:
- measure or determine the amperage or voltage of the main service equipment;
- remove panelboard cabinet covers or dead fronts;
- insert any tool, probe or device into the main panelboard, sub-panels, distribution panelboards, or electrical !xtures; or
- operate any electrical disconnect or over-current protection devices. However, some inspectors may choose to go beyond the Standards of Practice because they suspect some sort of defect and want to provide fuller information in their reports for their clients. Warning Signs Nevertheless, there are warning signs that a panel, box, or the system in general may be compromised, and these should persuade the inspector to defer further evaluation to a licensed electrical contractor:
- scorch marks on the dead front or the panelboard door, indicating a past or recent arc $ash;
- rust, which indicates past or recent moisture intrusion;
- missing or open breakers that cannot be con!rmed to be de-energized;
- overloading of the circuits with DIY wiring;
- uninsulated wiring;
- excessive dust, dirt and debris inside the panelboard; and/or
- any signs of water inside, around or below the panelboard, which can lead to shock or electrocution.
How to Perform Residential Electrical Inspections 22 What’s an Arc Flash?
An arc $ash occurs when a $ashover of electric current leaves its intended path and travels through the air from one conductor to another, or to neutral or ground. It often happens unexpectedly and can be explosive but brief, or it can last seconds and be rather visually spectacular. It can cause a little damage or it can disable a system and require the replacement of equipment. An arc $ash of any size is quite dangerous because its path is unpredictable; it will be attracted to the nearest item with the greatest conductivity, such as an unsuspecting rodent or house pet, or a person. An arc $ash can cause a serious electrical burn or even fatal electrocution.
An arc $ash can have various catalysts, including:
• excess dust;
• component failure;
• faulty system installation;
• dropping a metal tool, which may cause even a small spark; and/or • accidental contact.
How Serious Is an Arc Flash?
There are three factors that will determine the severity of an injury caused by an arc $ash:
• temperature; and
• the time it takes for the circuit to break.
An injury due to an arc $ash can be quite serious because of the violent nature of such a powerful burst of electrical energy. The light from an arc $ash can be blinding and disorienting. The heat caused by an arc $ash can be as high as 35,000° F, causing serious contact burns, as well as risk of catching !re. It can create a blast pressure of up to 2,000 pounds per square foot, sending damaged and super-heated electrical components $ying through the air like shrapnel, with a sound blast as loud as a gun !ring (140 decibels). Combine all these unexpected jolts of sensory overload and the physical consequences can be impossible to avoid.
In addition to the inspector being blinded (temporarily or permanently) and/or severely burned, another result of an arc $ash is that it can set electrical components on !re, and the proximity of the inspector means that s/he’ll likely inhale toxic vapors, which can cause respiratory and neurological damage, depending on the duration of exposure. Also, the force of the shockwave can rupture eardrums. Furthermore, being shocked by a current above 75 mA can cause the inspector’s heart
to go into a state of ventricular !brillation, which causes it to beat irregularly and rapidly without pumping any blood. If this condition doesn’t quickly normalize, either by itself, using CPR, or with the aid of a de!brillator, it may lead to a heart attack, which can be fatal. If the brain is deprived of oxygen for more than three minutes as a result, this, too, can be fatal, or it can land the inspector in a vegetative state.
It’s not uncommon for an inspector to never fully recover his previous quality of life after experiencing an injury from an arc $ash.
Home Inspector Safety and Dangers 23 Precautions for Inspectors
1. Assess your risk tolerance. You are not required to perform an invasive electrical inspection. Removing the dead front of the electrical panelboard exceeds InterNACHI’s Standards of Practice. Event if a home inspector is highly con!dent of their technical training, as well as the situation, and he or she can also con!rm that the system is de-energized, any suspected problems that require an invasive inspection should be disclaimed and deferred to a licensed electrical contractor.
2. Wear PPE. Regardless of whether you choose to exceed the Standards of Practice, always have available and wear the appropriate PPE, including !re-resistant clothing and insulated gloves made speci!cally for working with electrical equipment. It’s also wise to use protective eyewear. Even a small spark can cause a severe eye injury.
3. Check your surroundings. If there is a lack of ground-fault circuit interrupters (GFCIs), or if there is evidence of a water leak or moisture intrusion, or if the panelboard or electric box has scorch marks, potentially indicating a previous arc $ash or electrical !re, pay attention to these and other clues, as they may lead you to immediately defer the electrical portion of your home inspection. Again, assess the risk and then decide whether to proceed.
4. Use the appropriate tools. According InterNACHI’s Standards of Practice, inspectors are required to:
…test all ground-fault circuit interrupter receptacles and circuit breakers observed and deemed to be GFCIs using a GFCI tester, where possible…
Make sure your tester is working properly before your inspection appointment. An infrared camera is also a tool for helping to detect hot spots during the electrical inspection.
5. Protect your clients. Many inspectors encourage their clients to accompany them during the inspection so that they can point out important shuto valves and switches, and discuss maintenance items. However, inspectors should use extreme caution when deciding whether to have the client with them during inspection of the panelboard if signs indicate that it may not be safe. This is true for any area of the home that exhibits signs of instability or some apparent hazard. Using the InterNACHI® “Stay Back” Stop Sign (available from Inspector Outlet) can help keep clients, their family members and
their realtors away from an inspected area. It’s also useful for limiting the inspector’s liability if the client chooses to ignore your warnings and suers an injury during the inspection.
Arc $ashes are just one of the more serious examples of what can go wrong during an inspection, which is why inspectors should follow their training, as well as their instincts, and protect themselves and their clients on the job. It’s always better to be safe than sorry and incur a grievous injury, which can put both your livelihood and life at risk.
How to Perform Residential Electrical Inspections 24 Service Entrance
The service-entrance conductors are the service conductors located between the terminals of the service equipment (main disconnect) and a point usually outside the building, clear of building walls, where they are joined by a tap or splice to the service drop or overhead service conductors.
The service point is the point of connection between the facilities of the service utility and the premises’ wiring.
The overhead service conductors are also the overhead conductors between the service point and the !rst point of connection to the service-entrance conductors at the structure.
The service equipment is the necessary equipment, usually
consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load-end of service conductors at a building or designated area,
and intended to constitute the main control and cuto of the supply.
It is understood that raceways, !ttings and enclosures housing service conductors are also part of the service equipment. Meter socket enclosures are not considered service equipment. Meter enclosures do not have interrupting ratings, disconnecting means, or over-current protection.
Service Entrance 25 The service drop is the overhead service conductors located between the utility electric supply
system and the service point.
The service point is the point of connection between the facilities of the service utility and the wiring at the house.
In many older residential areas, and practically all rural locations, the electrical supply is delivered to the property via overhead conductors strung on wooden utility poles. The high-voltage lines connect directly to the property through a transformer delivering mains power.
While the service overhead belongs to the utility company, the inspector should still evaluate it, particularly to indicate the available voltage, its clearances, and any mechanical damage.
The Cable Assembly
Most residential buildings are supplied with 120/240-volt services. This means that the cable assembly is made up of two ungrounded (live or hot) conductors, each supplying 120 volts, and one neutral or grounded conductor acting as the return.
Many homeowners mistakenly believe that the three conductors are one each of a live, a neutral, and a ground. In fact, to have 240 volts available in the home, we need two separately derived 120-volt ungrounded conductors, and a grounded conductor. The ground does not return to the pole through the cable assembly; the grounded conductor serves the role of the return path to the transformer.
There are, however, a few variations on the theme.
It is not unusual to see one of the live conductors tied back. This is indicative of a 120-volt-only supply, which is still found at some older properties, and apartments and condos.
Conversely, the inspector may see cable assemblies with more than three connected conductors. This is typically a 3-phase supply commonly found in both commercial and agricultural environments.
In the case of 120-volt-only supply, we recommend that the inspector’s report shows this limitation.
In the case of high-voltage, 3-phase supplies, we recommend that the inspector defers this part of the electrical inspection to a quali!ed industrial or commercial electrical contractor.
How to Perform Residential Electrical Inspections 26 Service Cable Connections
The service cables are connected to the service entrance cables by crimped connectors, which are then covered in an insulated sleeve.
The image at right shows that the insulation material on two of the connections is missing, and the third is damaged.
Attachment to the Structure
As already discussed, the neutral (grounded
conductor) also serves as the main physical connection (though insulated) to the building. The inspector should ensure that this strain relief is not detached or pulling away from the structure.
At some older properties, the conductors are not in an assembly, and each has its own connection to the structure, but this is rare these days, and probably in need of replacement.
The point of attachment of the service-drop conductors to a building or structure must have a clearance above the !nished grade of at least 10 feet.
As can been seen in the table below, the overhead service must have some minimum separation from both the structure itself and any walkways, driveways, balconies, patios and swimming pools.
Very often, an inspector will see properties that have been modi!ed, and the service overhead should have been relocated, but wasn’t.
This can obviously lead to some dangerous conditions,
especially over swimming pools and decks where the service connections could be accidentally reached by the homeowner.
|Vertical Clearance from Grade for Open Overhead Service Conductors|
|Location||Minimum Clearance Requirement|
|over public streets, roads, alleys, and parking areas with truck trac||18 feet|
|over commercial parking areas||18 feet|
|over swimming pools||22 feet, 6 inches above, and 10 feet horizontally|
Service Entrance 27
|Vertical Clearance from Grade for Open Overhead Service Conductors|
|Location||Minimum Clearance Requirement|
|over residential properties, yards, driveways, and any other parking areas||12 feet|
|over all walking areas, sidewalks, decks, roof surfaces, and patios used by pedestrians only measured from !nal grade or other accessible surfaces areas||10 feet at the electrical service entrance|
|above roof surfaces having a slope of less than 4:12 and not subject to pedestrian trac||8 feet maintained for a distance of at least 3 feet in all directions for the edge of the roof|
|over roof surfaces having a slope of 4:12 or greater||3 feet|
|over roof surfaces where voltage is 300 or less and the roof area is guarded or isolated||3 feet|
|termination of through-the-roof raceway or approved support above the overhanging portion of the roof that is less than 4 feet measured horizontally||18 inches|
|from the sides of doors, porches, decks, stairs, ladders, !re escapes and balconies, and from the sides and bottom of windows that open||3 feet from the bottom, sides and front|
How to Perform Residential Electrical Inspections 28
Another common clearance problem is caused by trees and shrubs interfering with the overhead supply. The inspector should take the time to eyeball the length of the supply from the pole to the attachment point on the structure, and report
on any tree limbs touching the conductors.
Also remember that the branches are heavier during the summer and weigh down further on the conductors. What may be marginal during the winter months may well cause a problem later in the growing season.
The inspector should recommend that any limbs within 5 to 6 feet of the cable assembly be cut back.
Service Mast and Attachments
In most cases where the home is fed by a service overhead, the supply is fed down the outside of the house through a conduit known as the service mast. In some cases, the cable assembly is of type SE, which requires no conduit.
Service Entrance 29
The masthead (or gooseneck, as it is sometimes called when SE cable is used) is at the top of the mast itself. Its purpose is twofold: !rst, it acts as a rain cap to stop moisture from entering the conduit; and, second, it provides the bushings to prevent the individual conductors from being damaged by rubbing against the metal components.
The masthead should be undamaged and securely fastened to the service mast.
The inspector should report any loose !ttings or cracks in the masthead and its clamp.
Before the conductors enter the service masthead, there should be a loop in the conductors. The lowest point of these loops should be 12 inches below the point of entry into the masthead itself. This is to prevent rainwater from migrating along the conductors or cable assembly and pouring down into the masthead.
Type SE Cable
How to Perform Residential Electrical Inspections 30
Service masts for supporting the service drop and overhead service conductors should be of adequate strength or be supported by braces or guy wires. A mast in excess of 3 feet above a roof surface may require support. The weight of the cable assembly is considerable and, when applied to an overly tall mast, has the ability to bend it right over.
For the same reason, the inspector should report anything other than the cable assembly being supported by the service mast.
It is all too common to see telephone cables, TV cables, satellite dishes, clotheslines, and supplies to remote buildings being supported by the service mast.
The inspector should report all of these as in need of repair or relocation.
Service Mast Flashings
As with any other projection through the roof surface, the service mast should be adequately $ashed to prevent water from entering the building.
It is not unusual to see signs of water leakage through the roof due to poor mast $ashings. Because the mast is generally outside of the conditioned space, these leaks commonly go on for years, causing considerable damage to the roof sheathing and fascia.
Service Mast Attachment
In the case of rigid conduit service masts, they should be attached to the structure every 5 to 6 feet throughout their length, and should also have a clamp within 12 inches of either side of the meter base, as well as at the top of the mast, if it doesn’t project through the roof.
It is all too common to see the attachment clamps not replaced or loose after the building siding has been replaced.
Any defects in this area should be reported as in need of repair by a licensed electrical contractor.
The “SE” in SE cable stands for service entrance. This cable assembly is designed with a high degree of resistance to mechanical damage and the sun’s UV (ultraviolet) rays. For this reason, it is not installed in a conduit, but is attached directly to the building.
However, if it is located some place where it is likely to be subject to physical damage from car doors, etc., then it must be protected by a conduit.
Service Entrance 31
It should still feature a gooseneck or service-head cap, and the end where the individual conductors exit the sheathing should be protected from moisture intrusion by a heat-shrunk sock if a gooseneck is used. This type of cable should be attached to the building every 30 inches along its length, and within a foot of its top and any meter can.
Underground Service Supply
As previously discussed, in most newer and densely populated areas, the electrical supply is fed underground. This is properly called a service lateral.
Other than during the very early stages of construction, the home inspector is not able to evaluate the conduit or cable, but, for informational purposes, there are some restrictions that apply to underground services that should be noted.
Type UF cable is rated for direct burial and has an outer sheathing that is resistant to moisture and damage from soil. This type of cable must be buried to a depth of 18 to 24 inches (depending on the location, as described in section/table 300.5 of the NEC®) and, if embedded in rocky ground, it must be installed in a manner that will not damage the cable.
This cable still needs to rise in a conduit to prevent mechanical damage before it enters the building. The visible conduit should be made of either galvanized steel or gray plastic, rated for the purpose.
How to Perform Residential Electrical Inspections 32
Where the service entrance cable is not rated for direct burial, it needs to be in a full conduit, and it must be buried at a minimum depth of 18 inches under landscape, and 24 inches under hardscape, such as driveways.
Where the service conductors are buried underground, they are required to have a ribbon embedded 12 inches above the conductor, unless they are under the exclusive control of the utility company.
In residential construction, there would be only one conduit.
The home inspector should evaluate any visible above-ground conduits and report any damage or open joints that would allow moisture into the assembly.
Electrical Meters and Bases
The electric meter is not normally part of the service entrance equipment. It is there to measure the
amount of power used on the property. Some properties may have more than one meter, maybe due to multiple occupancy or discounted power for heating use.
As the meter is a rated component like any other, the ampacity of the meter and its base cannot be lower than the stated total available amperage. We will look at this further in the next section.
Service Entrance 33
As meters have increased in capacity over the years, the meter bases have changed. The very earliest meters had no separate base, and are typically rated for only 30-amp supply.
• Round meter bases: Common from the 1920s up to the 1950s, they were rated for only 60 amps and are still often seen at older properties.
• Square meter bases: Typically found on homes from the 1950s to 1970s, these are still used in some smaller housing units (such as apartments) and were rated for only 100-125 amps.
• Rectangular meter bases: These are the current minimum on single-family homes. They are rated for 200 amps and typically bear the marking “200 CL.”
Understanding meter bases is an important part of being able to properly evaluate the maximum available amperage in the home, but they should not be solely relied upon when sizing a service.
Service Entrance Cable
The service entrance cable (SEC) is the conductor assembly that connects from the service supply, through the meter socket, and on to the primary service disconnecting means.
Obviously, the conductors are another rated component, and the home inspector needs to be familiar with the current-carrying capacity of the various sizes of cables.
How to Perform Residential Electrical Inspections 34
Service entrance conductors, like all others, are made from either copper or aluminum. As discussed previously, aluminum conductors need to be sized larger than copper ones for any given amperage.
Aluminum terminations may also be coated with an anti-oxidant to prevent corrosion, although the more recent AA-8000 aluminum alloy conductors do not require it.
The use of copper is most common, since it is the default conductor by code, but aluminum is popular for services when cost is an issue.
Service Entrance Conductor Ampacity
The table to follow shows the common cable sizes for both copper and aluminum, together with their ampacity and wire size.
|Service Amperage||Solid Wire Diameter in Inches||Copper Conductor||Aluminum Conductor|
|30 amps||0.102||10 AWG||8 AWG|
|60 amps||0.162||6 AWG||4 AWG|
|100 amps*||0.204||4 AWG||2 AWG|
|110 amps*||0.229||3 AWG||1 AWG|
|125 amps*||0.258||2 AWG||1/0 AWG|
|150 amps*||0.289||1 AWG||2/0 AWG|
|175 amps*||0.325||1/0 AWG||3/0 AWG|
|200 amps*||0.365||2/0 AWG||4/0 AWG|
|225 amps*||0.410||3/0 AWG||250 kcmil|
|250 amps*||0.460||4/0 AWG||300 kcmil|
|300 amps*||0.500||250 kcmil||350 kcmil|
|350 amps*||0.592||350 kcmil||500 kcmil|
|400 amps*||0.632||400 kcmil||600 kcmil|
Service Entrance 35
Increasing gauge numbers provides decreasing wire diameters. For example, when the diameter of a wire is doubled, the AWG decreases by 6. The AWG sizes are for single, solid, round conductors. The AWG of a stranded wire is determined by the total cross-sectional area of the conductor, which determines the current-carrying capacity and electrical resistance. The stranded wire is about 5% larger in overall diameter than a solid wire of the same AWG.
* 100-amp to 400-amp services are based on 3-wire, 120/240-volt systems, and 310.15 (B)(6) of the NEC®.
AWG = American wire gauge, also known as the Brown & Sharpe wire gauge, is a standardized wire gauge system used in the U.S. and Canada. “AWG” is referred to as a gauge, and the zeroes in large wire sizes are referred to as “aught.” Wire sized 1 AWG is referred to as “one gauge” or “No. 1” wire. Smaller-diameter wires are called “x gauge” or “No. X” wire, where x is the positive-integer AWG number. No. 0, written 1/0, is referred to as “1 aught” wire. 2/0 is referred to as “2 aught,” and so on.
kcmil = This wire size is the equivalent cross-sectional area in thousands of circular mils. A circular mil is the area of a circle with a diameter of one-thousandth (0.001) of an inch. In North America, conductors larger than 4/0 AWG are typically identi!ed by kcmil.
How to Perform Residential Electrical Inspections 36
1. Which of the following would describe most residential services?
110/220-volt 120/240-volt 240-volt only 120-volt only
2. A service entrance with four connected conductors is a ________ supply.
120-volt only 3-phase
3. The service drop should not pass closer than _____ to the bottom, front or sides of a balcony.
3 feet 4 feet 5 feet 6 feet 8 feet
4. The minimum service drop clearance over a $at roof used as a roof garden is _______.
8 feet 10 feet 12 feet 18 feet
5. Service drops around a swimming pool should be _______.
10 feet above and 22 feet horizontally away 18 feet above and 10 feet horizontally away 10 feet above and 20 feet horizontally away 22 feet above and 10 feet horizontally away 15 feet above and 8 feet horizontally away
12 feet above and 15 feet horizontally away
6. Service drops should never pass closer than ________ above the ridge of a conventional pitched roof.
3 feet 5 feet 8 feet
7. Tree limbs should be trimmed back to ________ away from the service drop.
1 to 2 feet 2 to 3 feet 4 to 5 feet 5 to 6 feet
8. An electrical service mast that extends more than ______ above the roof surface should be separately supported.
3 feet 4 feet 5 feet 6 feet
9. Which of the following may also be supported by the electrical service mast?
all of these
telephone cables satellite dishes none of these clothes lines
10. Rigid service masts should be secured to the structure every _______.
2 to 3 feet 3 to 4 feet 30 inches 5 to 6 feet
11. Which type of cable is listed for direct burial?
12. An underground service entrance is called a ________.
How to Perform Residential Electrical Inspections 38 13. Square electric meter bases are indicative of a _________.
150-amp supply 60-amp supply 100-amp supply 30-amp supply
14. Most modern 200-amp electrical meters are marked __________.
200 CL 200 UL 200 SEC 100 CL 100 UL 100 SEC
15. The minimum conductor size for a 100-amp service is ___________.
2 AWG copper or 4 AWG aluminum 4 AWG copper or 2 AWG aluminum 2 AWG copper or 1 AWG aluminum 1 AWG copper or 2 AWG aluminum
Answer Key is on page 106.
Grounding and Bonding 39 Grounding and Bonding
What Is Grounding?
Grounding is a direct connection to the earth to aid in removing damaging transient over-voltages due to lightning. The purpose of bonding is to ensure the electrical continuity of the fault current path, to provide the capacity and ability to safely conduct any fault current likely to be imposed, and to aid in the operation of the over-current protection device. Properly bonding all metal parts within an electrical system helps ensure a low-impedance fault current path.
The issue of grounding and bonding confuses many inspectors. Due to its complexity, in this section, we will try to break it down to its fundamentals, and look at the basic requirements and common failures that can lead to unsafe conditions around the home.
To go back to the beginning, the last stop on the utilities distribution chain, before the supply goes to the home, is the transformer. This steps down the high-voltage primary distribution to the neighborhood, and to the 240/120-volt feeds to the homes.
The transformer has a winding known as a phase coil that is center-tapped to provide voltage stabilization, and a return path for the higher voltage system to aid in clearing primary side faults.
As discussed earlier, on a typical 240/120-volt service drop, there should be two ungrounded conductors and a single grounded conductor.
This means that we have to establish our own grounding electrode system at the dwelling. It is vital in removing dangerous voltages imposed on the system via lightning strikes and over-voltage surges from higher voltages on power lines. If ground-rod, pipe or plate electrodes are used, they must have a rating of 25 Ohms or less; otherwise, an additional electrode must be added, per Section 250.56 of the NEC®.
How to Perform Residential Electrical Inspections 40
There are several methods of connecting the grounding system to the ground, with a driven rod being the most common in most areas. Most residential construction requires two separate grounding electrodes in any combination of the following (which need to be at least 6 feet apart):
• driven rods;
• metal water pipes; • well casings;
• Ufer grounds;
• ground plates;
• steel framing; and • ground rings.
Historically, the grounding system had just one connection to ground, and this was nearly always made on the water supply pipe. However, two connections are now required by most jurisdictions to ensure a low-impedance ground (one with little resistance).
Because most utility companies now install plastic potable water supply lines, a water pipe cannot be used as a grounding means, so one of the other electrodes listed must be used. It is also important to note that all electrodes that are present in the dwelling must be bonded together to form a single and complete grounding electrode system.
Typically, the two required grounding electrodes need to be at least 6 feet apart. If one is the water pipe ground and the supplemental is a ground rod, another ground rod may need to be added in order to meet the requirements of section 250.56 of the NEC®.
Gas piping CANNOT be used as a grounding electrode for safety reasons, but, in most areas, gas lines are required to be bonded to the grounding system if they are likely to become energized.
Driven Rods 5/8-Inch Diameter
Rods made of stainless steel and copper, or zinc-coated steel, shall be at least 5/8-inch in diameter. Grounding electrodes of pipe and conduit must be at least 3/4-inch (metric designator 21). There are special listed rods, and listed rods may not be less than 1/2-inch in diameter. If pipe or conduit is used as a grounding electrode, it must also be no less than 8 feet in length, and no smaller than trade size or 3/4-inch.
If a micrometer or similar device is not available, the home inspector shouldn’t guess the rod’s diameter. If visible, you may be able to con!rm the diameter by looking at the listing marks, which may indicate that the rod complies with the diameter requirements of the National Electric Code® (NEC®). The listing agencies CSA, ETL, MET, and UL will mark rods that are greater than 1/2-inch in diameter and that have the correct minimum amount of coating.
Grounding and Bonding 41
8 Feet in Length and in the Soil
Rod and pipe electrodes must be at least 8 feet in length to be considered a grounding electrode.
All rods should be driven 8 feet into the earth. The rod and pipe electrodes must be installed at least 8 feet of length in direct contact with the soil, in the ground. They must be driven into the ground at least 8 feet. They could be driven at an angle, but the angle should not be more than 45 degrees o the vertical. Or the rod could be buried in a trench that is at least 30 inches deep.
Sometimes, in very rocky earth, the rods cannot be driven perpendicular to the ground, so they may be driven at an angle of less than 45 degrees. If they cannot be driven at all due to unfavorable soil conditions, they can be installed in a trench no less than 30 inches deep. But no part of any grounding electrode can be closer than 6 feet to any other.
The upper end of the electrode should be $ush with the ground or just below the ground surface so that the end and attachment are protected from damage. If you !nd a rod sticking up out of the ground, that’s a defect. It should be at or just below the soil surface.
Pipe or conduit made of steel shall have an outer surface that is galvanized or otherwise metal- coated to resist corrosion. If the material is iron or steel, the electrode must have its outer surface galvanized or metal-coated for corrosion protection.
The ground wire (the grounding electrode conductor) needs to be fastened (referred to as the attachment) with the correct approved clamp, and the attachment needs to be rated for direct burial, if located below ground. It is common to see these “acorn” clamps installed improperly, with the conductor clamped under the screw rather than to the solid part of the clamp, which has the biggest contact area.
Metal Water Pipes
As discussed, these were the most common connections at one time, with all homes being connected with metal piping.
Where the metal pipe is used as a grounding electrode, the conductor should be connected with clamps rated for water tubing, and it needs to be connected within the !rst 5 feet of piping as it enters the structure.
Since the water meter is a removable part of this potential circuit, a jumper cable needs to connect the pipework on either side of the meter to ensure continuity at all times.
Jumper at the Water Meter
A jumper or bonding conductor is a conductor used to ensure that there is electrical conductivity between metal parts that are required to be electrically connected. For example, a jumper may be installed over the water meter because the continuity of the grounding path or bonding connection of the interior pipes should not rely on the water meter. The jumper is a large-gauge conductor that
“jumps” over the water meter and is securely attached to the metal water pipe on each side.
How to Perform Residential Electrical Inspections 42
As wells are bored to a great depth and lined with metal sleeves, they make good grounding electrodes, as long as they are far enough away from other grounds and are properly connected.
More properly referred to as a concrete- encased electrode, the Ufer ground is named after Herbert George Ufer, a retired Underwriters Laboratories vice president, who developed the system during WWII to help ground concrete armament bunkers.
With so many homes and commercial buildings now built on concrete steel- reinforced slabs, this grounding system has become very common.
The requirements for Ufer grounds are that they have either 20 feet of #4 rebar, or 4-AWG copper wire encased in at least 2 inches of concrete within the footer that is in contact with the earth.
This system must also have an external means of connecting other grounded systems to it, such as telephone wires.
In some cases, ground plates are used as the grounding system, but this is uncommon in residential construction.
Ground plates made of ferrous metal (such as iron or steel) shall have a thickness of no less than -inch. Plates made of non-ferrous metal should have a thickness of no less than 0.06 inches. They
should be at least 2 square feet in overall size and be buried to a depth of 30 inches.
Steel-framed buildings typically use the frame as one of the grounding electrodes, as long as the structure is substantial enough and has at least 10 feet of connection to the earth. Most commonly, the framing is connected to an Ufer ground.
Again, although it’s very rare in residential construction, a ground ring may be installed where a minimum 2-AWG conductor is buried to a depth of at least 30 inches right around the structure.
Grounding Electrode Conductors
The GEC is the conductor that connects to the grounding electrode, and its size is dictated by the size and, therefore, the amperage of the service conductors. The table below shows the sizes.
Grounding and Bonding 43
|Copper SEC Size||Aluminum SEC Size||Copper Grounding Electrode Conductor Size||Aluminum or Copper- Clad Aluminum Grounding Electrode Conductor Size|
|2 AWG or smaller||1/0 AWG or smaller||8 AWG||6 AWG|
|1 or 1/0 AWG||2/0 or 3/0 AWG||6 AWG||4 AWG|
|2/0 or 3/0 AWG||4/0 or 250 kcmil||4 AWG||2 AWG|
|over 3/0 to 350 kcmil||over 250 to 500 kcmil||2 AWG||1/0 AWG|
|over 350 to 600 kcmil||over 500 to 900 kcmil||1/0 AWG||3/0 AWG|
|over 600 to 1,100 kcmil||over 900 to 1,750 kcmil||2/0 AWG||4/0 AWG|
|over 1,100 kcmil||over 1,750 kcmil||3/0 AWG||250 kcmil|
Remember: The GEC should be connected only to the neutral at the service panel (the panel containing the service disconnect) and no where else.
Bonding of Components
The purpose of bonding is to ensure the electrical continuity of the fault current path, provide the capacity and ability to safely conduct any fault current likely to be imposed, and to aid in the operation of the over-current protection device.
As discussed in the section on panel enclosures, they need to be bonded to the grounding system. But there is also a very long list of other components that need to be connected to ground, since they have the potential to become energized to electrical faults.
These components include:
• interior water piping; • water heaters;
• around water meters; • gas lines;
• electrical enclosures; • electrical raceways;
• electrical outlets;
• junction boxes;
How to Perform Residential Electrical Inspections 44 • CSST gas piping (per the manufacturer’s compliance); and
• telephone and cable TV systems.
In more modern panels, the bonding connector is required to be through an approved green screw so it is more apparent to both the electrician and the code enforcement ocer.
However, in many panels, there may be a bonding strap or bonding bar.
Panels and Enclosures
NOTE: All conductors in image above shown as copper.
Remote Distribution Panels
Although this topic is covered in other areas, because the emphasis of the electrical portion of a home inspection is on safety, it’s important to review.
The National Electrical Code® (NEC®) does not recognize the term “sub-panels.” From a code standpoint, there are two types of panels: service panels and distribution panels.
A service panel is a distribution or load center that contains the main disconnecting means. This is the only panel where the neutral and grounds should be joined (bonded) together.
Grounding and Bonding 45
Distribution panels, or load-side panels, are downstream from the panel containing the main service disconnect(s). In these panels, the neutral and grounds should be separate, and the neutral bus should be isolated from the panel enclosure.
The only exception to this is in existing detached structures where no metallic path exists between the structures. In this exception, a connection between the grounded conductor and the metal case via a bonding jumper is permitted. According to the 2008 NEC®, this is not allowed in new construction, so, in all cases, a 4-wire feed to the detached structure is required in order to isolate the grounded conductors from the equipment grounding conductors.
There are two methods of providing ground continuity back to the service panel:
1. four conductor feeders with:
• two hot or ungrounded conductors;
• one neutral or grounded conductor; and • one equipment grounding conductor.
2. three conductor feeders with:
• two hot or ungrounded conductors;
• one neutral or grounded conductor; and
• equipment grounding through conduit/tubing, electrically linking the two panels (allowed by section 250.118 of the NEC®).
Inspecting Service Panels
Here are three essential items to inspect for:
1. Are the neutral and ground connected (bonded)?
2. Is the panel enclosure connected (bonded) to ground?
3. Does each neutral conductor terminate at a separate lug on its bus?
Inspecting Distribution Panels
Here are !ve essential items to inspect for:
1. How is the service grounded back to the service panel? 2. Are the neutrals and grounds separated?
3. Is the neutral bus isolated from the panel enclosure?
4. Is the panel enclosure connected (bonded) to the grounding bus? 5. Does each neutral conductor terminate at a separate lug on its bus?
Every structure is required to have a grounding electrode system. If grounding electrodes are present in the structure, they must all be bonded together. If a detached structure has a remote distribution panel located at the structure, then it requires a grounding electrode system of its own. The equipment grounding conductor in a 4-wire feeder does not take the place of the required
How to Perform Residential Electrical Inspections 46
grounding electrodes. It is also important to understand that if the detached structure is being
fed by a single branch circuit, and it contains an equipment grounding conductor that is used for grounding the non-current-carrying metal parts of equipment, then no grounding electrode system is required.
The inspector should pay very close attention to the grounding and bonding of all electrical circuits. Sometimes, it is very hard to !gure out which components are electrically connected to others.
Do not disturb conductors in the panel! The inspector is limited to a visual inspection only. Probing around inside energized panels may cause loose conductors to become detached, or result in electric shock.
When in doubt, defer to a licensed electrical contractor.
1. Most jurisdictions require _____ separate grounding means.
one two three four
2. The minimum size for a stainless steel, unlisted driven grounding rod is _______.
5/8-inch diameter and 6 feet long -inch diameter and 8 feet long -inch diameter and 6 feet long 5/8-inch diameter and 8 feet long
3. T/F: Driven grounding rods can only be perfectly vertical.
4. Which of the following cannot be used as a grounding means?
gas supply piping well casings
5. T/F: Only panel enclosures containing the service disconnect need to be bonded to ground.
6. The grounded and grounding conductors can share a common bus only in ________.
the service panel
any electrical panel the distribution panel
7. The ungrounded and grounding conductors can share a common bus ____________.
in any distribution panels
in the downstream distribution panels in the service panel
How to Perform Residential Electrical Inspections 48 8. Which of the following is an acceptable means of bonding a remote distribution panel?
connecting the enclosure to the grounding bus
connecting the enclosure to the ungrounded conductor bus connecting the enclosure to the neutral bus
9. Conductors between the main service disconnect and the distribution panels are called __________.
runners feeders travelers
Answer Key is on page 107.
Service Panels 49
The Main Disconnect The Service Disconnect
All electrical systems require a means of disconnection so that the service can be shut down quickly if any dangerous conditions exist. In this section, we will look at the types of disconnects, and the common problems that need to be reported.
The service equipment is the necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load-end of service conductors to a house, and intended to constitute the main disconnecting means for service. The disconnecting means for service should be located outside or inside the house as close as possible to the point of entrance of the service conductors. The service equipment must be identi!able and marked as a service disconnect. A common service size for a single-family house is 200 amps. And the main
200-amp breaker located at a main panelboard would be the main disconnect for the service.
It is required that the entire electrical supply to the home is able to be shut o with six or fewer moves of the hand. This can be in the form of one or more knife switches, one or more fuses or fuse blocks, or, most commonly and in more recently built homes, by throwing the breaker(s).
If the supply cannot be disconnected from one location in this manner, the home inspector should report that the system is in need of repairs or upgrade.
Types of Disconnect
As discussed, dierent systems are in common use today, depending on the age of the property:
• knife switch: This is the oldest type of disconnecting means. We all remember the old horror movies where Dr. Frankenstein was shown energizing his creation. The switches he used were knife switches.
• fuse blocks: Often called mains and range panels, the electrical supply is shut down by pulling the two fuse blocks from the panel.
• breaker(s): This is the most common type of
disconnect. Throwing one or more breakers shuts o the electrical power. In most cases, we see a single main breaker, but there are “split-bus” panels where the homeowner would need to trip several breakers to achieve a total shut-down.
Again, the rating (or fuse or breaker size) of the disconnect relates to the total amperage available within the home. For example, if the main disconnect is rated at only 100 amps, it doesn’t matter that the SECs are rated for 200 amps.
In many homes, and in nearly all mobile or manufactured homes, the service disconnect is not in the main distribution panel.
This is not a problem, but care must be taken to fully investigate the grounding and bonding of all downstream distribution panels, as will be covered later.
How to Perform Residential Electrical Inspections 50
As discussed, some panels are of a split-bus design, which means that the bus bars that the breakers draw power from do not extend right through the panel.
Normally, these panels have multiple double-pole breakers at the top of the panel controlling the typical 240-volt circuits, such as for a clothes dryer, stove, and air-conditioning unit.
However, on these panels, one of these double-pole breakers also shuts down power to the lower parts of the bus, which controls the individual 120-volt branch circuits.
The photo above shows an antiquated fuse disconnect.
Notes on Mains and Distribution Panels
Remember that the panel with the main disconnect is the service panel, and panels downstream (or on the load side) of the service panel are remote distribution panels. Neutrals and grounds should be bonded together only in the service panel, and not in any downstream remote distribution panels.
This will be covered in more detail later.
Service Amperage Service
For houses serving one family, the ampacity of the ungrounded service conductors shall be a minimum of 100 amperes, 3-wire. For all other installations, the ungrounded conductors should have an ampacity of at least 60 amperes. The ungrounded service conductors should have an ampacity of at least the size of the load served.
Reporting the Main Service Disconnect’s Amperage Rating
According to InterNACHI’s Standards of Practice, the inspector shall describe the main service disconnect’s amperage rating, if labeled. That’s all a home inspector needs to do here. Reporting the disconnect’s amperage rating is important for two reasons. First, an older home may not have enough power for a modern family’s needs. Second, many insurance companies will not insure a property having less than a 100-amp service.
As illustrated in the section on meters, electrical services have gotten much bigger since we !rst started wiring homes for electricity over 100 years ago. When homes were !rst wired for power,
Service Panels 51 there were few electrical devices available, so a couple of 15-amp lighting circuits, and maybe a
radiogram outlet, were all that was needed.
In homes today, nearly every room has multiple electronics and appliances in it, and we need high- amperage 240-volt circuits to run larger ones, such as central air conditioning and electric clothes dryers.
Development of Power Needs
The list below is intended to be no more than a rough rule of thumb covering the average unimproved electrical supply over the last century, and would cover the average 1,500- to 2,000-square-foot home:
• 1900s to 1930s: 30-amp supply
• 1930s to 1950s: 60-amp supply
• 1950s to 1970s: 100-amp supply • 1970s to 1980s: 150-amp supply • 1980s to 2000s: 200-amp supply
Obviously, larger and more expensive homes have always required more power than the norm, and it is not unusual now to see 400+-amp services in high-end homes.
Calculating Available Amperage
In many cases, the listing information about a home is incorrect regarding the service amperage because brokers or owners rely solely on the size of the main breaker or fuse. Many people are also under the mistaken impression that the available amperage is the total of the individual breakers or fuses in the service panel.
The correct way to determine the available amperage is to determine the ampacity of the lowest- rated or the weakest link of the following components:
• service supply;
• electric meter and socket;
• service entrance conductors; • service disconnect; or
• distribution panel.
Here are a couple of examples:
• 200-amp service lateral
• 200-amp meter and base
• 175-amp-rated SEC
• 150-amp-rated panel
• 125-amp labeled service disconnect
A home inspector should describe the main service disconnect’s amperage rating.
How to Perform Residential Electrical Inspections 52
• 150-amp service drop
• 60-amp identi!ed meter and base • 150-amp SEC
• 100-amp-rated panel
• 100-amp labeled service disconnect
A home inspector should describe the main service disconnect’s amperage rating. The home inspector may also describe the 60-amp meter as a potentially inadequate that should be further evaluated by a licensed electrician.
A home inspector is not an electrician. A home inspector must be careful in describing total amperage service supplied to the house. A home inspector must follow the Standards of Practice, and be careful in exceeding those Standards.
Please refer to the electrical section of InterNACHI’s Standards of Practice.
Inspecting Enclosures, Part 1
Reportable Panel Issues, Part I
All panels and enclosures, regardless of their purpose, should be inspected for the following safety- related issues. Any de!ciencies should be reported as in need of repair or replacement by a licensed electrical contractor.
All of the following are related to safety:
• compromised panel access; • missing knockouts;
• missing bushings;
• signs of arcing;
• incorrect dead-front screws;
• incorrect panel listings (UL ratings); • missing legend;
• damaged breakers; and
• improper panel bonding.
As can be seen in the image above all electrical-related panel locations have to provide adequate access for servicing. They should be on a free wall space not less than 30 inches wide, have a clear space of 36 inches in front of them, and have 6 feet and 6 inches of headroom. The panel is not required to be centered in this space. In existing homes with a service of 200 amps or less, a reduction in headroom is permitted by Section 110.26 (E) Ex. of the NEC®.
In older homes, it is also common to !nd electrical panels inside closets. This is no longer
Service Panels 53 acceptable in new construction. Similarly, service disconnects and remote distribution panels are
not allowed in bathrooms.
The home inspector will frequently see installations that are restricted by stored items, or other systems have been installed in front of the panel.
There should be no access into the panel whatsoever. This is to prevent accidental electrocution by someone being able to put a screwdriver or a !nger into the panel and touch a live component.
However, we frequently see holes where wiring has been changed, or where breakers have been swapped around. All of these should be reported as safety issues, with repairs recommended.
It is also common to see upgrades where the old panel has been relegated to the role of a junction box, but all breaker holes are still open.
Anywhere a cable or cable assembly enters a panel or other enclosure, there should be a connector.
This is designed to do two things: !rst, to locate the cable securely (called strain relief); second, to protect the cable from cha!ng against the enclosure itself.
In many cases of homeowner wiring, we will see no connector present at all, or an unlisted item being used.
How to Perform Residential Electrical Inspections 54
Inspecting Enclosures, Part II
Reportable Panel Issues, Part II
Moisture In or On Panels
A crucial point to always bear in mind is that water is a very good conductor of electricity. Any panel that is damp or wet should not be opened by an inspector.
Before even thinking about removing a dead front, the inspector should look carefully for signs of water or moisture staining on the panel or on its surrounding wall.
As we saw with the service entrance, any failures of the mast or cable entryways may result in water getting into the panel. If there is any evidence of water, the inspector should recommend that the panel be fully evaluated and repaired by a licensed electrical contractor, so delving further into the panel is not only potentially dangerous, it’s also unnecessary.
In the image at right, extensive water damage can be seen around the panel.
It goes without saying that any panel or enclosure showing rust has been exposed to a high level of moisture. It may well be that a previous leak has been repaired, but the inspector should be extremely cautious of investigating the panel further.
Remember: The inspector’s primary goal is to maintain his own safety and that of his clients.
There are several issues related to circuit breakers:
1. Are they rated for the model of panel they are installed in?
Service Panels 55 2. Do they have their handle ties in place on double-pole breakers so that both sides of the circuit
can be shut o at the same moment?
3. Are there any signs of arcing, burning or smoke damage that would indicate that the breaker is not tripping as intended?
We will look at these issues in more detail later.
Signs of Arcing
As part of the initial visual inspection of a panel, the inspector should look closely for any signs of arcing or burn marks on the panel. Again, these may be the result of previously repaired problems, but don’t count on it. Also, take a second to listen to the panel because, in many cases, you may hear arcing.
Inspecting Enclosures, Part III
Reportable Panel Issues, Part III
Incorrect Dead Front Screws
As was discussed for arcing issues, many faults related to damage to conductors inside the panel are caused by either the wrong screws being used, or the correct screws running up against the live conductors and causing a dead short against the panelboard.
Arcing or smoke damage on the outside of the panel is obviously indicative of a previously signi!cant and dangerous condition. It is recommended that, at a minimum, the inspector ask the homeowner for details of the damage and its repair prior to opening the panel.
Remember that there are many issues that can lead to this kind of telltale marking, and many of those can lead to the panelboard being live, or short circuits being caused by removal of the dead front.
The result is that an arc $ash
vaporizes the steel of the screw
and panel (or the copper of the
conductor) and can send a cloud of molten metal and sparks straight out.
That’s why the inspector needs to be wearing safety glasses and cotton clothing.
How to Perform Residential Electrical Inspections 56
All fuse or breaker panels are required to have an accurate listing of what the circuits are connected to. This is called a legend.
An unsafe condition can exist if the homeowner turns o a breaker, believing to have killed
the power on the circuit, only to !nd that s/he tripped the wrong breaker. For this reason, any de!ciencies in the labeling of panels should be noted, with the client made aware of the need for this to be recti!ed.
The legend is sometimes printed out by the installing contractor and stuck to the panel cover. It’s more typical, however, that the legend is missing, incomplete, inaccurate or illegible.
Like any other components, panels are rated or UL-listed (by the Underwriters Laboratories). Every panel must carry a label explaining where it can be used, what it can be used for, how many circuits it can support, and, most importantly for inspectors, the maximum amperage it can support.
In many cases, these panel markings are obscured, but, wherever possible, the home inspector should attempt to check the labels to ensure that the panel is rated for the correct amperage.
While looking at general panel conditions, the inspector should pay attention to the requirements for all panels to be bonded to the grounding system.
This ensures that any electricity that is imposed onto any metal parts of the electrical system is safely transferred to the grounded conductor, and, in the case of a fault condition, allows the over- current protection device to activate properly. In applications where the grounding bus is screwed directly to the panel, this connection is already there.
Where the grounds and neutrals (grounded conductors) share a bus, a bond should bridge between that bus and the enclosure.
If the ground bus is isolated from the enclosure (for example, by an insulated plastic bushing), a bonding jumper needs to be installed between the bus and the metal enclosure.
In all cases, look for a green-headed screw signifying that the panel is bonded.
Edison Base Screw Fuse Panels
Service Panels 57
These panels were universal from the earliest days of electricity in the home, right up to the 1950s when breaker panels started to appear in residential construction. Many homes built up until the late 1960s still had fuse panels.
Fuse panels are generally seen as being more reliable than breaker panels because of the fact that they will always blow when overloaded, either by loads imposed on them or under dead-short conditions. Breakers, on the other hand, have been known not to trip at the speci!ed amperages.
Many insurance companies, however, will either not insure these homes that still have fuse panels, or will insure them at higher premiums. This is not due to any danger from the fuses themselves; rather, it is indicative of a generally older, unimproved system which, statistically, is more likely to produce an electrical !re.
Many fuse-style panels use a fuse block as both the primary over-current protection and also as the disconnecting means. These Bakelite blocks contain two cartridge (or “shotgun shell”) fuses.
This block (or blocks) must be pulled to disconnect the power to the home. These fused panels are normally rated at either 60 or 100 amps.
Main and Range Panels
Many homes from the 1930s onward used main and range panels. These have two fuse blocks: one acting as the main disconnect and primary over-current device, and a second block supplying power for the electric range. These became very common.
Some fuse panels may contain as many as four fuse blocks, commonly having one as the main disconnect, with the others supplying other 240-volt circuits for large appliances, such as a range, air-conditioning equipment, clothes dryer, and even other distribution panels.
In all cases, all the blocks must be removed to completely disconnect all the power to the home.
Edison Base or Plug Fuses
These are the fuses that screw into many older panels and have the same thread that Edison used for other applications, such as the common light bulb. This obviously creates a problem, since
a higher-amperage fuse can be screwed into a location supporting lower-amperage conductors, eectively turning the conductor into the fuse (not a great idea).
The inspector should recommend the installation of S-type fuses and adapters to ensure that the circuits cannot be overloaded. These adapters screw into the standard fuse location and reduce the thread size down. Various sizes are available (from 15 to 30 amps) and allow only the correct amperage type-S fuse to be installed. These adapters are designed so that, once installed, they
Inspecting Fuse Panels
How to Perform Residential Electrical Inspections 58
cannot be removed.
They also have the added bene!t of stopping someone from repairing a blown fuse by putting a penny under the blown fuse, which is an old practice.
It is common to see over-fused circuits on older fuse panel installations. The inspector needs to remember that, in most of these cases, the installation was designed to supply a relatively small number of circuits with few receptacles. That would have been !ne for the average family’s needs in the 1950s and 1960s, but that’s now exceeded by modern demands.
Several types of fuses are available. Some blow very quickly, while others are designed to cope with short, extra start-up loads associated with electric motors. These will blow after a short time if the amperage draw does not revert to normal levels.
As discussed earlier, there are two major problems with inspecting older fuse panels. First, check the main fuse amperages. The blocks have to be pulled out, which shuts o all power to the home. The second problem is that these panels tend to be unsuitable for modern, high-amperage demands, and they tend to exhibit double taps and over-fusing.
Pay special attention to the following questions during an inspection:
1. What is the main fuse rating?
2. Are there double taps?
3. Does the rating of the fuse match the conductors?
4. Are the fuses updated to S-type?
5. Is there any sign of conductors overheating?
Service Panels 59
Breaker Panels and Breakers Circuit Breaker Panels
These are probably the most common types that home inspectors will come across, as they have replaced fuse panels over the last 40 years or so. As we saw for fuse panels, breakers are far from foolproof and require some particular checking.
Breaker panels go farther back than many people realize, having been patented in 1910. However, it is unusual to see a residential breaker panel from before WWII. Prior to this, electrical breakers were primarily used in manufacturing and naval applications.
Breaker panels started appearing in homes in the mid-1950s in small numbers, and were universal in most areas by the late 1960s.
As discussed, they did not replace fuses due to any de!ciency of the older technology. The problem was that when a fuse blew, one needed to go
!nd a replacement. Breakers are obviously more convenient because when they trip after a fault, they can be reset without replacement.
We now have added bene!ts from circuit breakers with the advent of both GFCI and AFCI protection, in many locations.
120-Volt Circuit Breakers
How to Perform Residential Electrical Inspections 60
Breakers fall into four categories, which we’ll look at in more detail:
1. 240-volt pole breakers; 2. 120-volt single breakers; 3. GFCI breakers; and
4. AFCI breakers.
All of these require some specialized knowledge to properly evaluate. Remember that we’re talking about energized components. Safety is paramount when investigating electrical panels.
240-Volt Circuit Breakers
Most homes now require circuits of greater capacity and higher amperage to run large appliances, such as clothes dryers, air-conditioning units, stoves, and some load-side distribution panels, etc.
Appliances that are 240-volt are fed from two 120-volt conductors, with each connected to a separate bus bar in the distribution panel. It is imperative that when one of the circuits trips due to an over- current condition, both conductors be de-energized at the same time. If not, someone could be trying to repair an appliance that is still partially live.
For this reason, all breakers supplying 240 volts are required to have the handles tied together by an identi!ed handle tie. Nails, screws, or scraps of wire, for example, are unacceptable. Sometimes, the breaker is molded with this connection in place, and sometimes they are linked by a listed handle tie. The inspector should ensure that the tie is present and has not been damaged.
A 240-volt circuit breaker also acts as the main disconnecting means in modern panels, which can disconnect all the electrical power in the home.
Regular 120-volt circuits are fed from one bus bar only. Also in use are tandem breakers, which are 120-volt breakers that feed two separate circuits, each controlled by its own handle. (These should not be linked.) As with fuses,
the inspector should ensure that the rating of the breaker does not exceed the rating of the conductors, unless allowed by 240.4 (E) or (G) of the NEC®. Otherwise, something other than the breaker is likely to overheat and fail.
There are two manufacturers of single-pole, 120-volt breakers who have their products listed for two conductors. These are made by Square D and Cutler-Hammer. These should not be confused with double-tapped breakers, where more than one conductor has been incorrectly connected to a single breaker.
Service Panels 61
Ground-fault circuit-interrupting breakers are one way to protect circuits and their users from ground faults. Not all circuits are required to have GFCIs and, in many homes, the locations that require this protection have their own GFCI outlets. However, if a GFCI breaker is used, it will provide protection to all receptacles in that branch circuit.
GFCI breakers feature trip and reset buttons to ensure that they are working properly. The inspector should trip the breaker using the test button and ensure that the circuit has indeed been switched o.
Arc-fault circuit interrupters have been required in
new construction since the 1999 edition of the NEC®. Many jurisdictions are now observing the 2008 edition, which has expanded the use of AFCI devices to nearly everywhere within a dwelling except the kitchen, bathroom, and most areas where GFCI protection is already required. These breakers are designed to trip
if they sense arc faults in the circuit, which are caused primarily by damaged wiring.
What Is an AFCI?
Arc-fault circuit interrupters (AFCIs) are special types of electrical receptacles or outlets and circuit breakers designed to detect and respond to potentially dangerous electrical arcs in home branch wiring. As designed, AFCIs function by monitoring the electrical waveform and promptly opening (interrupting) the circuit they serve if they detect changes in the wave pattern that are characteristic of a dangerous arc. In addition to the detection of dangerous wave patterns (arcs that may cause !res), AFCIs are also designed to dierentiate safe, normal arcs. An example of this arc is when a switch is turned on or a plug is pulled from a receptacle. Very small changes in wave patterns can be detected, recognized, and responded to by AFCIs.
A Brief History
In the 1999 NEC®, these breakers were required only on bedroom receptacles. In the 2002 NEC®, the requirement was expanded to all 15-amp and 20-amp, single-phase, 120-volt branch circuit- supplying outlets. The 2005 NEC® expanded their use to allow AFCI devices similar to GFCI receptacles, but none existed on the market, and their use was limited by 210.12(B). Finally, in the
2008 NEC®, the use of combination-type AFCIs expanded to 15- and 20-ampere branch circuit- supplying outlets installed in a dwelling unit’s family room, dining room, living room, parlor, library, den, bedroom, sun room, recreation room, and similar rooms, including hallways and closets. Many people confuse the term “combination” to mean AFCI and GFCI together in a single device. This is partly correct only in that most AFCI devices oer Class B-type of GFCI protection, which usually starts at around 20 to 30 milliamps, and do not oer any personal protection as do conventional GFCIs.
The combination-type AFCIs are designed to activate when there is a parallel arc that reaches a peak
How to Perform Residential Electrical Inspections 62 of 75 amps. The “combination” refers to the fact that AFCIs now protect against series arcs, as well.
They have a 5-amp peak threshold. This is where the term “combination” comes from.
Remember that the term “outlet” is not interchangeable with “receptacle.” Outlets are de!ned by the NEC® as “a point on the wiring system at which current is taken to supply utilization equipment.” Recess lights, smoke alarms, receptacles within outlet boxes, and so on, are supplied from outlets.
It is likely that many more locations (maybe even the whole house) will be required to have arc-fault protection with future code revisions. As with GFCI breakers, these should also be tripped with their test buttons, and the circuit should be checked to make sure it has been shut down.
Inspecting Circuit Breakers
The inspector should pay special attention to the following questions and report any de!ciencies as in need of immediate repair:
1. Does the breaker exceed the capacity of the conductor?
2. Does the breaker have multiple incorrect “taps”?
3. Do the 240-volt breakers have their handles tied properly?
4. Do the GFCI breakers test and reset properly?
5. Do the AFCI breakers test and reset properly?
6. Is there any sign of overheating, arcing, or smoke damage on any of the breakers?
Panels Types to Be Aware Of
There are several makes of panels whose breakers are no longer available. Also, there are a couple of manufacturers whose panels are known to be problematic.
These are still fairly common. The breakers are of a “push-for-on,” “push-again-for-o” design. The issues with these tend to be:
1. lack of panel capacity;
2. sticking breakers; and/or
3. diculty !nding replacement parts.
While the panel may be in clean condition, the client should be advised that these older panels are fast becoming obsolete as replacement parts are becoming harder to !nd. Recommend that an upgrade may be in order, as well as a full evaluation by a licensed electrical contractor.
Federal Pacific Electrical
Service Panels 63
The problem with this brand is primarily with their Stab-Lok® range of panels and breakers. These featured stamped sheet metal or copper bus bars and breakers with thin copper tabs that were designed to lock into the bus. These have the unfortunate habit of falling out when the dead front is removed, and this has caught many newer inspectors by surprise.
Federal Paci!c panels were subject to warnings issued by consumer protection groups, which include:
1. loose breakers;
2. non-tripping breakers; and
3. arcing problems between the breaker and its bus.
While the panel may appear to be in good working order, the inspector should defer full evaluation of FPE panels to a licensed electrical contractor.
The earliest Zinsco panels had busses made of copper bars and were very reliable. However, during the copper shortages of the mid-1960s, the copper was replaced with anodized aluminum bars. This led to problems of poor contact between the breaker and the bus bar, and many have failed since then due to arcing between the components. The problems continued after Zinsco’s sale to Sylvania in the early 1970s.
Due to the frequent failure of the connection between the breaker and its bus, the inspector should recommend full evaluation and possible replacement of
the panel by a licensed electrical contractor.
How to Perform Residential Electrical Inspections 64
1. The minimum service amperage required for a newer single-family home is __________.
60 amps 200 amps 100 amps 150 amps
2. An electrical panel that uses a double-pole breaker to isolate the 120-volt circuits is called a ________________ panel.
Federal Pacific partial-bus
3. One should be able to shut down the electrical supply with _______ or fewer moves of the hand.
four five six seven
4. The available service amperage is based on _______________.
the total of all the branch circuit breakers the size of the service entrance
the size of the main disconnect
the lowest-rated component
5. Most homes constructed between 1930 and 1950 originally had a ______ service.
30-amp 40-amp 60-amp 100-amp
6. Which of the following would not be an electrical panel defect? lack of legend
rusted enclosures missing knockouts wire splices
7. Electrical service panels should be in a clear space measuring _______________.
30 inches wide by 78 inches high by 36 inches deep 36 inches wide by 78 inches high by 30 inches deep 30 inches wide by 78 inches high by 30 inches deep 36 inches wide by 78 inches high by 36 inches deep
8. Electrical panels do not have to be fully enclosed as long as no hole is bigger than _________.
none of these
9. T/F: Water dripping from an electrical panel should be fully investigated by the home inspector.
10. A common cause of arc $ashes when removing panel fronts is __________.
11. Which of the following should the inspector be wearing while evaluating electrical panels?
all of these
none of these
non-synthetic clothing safety glasses
12. Which of the following should be reported as a problem with an electrical panel?
pigtails (two wires joined to a common breaker) splices in the panel
unlinked double-pole breakers
How to Perform Residential Electrical Inspections 66 13. A(n) ___________ connection should connect the grounding bus to the electrical enclosure.
bonding jumper grounding earthen
Answer Key is on page 107.
Service Panels 67
Phased Supply and Distribution
As discussed earlier, 3-phase supply is common in commercial, agricultural, and some apartment properties. Evaluation of these panels is well beyond the scope of most home inspections and should be deferred to a specialist commercial electrical contractor.
While we are not going explore in-depth the methods of evaluating 3-phase supply, some knowledge is useful to the home inspector.
As discussed in the section about service drops, 3-phase supplies have three hot or ungrounded conductors, and a neutral or grounded conductor. Each of these phases, or legs, carries 120 volts at a dierent phase from the others.
How and from where power is taken in these phased supplies produces dierent types of supply current. The common services include 120, 240, 208 and 480 volts.
In all 3-phase panels, the conductors are color-coded to identify the phase that they are attached to using black, red and blue. While there is no required standard of color coding demanded in the NEC®, the code does tell us that on a 120/208 Delta High-Leg system, the center “B” leg (208V to ground) should be marked with orange tape or other means to identify it as the “high leg.”
These legs can supply 120 or 240 volts, as one would see in a standard 120/240-volt residential supply. So, it is possible for the average inspector to evaluate some electrical branch circuits in oces or other non-industrial settings. But beware of evaluating the distribution panels themselves.
Remember: When in doubt, defer to a licensed electrical contractor!
How to Perform Residential Electrical Inspections 68
The Weird and the Wonderful!
The inspector will occasionally see some very unusual panels in the home. Some are now obsolete. Some are just plain dangerous.
A hundred-plus years ago when we started wiring homes for electricity, there were no standards for panel enclosures. In fact, if an early panel had any kind of enclosure, it was probably built on site from timber and may have had an asbestos liner.
Even today, some homeowners will build a distribution center without the bene!t and protection of a listed enclosure.
Fused Neutral Panels
For a period in the 1920s, fused neutral circuits were very common. They were outlawed in 1928 by the NEC®.
The problem with these is that if the neutral — rather than the live — fuse blows, then the circuit will appear not to be live. However, someone working on the system would easily be able to complete the circuit to the source, providing a return path for the current, and thus be electrocuted.
As discussed, wood enclosures were very common at one time, but other materials have also been used. In particular, Bakelite and other plastics have been used for panel enclosures since the 1940s. They never achieved signi!cant market share, but the inspector may see them, on occasion.
While plastic panels are rare in residential use, they are very common in automotive and marine applications.
1. Fused main disconnects are usually a maximum of _____.
30 amps 60 amps 100 amps 150 amps 200 amps
2. Screw-in fuses are more properly called ___________.
Edison-base fuses Westinghouse fuses Tessler-type fuses
3. Upgrading to ___ fuses stops over-fusing.
A F P S
4. Which of the following statements is true about 240-volt breakers?
240-volt breakers should always be located at the very top of the panel. 240-volt breakers are connected to two separate bus bars in the panel. 240-volt breakers are always 15- or 30- amp.
240-volt breakers draw power from one bus bar.
5. GFCI breakers have _____ conductors.
no one two three
6. T/F: The inspector will !nd overheating only with Zinsco and FPE breakers.
How to Perform Residential Electrical Inspections 70 7. AFCI breakers made by ________ were subject to a recall notice.
Federal Pacific Challenger
8. Zinsco electrical panels are sometimes branded as _________.
Federal Pacific Sylvania
9. Electric panel buses colored red, blue and black are indicative of a ________.
120/240-volt panel 120-volt-only supply
10. Zinsco electrical panels are problematic due to ____________.
not enough amperage for modern needs difficulty obtaining replacement breakers poor connections to the bus
11. Fused neutral circuits were common in the ________.
1890s 1900s 1910s 1920s
Answer Key is on page 108.
Electrical Distribution 71
Electrical Distribution Wiring Types
Wire types for North American wiring practices are de!ned by standards issued by the Underwriters Laboratories, the Canadian Standards Association, the American Society for Testing and Materials, the National Electrical Manufacturers Association, and the Insulated Cable Engineers Association.
Most circuits in modern North American homes and light commercial construction are wired with non-metallic (NM) sheathed cable, often referred to by the brand name Romex®. This type of cable is the least expensive for a given size and is appropriate for dry indoor applications.
As discussed above, we are dealing with:
• copper: Absolutely the best conductor in common use, copper has low electrical impedance, so a relatively small conductor can deliver a lot of power over long distances without too much power loss or heat generation.
• tinned copper: Still sometimes seen at older properties, copper is tinned for two reasons: to aid soldering; and to stop the copper from reacting with old rubber insulation. Tinned copper is often mistaken for single-strand aluminum wiring, but it’s given away by its rubber insulation, as well as cut copper ends, which can sometimes be observed upon closer examination. One will never !nd aluminum wiring with anything other than plastic insulation in residential construction.
• aluminum: This is a good conductor of electricity but has higher impedance to the $ow of electrons, which means that larger conductors need to be used for any given amperage. Aluminum was used for residential branch circuit wiring from the mid-1960s to the late 1970s, but it was found to be unreliable. (We’ll explore this later.)
• copper-clad aluminum: Coating aluminum in copper was an attempt to overcome the issue of oxidation of the aluminum conductors that was leading to failures. It did not have the failures
How to Perform Residential Electrical Inspections 72 associated with pure aluminum and is considered safe. However, copper-clad should be sized the
same as normal aluminum.
Knob-and-tube wiring is so named because of the porcelain !ttings used to support and insulate the conductors from the timber components in the home. The knob holds the wire away from rafters and joists, while the tubes are inserted into holes bored though the joists and studs to protect the conductor and its rubber insulation.
Knob-and-tube wiring was the common method used to wire homes in the United States prior to 1930.
Knob-and-tube is a two-wire system having a hot (ungrounded) and a neutral (grounded conductor) only. No separate ground is used, so all receptacles would have been two-prong only.
The home inspector should report any knob-and- tube wiring as in need of further evaluation by an electrical contractor due to the following reasons:
1. The insulation is often very brittle and leaves conductors exposed when disturbed.
2. All circuits are ungrounded, which will not suit many modern electronics, such as computers, televisions and stereos.
3. The conductors are often buried in attic and wall insulation. This is a problem, as they were designed to work in free air.
4. The wire gauge is commonly 14-AWG only, which is not sucient for most modern household needs.
5. It’s very common for knob-and-tube wiring to have been added to over the years, and it may contain many splices outside of approved enclosures. (Originally, joints in knob-and-tube were all spliced, soldered and taped outside of their enclosures.)
Armored Cable (AC)
Conductors protected by a spiral-wound outer metal sheathing have been around since the early part of the 20th century, and they gained wide acceptance in the 1930s, especially after the NEC’s acceptance in the 1932 Code.
Several types of AC cable exist and they are not all the same. The earliest type was introduced by General Electric under their brand name “BX.” Many people still wrongly call all type-AC cables by this name.
Type-AC cables fall into two categories: those with an internal bonding conductor and those without. In many cases, the sheathing itself, or its internal bond, has been used improperly as the grounding conductor, or, even worse, as the neutral conductor.
In 1959, the NEC® required that all type-AC cable include a bonding strip that connects all the individual convolutions. The older BX cable did not have this, and the exterior metal casing was
Electrical Distribution 73 not meant to be an eective fault current path. Since the 1960s, a newer type of AC-cable assembly
came onto the market. The improved MC cable includes a proper grounding conductor.
Exterior Flexible Conduit
This is often seen by the home inspector as the supply conduit to outside installations, such as air- conditioning compressors.
This AC/BX-type conduit has a PVC outer sheathing to render it watertight, which should be marked “UF” for exterior use. (It is not approved for direct burial, however.)
Dierent types of rigid conduit are available for dierent applications, and some are more common that others in some regions. The three primary types used are:
• EMT/thin-wall: this is electrical metal tubing, which can be bent into shape for installation. • RMC/thick-wall: this is threaded rigid metal conduit, where any changes in direction require
• RNC/PVC conduit: often referred to as Schedule 40 or 80 plastic, this gray-colored rigid non- metallic conduit is very common in newer construction, but it should not be confused with white or ivory-colored PVC piping, which is not rated for electrical use.
Non-Metallic (NM) Cable
Many people use the name Romex® when referring to type-NM cable. Romex® is a trademarked name that has come into common usage for referring to plastic-covered wires, but type-NM just means non-metallic and also applies to other cable styles.
The earliest NM cables were, in fact, rubber-insulated copper conductors bound together as an assembly, with a woven-cloth sheathing. Originally approved by the NEC® in 1928 as replacement for knob-and-tube wiring, it became the most common residential wiring used from the late 1940s, up to the introduction of modern thermoplastic Romex®-type wiring of the early 1960s.
Prior to 1985, standard NM was rated for 60-degree applications, which was increased to 90 degrees and is now marked NM-B.
In type NM cable, conductor insulation is color-coded for identi!cation, typically one black, one white, and a bare grounding conductor. The National Electrical Code® (NEC®) speci!es that the black conductor represent the hot conductor, with signi!cant voltage to earth ground; the white conductor represent the identi!ed or neutral conductor, near ground potential; and the bare/green conductor, the safety grounding conductor not normally used to carry circuit current.
According to InterNACHI’s Standards of Practice, the home inspector is required to report on any observed single-strand, solid-conductor, aluminum branch-circuit wiring.
How to Perform Residential Electrical Inspections 74
Between approximately 1965 and 1973, single-strand aluminum wiring was sometimes substituted for copper branch-circuit wiring in residential electrical systems due to the sudden escalating price of copper. After a decade of use by homeowners and electricians, inherent weaknesses were discovered in the metal that led to its disuse as a branch wiring material. Although properly
maintained aluminum wiring is acceptable, aluminum will generally become defective faster than copper due to certain qualities inherent in the metal. Neglected connections in outlets, switches and light !xtures containing aluminum wiring become increasingly dangerous over time. Poor connections cause wiring to overheat, creating a potential !re hazard. In addition, the presence of single-strand aluminum wiring may void a home’s insurance policies. Inspectors may instruct their clients to talk with their insurance agent about whether the presence of aluminum wiring in their home is a problem that requires changes to the policy’s language.
Facts and Figures
- On April 28, 1974, two people were killed in a house !re in Hampton Bays, New York. Fire ocials determined that the !re was caused by a faulty aluminum wire connection at an outlet.
- According to the Consumer Product Safety Commission (CPSC), “Homes wired with aluminum wire before 1972 [‘old-technology’ aluminum wire] are 55 times more likely to have one or more connections reach !re-hazard condition than a home wired with copper.” Aluminum as a Metal Aluminum possess certain qualities
that, compared with copper, make it
an undesirable material as an electrical conductor. These qualities all lead to loose connections where !re hazards become likely. These qualities are as follows:
- higher electrical resistance. Aluminum has a high resistance to electrical current $ow, which means that,
given the same amperage, aluminum conductors must be of a larger diameter than would be required by copper conductors.
- less ductile. Aluminum will fatigue and break down more readily than copper when subjected to bending and other forms of abuse because copper is more ductile. Fatigue will cause the wire to break down internally and will increasingly resist electrical current, leading to a buildup of excessive heat.
- galvanic corrosion. In the presence of moisture, aluminum will undergo galvanic corrosion when it comes into contact with certain dissimilar metals.
- oxidation. Exposure to oxygen in the air causes deterioration to the outer surface of the wire. This process is called oxidation. Aluminum wire is more easily oxidized than copper wire, and the compound formed by this process – aluminum oxide – is less conductive than copper oxide.
Electrical Distribution 75 As time passes, oxidation can deteriorate connections and present a !re hazard.
- greater malleability. Aluminum is soft and malleable, meaning it is highly sensitive to compression. After a screw has been over-tightened on aluminum wiring, for instance, the wire will continue to deform or “$ow” even after the tightening has ceased. This deformation will create a loose connection and increase electrical resistance in that location.
- greater thermal expansion and contraction. Even more than copper, aluminum expands and contracts with changes in temperature. Over time, this process will cause connections between the wire and the device to degrade. For this reason, aluminum wires should never be inserted into the “stab,” “bayonet” or “push-in” types of terminations found on the back of many light switches and outlets.
- excessive vibration. Electrical current vibrates as it passes through wiring. This vibration is more extreme in aluminum than it is in copper, and, as time passes, it can cause connections to loosen. Identifying Aluminum Wiring
- Aluminum wires are the color of aluminum and are easily discernible from copper and other metals.
- Since the early 1970s, wiring-device binding terminals for use with aluminum wire have been marked CO/ALR, which stands for copper/aluminum revised.
- Look for the word “aluminum” or the initials “AL” on the plastic wire jacket. Where wiring is visible, such as in the attic or electrical panel, inspectors can look for printed or embossed letters on the plastic wire jacket. Aluminum wire may have the word “aluminum,” or a speci!c brand name, such as Kaiser Aluminum, marked on the wire jacket. Where labels are hard to read, a light can be shined along the length of the wire.
- When was the house built? Homes built or expanded between 1965 and 1973 are more likely to have aluminum wiring than houses built before or after those years. Options for Correction Aluminum wiring should be evaluated by a quali!ed electrician who is experienced in evaluating and correcting aluminum wiring problems. Not all licensed electricians are properly trained to deal with defective aluminum wiring. The CPSC recommends the following two methods for correction of aluminum wiring:
- Rewire the home with copper wire. While this is the most eective method, rewiring is expensive and impractical, in most cases.
- Use COPALUM crimps. This crimp connector repair consists of attaching a piece of copper wire to the existing aluminum wire branch circuit with a specially designed metal sleeve and powered crimping tool. This special connector can be properly installed only with the matching AMP tool. An insulating sleeve is placed around the crimp connector to complete the repair. Although eective, they are expensive (typically around $50 per outlet, switch or light !xture). Although not recommended by the CPSC as methods of permanent repair for defective aluminum wiring, the following methods may be considered: • application of anti-oxidant paste. This method can be used for wires that are multi-stranded or wires that are too large to be eectively crimped. • pig-tailing. This method involves attaching a short piece of copper wire to the aluminum
wire with a twist-on connector. The copper wire is connected to the switch, wall outlet, or other
How to Perform Residential Electrical Inspections 76
termination device. This method is eective only if the connections between the aluminum wires and the copper pigtails are extremely reliable. Pig-tailing with some types of connectors (even though Underwriters Laboratories might currently list them for the application) can lead to increasing the hazard. Also, beware that pig-tailing will increase the number of connections, all of which must be maintained. Aluminum Wiring Repair (AWR), Inc., of Aurora, Colorado, advises that pig-tailing can be useful as a temporary repair or in isolated applications, such as the installation of a ceiling fan.
- CO/ALR connections. According to the CPSC, these devices cannot be used for all parts of the wiring system, such as ceiling-mounted light !xtures or permanently wired appliances. As such, CO/ALR connections cannot constitute a complete repair. Also, according to AWR, these connections often loosen over time.
- AlumiConn®. Although AWR believes this method may be an eective temporary !x, they are wary that it has little history, and that these are larger than copper crimps that are often incorrectly applied.
- Replace certain failure-prone types of devices and connections with others that are more compatible with aluminum wire.
- Remove the ignitable materials from the vicinity of the connections. Aluminum wiring can be a !re hazard due to inherent qualities of the metal. Inspectors should be capable of identifying this type of wiring. Repair Methods Since the early 1970s, several methods have been tried to improve the contact between aluminum wire and junctions and receptacles. The single biggest issue is that it is very dicult for a contractor to know where all of the hidden junction boxes are in an older home. Re-wiring in copper: This is obviously the best choice by far, as it completely replaces the aluminum branch-circuit wiring. However, this is very costly and disruptive. Pig-tailing copper: A method many electricians have tried was to pig-tail a piece of copper wire onto the aluminum using a wire nut. There were even special purple wire nuts produced with antioxidant paste in them designed for this application. This is not considered an eective repair. CO/ALR switches and receptacles: These were designed to replace previous CO/AL receptacles, as they had a higher-quality conductor lug assembly. However, this addresses only the issues of switches and outlets, but not the connections in boxes. This is not considered an eective repair. COPALUM connectors: These are the recommended upgrade for aluminum wiring. A special crimp connector and crimping tool are used to pig-tail a piece of copper wire onto the aluminum conductor. It is then covered with a heat-shrunk insulation. This is the only CPSC-approved repair, but some connections still may be inaccessible.
Electrical Distribution Branch Circuit Connections
One of the !rst things the inspector should evaluate is the size of the conductors relative to the amperage rating of the fuse or breaker. As we have seen, if the breaker is rated for 30 amps but
the conductor is a 14-AWG rated for 15 amps, we are likely to see the conductor overheating and potentially starting a !re. Bear in mind that there may be exceptions under special conditions. For example, the NEC® allows 12-AWG on a 30-amp under 240.4 (E) or (G). A nameplate on an AC unit or a speci!c motor load may indicate such exceptions to the standard rules. (See table to follow.)
The table below shows the most common conductor sizes used in residential branch circuits, along with their maximum permitted breaker or fuse sizes.
Evaluating In-Panel Wiring
The purpose of this section is to look in more detail at the connections themselves inside the panel. We have already discussed the panel conditions and the breaker/fuse issues, but there is still much to inspect.
Probably the most common electrical defect that an inspector will report is “double-tapping” of fuses and breakers, but there are many other connections that may also be incorrect.
|Breaker or Fuse Size||Copper Conductor||Aluminum Conductor||Common Usage|
|15-amp*||#14/2 with ground NM||–||Lighting circuits and typical general-use receptacles in living area. Dishwasher. Disposal. Refrigerator/ freezer.|
|20-amp*||#12/2 with ground NM||–||Receptacle and switches in kitchen, laundry, bathrooms, and dining rooms. Microwave, Dishwasher. Disposal. Refrigerator/freezer. Hydro massage tub.|
How to Perform Residential Electrical Inspections 78
|Breaker or Fuse Size||Copper Conductor||Aluminum Conductor||Common Usage|
|30-amp*||#10/3 with ground NM||–||Water heater. Clothes dryer. Condensing unit.|
|40-amp*||#8/3 with ground NM||6/6/6/6 AL SER||Oven. Cooktop. Range.|
|50-amp||#6/3 with ground NM||4/4/4/6 AL SER||Oven. Cooktop. Range.|
|100-amp||3 AWG||1 AWG||Remote distribution panel|
|100-amp**||4 AWG**||2 AWG**||SE cable|
|150-amp**||1 AWG**||2/0 AWG**||SE cable|
|200-amp**||2/0 AWG**||4/0 AWG**||SE cable|
* Aluminum single-strand wiring should always be deferred to a licensed electrical contractor for inspection. A 40-amp size is the minimum, according to the 2017 NEC® 210.19(A)(3). A minimum rating of 40 amperes is required for any range rated 8.75 kVA or more. Typically, 50- and 60-ampere circuits are installed for ranges. Refer to 2021 IRC E3702.9.1, Minimum Branch Circuit for Ranges.
** Based on NEC® 310.15(B)(6) and 2015 IRC E3702.9.1.
Double-tapping is sometimes also called “double taps” or “double-lugging.” This is when there are two conductors
terminating under a screw or lug that is rated for only
one. The problem here is that each conductor will not have enough contact area against the screw or its lug, which may lead to arcing and overheating of the conductors.
These should always be fully evaluated, as there are a couple of exceptions:
• breakers rated for two conductors (made by Cutler-Hammer and Square D); and
• conductors spliced together and pig-tailed into a breaker or fuse.
Electrical Distribution 79
As the neutral is also a current-carrying conductor, the neutrals should each be terminated separately on the neutral bus.
An inspector will often !nd signs of arcing and overheating where any multiple conductors share a common lug.
This condition is basically just another double-tapping situation.
The inspector will often see homeowner wiring using things like doorbell or speaker wire, and cut-down extension cords supplying circuits derived from the panel.
This is always unacceptable and should be replaced by a licensed electrical contractor.
Any conductor that has been nicked as the insulation was removed is now of a smaller diameter than intended and has a higher resistance to the $ow of electrons.
This higher impedance is just the same as having too small a conductor on the circuit, since the damaged area will be the weak link and may either act as the fuse or overheat.
This grayish paste is commonly found on older aluminum multi-strand conductors and is still required by some municipal electrical inspectors. This paste was designed to stop the aluminum from oxidizing, and thus be better able to maintain a clean contact footprint in its lug.
Interestingly, the NEC® has never required its use—rather, they have “permitted” it. The alloys used in aluminum wire have greatly improved since the early 1980s, and while many manufacturers used to recommend its use on their conductors,
few do so now.
All abandoned wiring should be removed from the electrical panel, or, at the very least, it should be properly isolated so that the conductors are not able to make contact with any live components.
How to Perform Residential Electrical Inspections 80 Arcing and Overheating
As we have seen, any of the conditions covered may cause overheating to the conductors.
The inspector should recommend further evaluation of any wiring that is in any way de!cient, as failures can and do lead to !res, which can lead to loss of life.
Splices in Panels
While electrical splices in panels are not in and of themselves improper, the home inspector should bear in mind that, like double taps, they are the line of least resistance and often done by unquali!ed persons.
Generally untidy panel wiring, double-taps, lots of splices, and wire nuts are indicative of homeowner wiring, which probably requires further evaluation.
Occasionally, the inspector will open a panel and see most or all of the neutral conductors fried. This may have been caused by the property having been struck by lightning. The neutrals will be most aected by
this, since they are, of course, connected to the grounding system.
Protection of Wiring
Electrical Distribution 81
All current-carrying wiring needs some form of protection from mechanical damage. Also, the occupants of the home need protection from potential shocks where wires are spliced together.
Obviously, there should be no exposed wiring in the !nished or livable areas of the home, but this means that some un!nished areas may have exposed, non-metallic Romex®-type cables. In this section, we’ll look at those areas and discuss what is and is not acceptable.
The guidelines in this section are based on current adopted NEC® codes and may not be applicable in your area, or may not apply to an older property. Remember: Code is based on previous failures that have produced unsafe conditions.
The home inspector should report any exposed wiring at the exterior, especially interior-type wiring, such as Romex® types, which are not rated for exposure to ultraviolet light (sunlight). Also, any exterior conductors should be protected against mechanical damage to a height of 8 feet.
Crawlspace and Basement Wiring
In most jurisdictions, exposed wiring is allowed in basements and crawlspaces. In the northern U.S., we commonly see non-metallic cables unprotected as they leave the panel, and the circuits generally run unprotected on the ceiling joists.
Crawlspaces are the same unless a prohibitive condition exists, such as a very damp area; then, exposed cable assemblies are the norm.
According to the 2008 NEC®, crawlspaces and un!nished basements that have NM cable installed shall be drilled through the joists unless installed on a running board. Cables with three 8-AWG
or two 6-AWG and larger shall be allowed on the surface of the joists.
How to Perform Residential Electrical Inspections 82
Although exposed conductors are allowed to run in attics, there are some safety concerns that the home inspector needs to be aware of, especially as the homeowner is going to enter the attic space to store seasonal goods, etc.
All conductors should be protected within 6 feet of the scuttle opening. This means that no cables should be run on top of joists in this area. This dimension also includes the underside of roof framing rafters. If they run perpendicular to the joist, they should either be drilled through the timbers and have a running board over the top, or be stapled to the side of a running board.
Wiring in Cabinetry
The home inspector will often see unprotected wiring in under-sink locations, especially supplying waste disposals. If any hard-wired appliances have exposed conductors, they should be protected with metal spiral armoring.
Protection of Wiring Through Studs
In frame construction, all of the home’s conductors must be run through the wall stud work to supply the outlets. These hidden conductors need to be protected from accidental damage.
Most frame homes are built with either timber or steel studs, and each has separate protection requirements:
• Timber studs: Any cable assemblies closer than 1 inches from the from the front and back faces of the stud need to be protected from damage from drywall screws, and the homeowner hanging pictures, etc. This is achieved by installing a nailing plate on the stud. Note that the 1 inches applies to both sides of the stud if the required distance is not maintained.
• Steel studs: Where NM cable or electrical non-metallic tubing is run through openings in steel studs, protection against penetration is required. A steel sleeve, steel plate, or steel clip not less than 1/16-inch thick shall be used to protect the cable or tubing. An opening in the stud requires a plastic bushing to protect the cable or tubing from cha!ng against the steel’s raw edge. This protection must encircle the entire opening, and not just the bottom half.
Support of Cables and Conduits
All cables, cable assemblies, and conduits need regular support from the structure. The home inspector will often see great lengths of Romex® and other conductor types strung unsupported through crawlspaces and attics. This, again, is indicative of homeowner work and needs correcting.
The basic speci!cations for supports are outlined below:
• NM/Romex® cables: stapled within 12 inches of metal enclosures (and 8 inches from plastic
Electrical Distribution 83 gang boxes), and every 4 feet and 6 inches of run length.
• AC cables: stapled within 12 inches of metal enclosures, and every 4 feet and 6 inches of run length. MC cable has a run-length that is extended to 6 feet between the required supports.
• Metal conduit/EMT: clamped within 36 inches of enclosures, and every 10 feet of run length.
Protection of Personnel
Exposed wiring, and especially exposed splices and connections, are obviously a danger to the home’s occupants.
All connections in conductors need to be made in approved enclosures, typically panelboards, junction or J-boxes, and gang boxes (a gang box is what is behind switches and receptacles).
The home inspector should report any splices or other connections that can be seen either outside of enclosures, or in enclosures where the cover plate is missing.
All enclosures and J-boxes should also have proper cable connectors where the conductors enter the box. (Plastic gang boxes do not require these, since strain relief is built in.)
1 for using a receptacle to meet the lighting outlet requirement in rooms other than bathrooms and kitchens. It will not meet the 210.52(A)(1) wall spacing requirements.
In this section, we will look at the current standards for outlets around the home, and the methods for testing them.
Many older homes, however, will not have what would now be the required number of outlets. This would not necessarily be a defect, but the home inspector would be well-advised to point out to the homeowner (or home buyer) that there may not be enough outlets to suit a modern family’s needs.
Homes with many appliances connected through extension cords are typical of properties built with insucient outlets.
The term “receptacles” actually covers all types of applications, whether they are light !xtures or wall outlets. Every habitable space in the home is required to meet minimum standards of power and lighting availability. Never install a switch receptacle fully inside of a room where both the top and bottom of the duplex is controlled by a switch. A switched receptacle may be acceptable to meet the 210.70(A)(1) Exception
How to Perform Residential Electrical Inspections 84
All habitable spaces are required to have electrical power and, in new construction, one would expect to see an outlet at every 12 feet of wall space. Even hallways longer than 10 feet are required to have power.
Standard wall-type receptacles pose a danger when mounted horizontally in a $oor structure.
Dirt, dust, and any spilled water will aect the outlet, plus children or pets will always play with anything on the $oor.
Recommend upgrading $oor receptacles to the approved type, with special covers.
Any un!nished space that houses serviceable equipment, such as furnaces and air handlers, is required to have not only a light but also a power outlet. This includes attics and crawlspaces.
All kitchens are now required to be supplied by at least two 20-amp circuits over and above any requirements for dedicated outlets for stoves, etc. These circuits shall not serve any lighting needs.
One of these branch circuits should be used for small appliance receptacles no more than 20 inches above the countertop. These outlets must also be GFCI-protected. The minimum two 20-amp circuits shall both supply receptacles serving the countertop space.
As of the 2002 NEC®, all kitchen receptacles installed in new construction are required to be GFCI- protected.
All counter spaces wider than 12 inches should have an outlet, and the maximum distance between outlets should be no more than 4 feet. There should also be a receptacle within 2 feet of each end of the counter ends, and from any break in the countertop (such as for a range, refrigerator and sink).
Islands and peninsulas are also required to have at least one receptacle to serve the countertop space. If the space is not available on the countertop area, the NEC® allows the receptacle to be installed below the countertop’s surface, which must not be more than 12 inches below the countertop, and not installed under any overhang 6 inches or more from the base of the island or peninsula to the edge of the overhang. No countertop outlets are allowed to be installed face-up in the horizontal surface.
When dealing with the space behind a corner-mounted sink or counter-mounted cooking unit, the 2008 NEC® requires that if such space is less than 18 inches, it is not considered a wall space. If
that space is 18 inches or more, it must meet the same spacing requirements previously discussed. A countertop with an extended face sink or a counter-mounted cooking unit (such as when that
counter sticks out and creates a space behind the sink or cooking unit) is not considered counter space if that space is less than 12 inches. If that space is 12 inches or more, then it must meet the same spacing requirements previously discussed.
When dealing with islands and peninsula, the 2008 NEC® requires that where a range, counter- mounted cooking unit, or sink is installed in an island or peninsular countertop, and the width of the countertop behind the range, counter-mounted cooking unit, or sink is less than 12 inches, the range, counter-mounted cooking unit, or sink is considered to divide the countertop space into two
Electrical Distribution 85 separate countertop spaces. This means that both sides would need a receptacle to meet current
Most jurisdictions require dishwashers and waste disposals to be on dedicated circuits. Refrigerators are typically plugged into dedicated outlets, and this is allowed by the NEC®.
There must be a minimum of one 20-amp circuit within 6 feet of the appliance location. Dryer outlets will be covered in the 240-volt section, but they should have a 4-wire, 30-amp minimum supply.
Garages were required to have a minimum of one GFCI outlet, and inspectors may !nd that
they also have non-GFCI receptacles dedicated to appliances, such as door openers and extra refrigerators and freezers. Lighting is also required. However, be aware that under the 2008 NEC®, the exceptions that allow dedicated receptacles for speci!c appliances were removed. Now, all receptacles in garages and un!nished basements must be GFCI-protected, including sump pumps. The only exceptions are for !re alarm and burglar alarm systems, and receptacles outside that are installed for roof snow-melting equipment.
In the bathrooms of newer homes, outlets are required to be on dedicated 20-amp, GFCI-protected circuits, and at least one receptacle is required to be installed within 3 feet of any vanity basin.
The home inspector is justi!ed in suggesting that non-GFCI receptacles in older bathrooms be upgraded for safety reasons.
There is also a common misconception that no switches or receptacles may be installed within 3 feet of a bath or shower enclosure. This is correct for Canada, but not a requirement in the United States.
Newer homes are required to have a
minimum of one outlet at the front and another at the rear of the outside of the home. These receptacles are required to be weathertight while in use, and GFCI-protected.
Recommend upgrading of older receptacles, as this is a safety enhancement that should be considered.
How to Perform Residential Electrical Inspections 86 Non-GFCI outlets are allowed for dedicated single outlets only, such as one will !nd supplying
heater strips in colder climates.
The inspector should visually inspect all receptacle outlets and report the following:
• 2-wire-only circuits;
• damaged or missing cover plates;
• missing screws;
• damaged receptacles;
• signs of overheating on receptacles or surrounding walls; and/or • lack of GFCIs where speci!ed in 210.9 of the 2008 NEC®.
Branch Circuit Outlet Testing
InterNACHI’s Standards of Practice requires that the inspector inspect a “representative” number of receptacles, including those deemed to be GFCI- and AFCI- protected.
It’s a good idea to check every receptacle that can be physically accessed that does not have something plugged into it, as well as every
The functionality of some common testers can indicate:
• open ground;
• open neutral;
• open hot;
• hot/ground reversed; • hot/neutral reversed; • normal;
• GFCI trip;
• bad (high-resistance) ground; • AFCIs for proper operation; • GFCIs for proper operation; • shared neutrals; and
• correct wiring.
There are many dierent types of circuit testers available, starting with very basic continuity testers, which cost a few dollars, up to full-function testers, which cost several hundred dollars.
The dierences between the various
models are what they are able to test for and how they display the results.
It is good practice for an inspector to have and use a receptacle tester with a GFCI and AFCI test button.
Electrical Distribution 87
GFCI- or AFCI-protected circuit.
Before exploring these protocols, we must understand how receptacles are be correctly wired. A receptacle has the following characteristics:
• the small slot is the hot or ungrounded supply;
• the large slot is the neutral or grounded return; and • the round pinhole is the grounding conductor.
This is very important if the receptacle has reversed polarity (hot and neutral switched) because things like lamp-holder collars may become live and pose an electrocution hazard.
It is very common to !nd 3-prong receptacles with no ground, or, worse, receptacles with a false or bootleg ground where the grounding terminal has been illegally connected to the neutral.
How to Perform Residential Electrical Inspections 88
Sometimes referred to as “bootleg” grounds, false grounds occur when the grounding terminal on the receptacle has been improperly connected to the neutral.
Most testers will not be able to read this condition, as the grounds and neutrals are correctly terminated together at the panel anyway.
The inspector should be suspicious of older-style wiring in the panel that tests like a grounded circuit at the receptacles. It is very common to !nd an older home with 2-wire conductors upgraded to 3-prong outlets, but where the ground has been “faked.” This can lead to very dangerous conditions downstream of the receptacle with the illegal connection, especially if there’s a wiring or appliance failure.
Some inspectors check voltage drop along conductors. This falls well outside of industry standards of practice, but with electrical components becoming increasingly more sensitive to voltage $uctuations, more inspectors have started to check for this.
Voltage drop can also be indicative of too many outlets on a circuit, poor connections, or undersized conductors on long wiring runs, all of which could lead to overheating and failures.
The National Electrical Code® recommends that voltage should not drop more than 3% on branch circuits, and a 5% overall drop, including the service itself.
Ungrounded Two-Prong Receptacles
Two-prong receptacles are often found in older homes and are connected to 2-wire cables that do not have ground wires, which are intended to protect people and electrical devices in case of a fault. It is possible to retro!t a new 3-prong or GFCI receptacle into the same receptacle box without any rewiring, as long as the box itself is grounded.
Metal boxes attached to armored or BX cable, which is a type of wiring commonly found in older homes, are typically found to be properly grounded. The armored or BX cable’s $exible metal jacket serves the same purpose as a dedicated ground wire. If the box is not grounded, a GFCI can be installed, or an electrician can be hired to !x the wiring.
Simply replacing an older 2-prong outlet with a 3-prong outlet can be hazardous because the receptacle will appear to be functional with a ground, but, in fact, there isn’t one. If someone were to plug a faulty 3-prong device into that “fake” grounded receptacle, a shock hazard is very likely. Electricity moving through the device casing would create an energized surface from which a person could be electrocuted.
Another problem with replacing ungrounded 2-prong receptacles with 3-prong ones is related to surge-protection devices, which rely on a solid ground to route any transient activity. The ungrounded receptacle would not be able to protect the device from a surge.
It is permissible to replace a 2-prong ungrounded outlet with a 3-prong GFCI outlet, but it must be labeled “GFCI-Protected Outlet, No Equipment Ground.” Even though there is not a grounding conductor, there is still some protection against shock provided by the GFCI.
If an inspector has doubt as to what is being inspected, a quali!ed electrician should be consulted.
Electrical Distribution 89
The home inspector should check the following conditions on a representative number of receptacles:
• no power present;
• no ground;
• open neutral;
• reversed polarity (hot and neutral); and • reversed ground and hot.
The inspector may also choose to invest in equipment to enable him to report on:
• low-resistance grounds; • bootleg grounds;
• true voltage; and
• voltage drop.
240-Volt Terminations 3-Wire Appliances
Prior to the adoption of the 1996 NEC® code revisions, 3-wire, 240-volt supplies were common. The cable assembly carries:
• two 120-volt ungrounded (hot) conductors; and • one grounded (neutral) conductor.
As there is no separate grounding means in this installation, the metal frame of the appliance was allowed to be bonded to the neutral. This is no longer allowed in new construction.
Since adoption of the 1996 NEC®, all 240V circuits are required to be 4-conductor assemblies carrying:
• two 120V ungrounded (hot) conductors; • one grounded (neutral) conductor; and • one equipment grounding conductor.
Some appliances still have the bond between the cabinet and the neutral, and this needs to be removed when used on a 4-wire circuit.
If a 3-wire con!guration exists and one wishes to extend the circuit (for example, in a renovation), it would be considered a new installation and must be re-wired in a cable with four conductors.
How to Perform Residential Electrical Inspections 90 Receptacle Blade Patterns
There are many odd receptacle styles out there, but the two that are most common around the home are:
- dryer receptacle: A 240V clothes dryer receptacle has four prongs. The top prong is round and is for the ground connection. The bottom prong is L-shaped and is for the neutral wire. The two vertical slots on the sides are for the two hot wires.
- stove receptacle: A 240V oven receptacle also has four prongs, but the neutral prong is straight and not L-shaped. It is, however, narrower and thicker than the hot-wire prongs. These two plugs have four prongs because they use two hot wires to provide the 240-volt power. These receptacles have dierent designs so that a 30-amp dryer cannot be accidentally connected to a 50-amp stove circuit, for example. GFCI Circuits
Ground-Fault Circuit Interrupters Since the early 1970s, GFCIs have been required in an increasing number of damp and wet locations and, more recently, this requirement has extended to all receptacles in garages. Because they are safety devices, the home inspector should check every installed GFCI circuit and may advise the client of areas where they should also be !tted. History of GFCIs Charles Dalziel (1904-1986), a professor of electrical engineering at the University of California, invented the ground-fault circuit interrupter (GFCI) in 1961. He came to realize that a common cause of deaths was the result of ordinary household circuits malfunctioning in the ground fault. His research objective then became to create a device that would interrupt a ground-fault current before it became large enough to cause human physiological damage. The sensitivity, speed of action, reliability, small size, and cost required made the device almost impossible to design. However, in 1965, Dalziel received a patent for a “ground-fault current interrupter” that would interrupt current before it grew to 0.005 of an ampere, and which was small, reliable and inexpensive. The device was based on a magnetic circuit, plus a then-newly developed semiconductor device. Most of the time, his invention does nothing; it just monitors the dierence in the current $owing into and out of a tool or appliance. But when that dierence exceeds 5 milliamps (nominal) — an indication that a ground fault may be occurring — the GFCI shuts o the $ow in as little as 0.025 of a second.
Electrical Distribution 91
How Does a GFCI Work?
GFCIs are designed to sense any dierence in voltage between the supply on the ungrounded (hot) conductor in a circuit and the grounded (neutral) conductor.
If the circuitry recognizes a dierential of more than 5 milliamps (nominal) between supply and return, a solenoid trips open the circuit, causing all power to be disconnected.
For this reason, a GFCI breaker (or a correctly wired GFCI receptacle) can protect all receptacles farther downstream.
The image above shows correct wiring to protect downstream outlets.
Types of GFCI Devices
There are four basic types of GFCIs in common usage, and two or three of them are common in residential construction. They are:
1. GFCI breakers in the distribution panel;
2. GFCI receptacles at in-home locations;
3. stand-alone GFCIs, as sometimes used with pools; and
4. extension cords with built-in protection, primarily found on construction sites.
GFCI on 2-Wire Circuits
There is a common misconception that GFCIs work only on grounded circuits. This is not entirely the case. While there are conditions under which the GFCI will not be able to trip without a ground, the inspector should still recommend that any circuits in potentially wet or damp locations be !tted with them as a safety precaution.
How to Perform Residential Electrical Inspections 92 GFCI Requirements
To protect people, ground-fault circuit interrupter (GFCI) protection should be installed in all bathrooms with 125-volt, single-phase, 15- and 20-ampere receptacles. A bathroom is not necessarily a room. It is an area that includes a lavatory (wash basin) and a water closet (toilet), a tub, or a shower. There are no exceptions for the GFCI requirement in bathrooms. All bathroom receptacles would include, for example, a receptacle in a light !xture, a receptacle for a clothes washer, or a receptacle for any appliance installed in a bathroom.
Bathtub and Shower Stall Receptacles
All 125-volt, single phase, 15- and 20-ampere receptacles located within 6 feet of the outside edge of a bathtub or shower stall must have GFCI protection. There is a standard that prohibits receptacles installed within bathtub and shower spaces, but they are permitted to be located outside of those spaces.
To protect people, ground-fault circuit interrupter (GFCI) protection should be installed in laundry rooms with 125-volt, single-phase, 15- and 20-ampere receptacles.
Garage and Accessory Buildings
To protect people, GFCI protection should be installed at all 125-volt, single-phase, 15- or 20-ampere receptacles installed in garages and grade-level portions of un!nished accessory buildings used for storage or work areas.
Even a storage shed must have GFCI protection. Where an appliance (food freezer or refrigerator) is plugged into a receptacle in the garage, that receptacle must be GFCI-protected. In the past, there was an exception for an appliance that caused nuisance tripping of the GFCI, but this exception is no longer allowed.
There must be at least one receptacle outlet installed outside at the front and back of the house that has direct access to the ground surface, and those receptacles must be readily accessible from the ground surface and not located higher than 6 feet, 6 inches above the ground surface.
To protect people, GFCI protection must be installed at all 125-volt, single-phase, 15- and 20-ampere receptacles installed outdoors.
The exception for GFCI protection is for outdoor receptacles that are not readily accessible and are used for temporary/non-permanently installed snow-melting equipment powered using a dedicated circuit.
A receptacle installed outdoors should have an enclosure for the receptacle that is weatherproof when the receptacle cover is closed and an attachment plug is not inserted.
Outdoor Deck Outlet
Balconies, decks, and porches that are accessible from the inside of the house are required to have at least one receptacle outlet installed within the perimeter of the balcony, deck, or porch. This
Electrical Distribution 93
receptacle must be located higher than 6 feet, 6 inches above the surface of the balcony, deck, or porch. All outdoor receptacles, including those at the balcony, deck, or porch are required to be GFCI-protected.
To protect people, GFCI protection should be stalled at all 125-volt, single-phase, 15- and 20-ampere receptacles in the crawlspace when such place is at or below grade level. The 120-volt lighting outlets located in the crawlspace should be GFCI-protected, too. If there is a receptacle in the crawlspace, it must be GFCI-protected.
To protect people, GFCI protection should be installed at all 125-volt, single-phase, 15- and 20-ampere receptacles installed in un!nished basements. Un!nished basements are de!ned as portions or areas of the basement not intended as habitable rooms such as storage and work areas. The exception would be a receptacle supplying only a permanently installed !re alarm or burglar
To protect people, GFCI protection should be installed at all 125-volt, single-phase, 15- and 20-ampere receptacles that serve countertop surfaces. Any countertop receptacle, even in an area far
away from the kitchen sink, is required to be GFCI-protected.
Kitchen Dishwasher Branch Circuit
GFCI protection must be provided to outlets that supply dishwashers, whether the appliance is hard-wired or cord-and-plug-connected. A GFCI-type circuit breaker or a GFCI receptacle device can be used. It’s common to !nd a single (not duplex) receptacle for the dishwasher mounted in the back of an adjacent kitchen sink base cabinet.
Indoor Damp and Wet Locations
Receptacles installed in indoor damp and wet locations must be GFCI-protected.
To protect people, GFCI protection should be installed at all 125-volt, single-phase, 15- and 20-ampere receptacles that are located within 6 feet of the outside edge of a sink that is located in
an area other than a kitchen. Receptacle outlets shall not be installed in a face-up position in the counter top or work surface.
To protect people, GFCI protection should be installed at all 125-volt, single-phase, 15- or 20-ampere receptacles installed in boathouses.
To protect people, GFCI protection should be installed for outlets supplying up to 240 volts at boat hoists.
How to Perform Residential Electrical Inspections 94 Electrically Heated Floors
To protect people, GFCI protection should be installed at electrically heated $oors in bathrooms, kitchens and in hydro-massage bathtub, spa and hot tub locations.
GFCIs should be installed in readily accessible locations.
Testing GFCI Circuits
Many common circuit testers will not be able to trip a GFCI installed on a 2-wire circuit, as most testers actually trip a GFCI by creating a partial fault to ground. Obviously, if there is no ground to energize, then the neutral will not be able to sense any voltage drop.
The manufacturers state that their equipment be tested by using the test and reset buttons on the breaker or receptacle. However, many inspectors usually check them with their receptacle tester functions. The most sophisticated testers check not only that they trip, but also measure at what voltage they trip. However, the only proper way to test a GFCI is using the button on the breaker or receptacle itself.
Equipment grounding is not necessary for a GFCI to function properly. The grounded person becomes the equipment grounding conductor, and the current going through him creates the imbalance that trips the GFCI. This is why GFCIs are allowed to replace open-ground receptacles without adding an equipment grounding conductor.
Any breaker or receptacle that fails to trip and reset properly should be written up as in need of urgent replacement.
Remember: Industry standards dictate that ALL accessible GFCI receptacles be tested.
AFCI: Arc Fault Circuit Interrupter History of AFCIs
AFCIs were developed in response to a need for equipment to sense when an arc fault was occurring. AFCIs were !rst mentioned in the 1999 revision of the NEC®. It required that bedroom receptacles were to be protected by AFCI breakers.
Studies of building !res had attributed many electrical faults to an arcing type, which were igniting $ammable materials within the building structure.
The Consumer Product Safety Commission (CPSC) asked the electrical industry to look at a technical solution to the issue of preventing !res by tripping circuits that were exhibiting power $uctuations due to arc faults.
AFCIs are able to detect faults as low as 5 amps (peak) for series arcs, and 75 amps (peak) for parallel arcs. They can also detect arcing caused by faults, such as dead-shorts due to nails and screws through conductors, and arcing due to loose connections anywhere in the circuit.
Electrical Distribution 95
AFCI and GFCI Protection
A combination-type arc-fault circuit interrupter should be installed to provide protection at all branch circuits that supply 120-volt, single-phase, 15- and 20-ampere outlets installed in family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreations rooms, closets, hallways, and similar rooms or areas.
Where branch-circuit wiring is modi!ed, replaced, or extended, the branch circuit should be protected. Please refer to Section E3902 of the 2015 IRC that relates to GFCIs and AFCIs.
GFCI protection is recommended for the following:
- 15- and 20-amp kitchen countertop receptacles and outlets for dishwashers;
- 15- and 20-amp bathroom and laundry receptacles;
- 15- and 20-amp receptacles within 6 feet of the outside edge of a sink, bathtub or shower;
- electrically-heated $oors in bathrooms, kitchens, and hydromassage tubs, spas, and hot tubs;
- 15- and 20-amp exterior receptacles, which must have GFCI protection, except for receptacles not readily accessible that are used for temporary snow-melting equipment and are on a dedicated circuit;
- 15- and 20-amp receptacles in garages and un!nished storage buildings;
- 15- and 20-amp receptacles in boathouses and 240-volt and less outlets at boat hoists;
- 15- and 20-amp receptacles in un!nished basements, except receptacles for !re or burglar alarms;
- 15- and 20-amp receptacles in crawlspaces at or below ground level; and
- 15- and 20-amp receptacles in indoor damp and wet locations. GFCIs and AFCIs must be installed in readily accessible locations because they have test buttons that should be pushed periodically. Manufacturers recommend that homeowners and inspectors test or cycle the breakers and receptacles periodically to help ensure that the electrical components are working properly. AFCI protection is recommended at 15- and 20-amp outlets on branch circuits for bedrooms, closets, dens, dining rooms, family rooms, hallways, kitchens, laundry areas, libraries, living rooms, parlors, recreation rooms, and sun rooms. Similar rooms or areas must be protected by any of the following: • a combination-type AFCI installed for the entire branch circuit. The 2005 NEC required combination-type AFCIs, but before January 1, 2008, branch/feeder-type AFCIs were used.
- a branch/feeder-type AFCI breaker installed at the panel in combination with an AFCI receptacle at the !rst outlet box on the circuit.
- a listed supplemental arc-protection circuit breaker (which are no longer manufactured) installed at the panel in combination with an AFCI receptacle installed at the !rst outlet, where all of the following conditions are met: ° the wiring is continuous between the breaker and AFCI outlet;
° the maximum length of the wiring is not greater than 50 feet for 14-gauge wire, and 70 feet for 12-gauge wire; and
° the !rst outlet box is marked as being the !rst outlet.
How to Perform Residential Electrical Inspections 96 • a listed AFCI receptacle installed at the !rst outlet on the circuit in combination with a listed
overcurrent-protection device, where all of the following conditions are met:
° the wiring is continuous between the device and receptacle;
° the maximum length of the wiring is not greater than 50 feet for 14-gauge wire and 70 feet for 12-gauge wire;
° the !rst outlet is marked as being the !rst outlet; and
° the combination of the overcurrent-protection device and AFCI receptacle are identi!ed as
meeting the requirements for a combination-type AFCI. • an AFCI receptacle and steel wiring method.
• an AFCI receptacle and concrete encasement.
Like many new technologies, the introduction of AFCIs was not trouble-free. In particular, Square D was forced to recall 700,000 breakers due to faults. These breakers were manufactured with a blue test button.
As there are still many of these out there that have not been replaced, the home inspector should pay special attention to blue-button Square D breakers, and advise the client that they may be subject to recall.
When testing AFCIs, as when testing GFCIs, it is recommended by the manufacturers to use the test function on the breaker. However, this only tests the internal circuit board, rather than emulates any actual fault.
Many inspectors are now purchasing specialist testers that simulate an arc fault within the tester.
Home inspectors generally purchase both AFCI and GFCI branch circuit testers. They are as common and easy to use as a $ashlight.
Electrical Distribution 97
All habitable spaces are required to have a source of light. What is less commonly understood is that any area used for storage must also be lit, and any area that houses mechanical equipment must have illumination, too.
All habitable, storage and mechanical locations require light. However, some require a !xed-wall or ceiling light, while others may have just a switched-lighting circuit to control table lamps, etc.
The inspector should also be aware of the concept of the “lit path.” One should be able to walk into any home in the dark and be able to go from one room to the next in a lighted path, switching each light o behind as s/he leaves the hall or room. This is for obvious safety reasons, and, as home inspectors are normally inspecting homes in the daylight, checking for safe light is often forgotten.
Many locations are required to have !xed luminaires (lights). These include:
• storage spaces; and • at exterior doors.
These should be a special consideration for the home inspector, as any staircase with six or more risers should have three-way switches at both the top and bottom of the run.
Many people do a lot of head-scratching when trying to !gure out how three-way circuits work. This diagram shows the correct wiring schematic.
In any 3-way circuit, there are two potential supplies (travelers) to the light, with each of them switched.
When both switches are in contact with one of the travelers, the light is on, but when each switch is in contact with only one traveler, then the light
How to Perform Residential Electrical Inspections 98
Switched receptacle circuits are allowed for all other locations, including:
• living rooms;
• dining rooms;
• home oces;
• family rooms;
• bedrooms; and
• crawlspaces with mechanical equipment.
All switches should be evaluated for:
• missing cover plates;
• damaged cover plates;
• missing screws;
• loose installation;
• loose or worn-out contacts; and • any signs of arcing.
There are several potential problems with lighting to check for.
• Bathroom, bathtub and shower areas: No parts of cord-connected luminaires, chain-, cable- or cord-suspended luminaires, lighting track, pendants, or ceiling-suspended (paddle) fans shall be located within a zone measured 3 feet horizontally and 8 feet vertically from the top of the bathtub rim or shower stall threshold.
• Bathroom luminaires: Unless recessed and listed for a damp and/or wet location, no luminaire is allowed to be within 3 feet of the sides, or within 8 feet above any tub or shower enclosure.
• Ceiling fans: Often, we will see a ceiling fan wobbling around on its mount, or doing a
helicopter impression as it $ies around on its axis because it’s been installed on a standard ceiling box. Remember that !xtures under 35 pounds must be mounted to a box rated for fan-support, and !xtures over 35 pounds cannot be supported by the electrical box at all.
Lighting tracks, hanging light !xtures, and ceiling fans are not allowed with the tub or shower space, which is a zone 3 feet horizontal by 8 feet vertical above the threshold of a shower or the rim of a bathtub. Recessed or surface mounted lighting !xtures are allowed in this zone if they are labeled for use in damp locations. If the !xtures might get wet from shower spray, they must be marked for use in a wet location.
A switch must not be installed within a wet location in a tub or shower space, unless it is installed as part of a listed tub or shower assembly. A surface-mounted switch located in a damp or wet location must be enclosed in a weatherproof enclosure. A $ush-mounted switch in a damp or wet location
Electrical Distribution 99 must be equipped with a weatherproof cover.
Cord-connected luminaires, chain-, cable-, or cord-suspended-luminaires, lighting track, pendants, and ceiling-suspended (paddle) fans must not have any parts located within a the tub and shower zone, which is an area measured 3 feet horizontally and 8 feet vertically from the top of a bathtub rim or shower stall threshold. This area is all-encompassing. It includes the space directly over the tub or shower.
Luminaires within the actual outside dimension of the bathtub or shower to a height of 8 feet vertically from the top of the bathtub rim or shower threshold must be marked for damp locations. If the luminaire is subject to the spray of a shower, it must be marked for wet locations.
A receptacle installed within or directly over a bathtub or shower stall is not permitted. That is a defect and safety hazard.
Lights in contact with insulation should be IC-rated. If not, they should have 3 inches of clearance away from insulation and any other combustible surface or material.
Open incandescent lamps or bulbs are a bad idea near storage shelving, as the heat generated can easily start a !re.
• Protected incandescent bulbs should be no closer than 12 inches to the shelf space. • Fluorescent or recessed lights should be no closer than 6 inches to the shelves.
How to Perform Residential Electrical Inspections 100
Quiz #6, Part 1
1. Which of the following would the inspector defer for a specialist’s evaluation?
single-strand aluminum wiring copper-clad aluminum wiring
2. The earliest residential wiring is called _______.
button-and-tube knob-and-sleeve knob-and-tube button-and-sleeve
3. The minimum copper wiring size carrying 120 volts should be ______.
10 AWG 14 AWG 12 AWG 16 AWG 18 AWG
4. A 14-AWG conductor should be connected to a _______ fuse or breaker.
20-amp 25-amp 10-amp 15-amp
5. “Romex” cable that is not actually of the brand Romex® is more properly called _______.
type BX cable type NM cable type AC cable type UL cable
6. Plastic conduit rated for electrical use is ______ in color.
ivory gray white
7. Electric water heaters should be fed with _____ minimum copper conductors.
6-AWG 10-AWG 8-AWG
8. T/F: Several grounded conductors can terminate on the same lug.
depends on circuit amperage
9. T/F: Anti-oxidant paste should be evident on all aluminum conductors.
10. T/F: The inspector should report all in-panel electrical splices as improper.
11. Wiring closer than ____ to the front of a stud requires protection.
1-1/8 inches 1-3/16 inches 1 inches
12. Unprotected attic electrical wiring should not be within _______ of the entrance opening.
3 feet 4 feet 5 feet 6 feet 8 feet
13. T/F: Unsupported cable assemblies are acceptable in crawlspaces only.
14. Are horizontally-mounted face-up countertop receptacles allowed?
Not if within 3 feet of the sink Yes
How to Perform Residential Electrical Inspections 102 15. Bathroom receptacles should be on ______ circuits.
20-amp, AFCI-protected 20-amp, GFCI-protected 15-amp, GFCI-protected 15-amp, AFCI-protected
16. Which of the following is the inspector not required to test for on electrical receptacles?
17. In a false or bootleg grounded receptacle, the ground wire is connected to ____________.
the grounding wire
the ungrounded wire the receptacle box
the grounded conductor
18. On a standard 120-volt outlet, the smaller rectangular slot is the __________.
ungrounded conductor grounding conductor bonding conductor
19. The home inspector is required to test ___________.
all available receptacles
a representative number of receptacles
20. Which is the only approved repair to aluminum wire terminations?
CO/ALR COPALUM CU/ALR CU/AL
Answer Key is on page 108.
Quiz #6, Part 2
1. The 4-wire, 240V circuit was required as of _____.
1966 1976 1986 1996
2. A 4-wire, 240V cable assembly has ________ conductors.
one hot, two neutral, and one ground
two hot, one neutral, and one ground
one hot, one neutral, one ground, and one earth two hot and two neutral
3. Kitchen stove circuits are required to be a minimum of ______.
25 amps 30 amps 40 amps 50 amps
4. Electric clothes dryer circuits are _____.
60-amp 50-amp 40-amp 30-amp
5. GFCIs were !rst required in the _______ NEC® revision.
1963 1967 1971 1973 1975
6. Kitchen counter GFCIs became a requirement with the adoption of the __________ NEC® edition.
1967 1977 1981 1987
How to Perform Residential Electrical Inspections 104 7. Which of the following locations require GFCI protection?
all of these
none of these
8. T/F: GFCI receptacles work on only 3-wire circuits.
9. GFCIs can protect ____________, if properly wired.
all receptacles on the circuit receptacles upstream
10. AFCIs are required to protect _________________ circuits.
bedroom kitchen bathroom
11. Which of the following locations require !xed lighting?
living rooms bedrooms crawlspaces kitchens
12. Staircases with ___ or more risers require a light switch at the top and bottom of the run.
three four five six seven eight
13. Recessed ceiling lights should be rated ____ if installed against insulation.
EC IC GC CC
Answer Key is on page 109.
How to Perform Residential Electrical Inspections 106 Appendix I: Answer Keys
Answer Key for Quiz #1
1. Which of the following should NOT be worn during an inspection? Answer: nylon clothing
2. The following item is safe to insert into an electrical panel: Answer: none of these
3. The electrical panel should not be opened if the following conditions exist: any of these. 4. The correct name for a live wire is an ungrounded conductor.
5. An electrical panel cover is more properly called the dead front.
6. A service panel that does not contain the disconnect is called the distribution panel.
7. Wires to outlets are called branch circuit conductors.
8. Electromotive force is measured in volts.
9. Ohms are a measurement of resistance.
10. Voltage is equal to amps x resistance.
11. Finish the equation: W = E x I
12. Aluminum branch-circuit conductors should be sized one to two sizes larger than copper.
13. A 20-amp breaker should feed a minimum 12-AWG conductor.
14. What would be the minimum service entrance cable size for a 200-amp supply? Answer: 2/0 copper or 4/0 aluminum
Answer Key for Quiz #2
1. Which of the following would describe most residential services? Answer: 120/240-volt
2. A service entrance with four connected conductors is a 3-phase supply.
3. The service drop should not pass closer than 3 feet to the bottom, front or sides of a balcony.
4. The minimum service drop clearance over a $at roof used as a roof garden is 10 feet.
5. Service drops around a swimming pool should be 22 feet above and 10 feet horizontally away. 6. Service drops should never pass closer than 3 feet above the ridge of a conventional pitched roof. 7. Tree limbs should be trimmed back to 5 to 6 feet away from the service drop.
8. An electrical service mast that extends more than 5 feet above the roof surface should be separately supported.
Appendix I: Answer Keys 107 9. Which of the following may also be supported by the electrical service mast?
Answer: none of these
10. Rigid service masts should be secured to the structure every 5 to 6 feet.
11. Which type of cable is listed for direct burial? Answer: UF
12. An underground service entrance is called a service lateral.
13. Square electric meter bases are indicative of a 100-amp supply.
14. Most modern 200-amp electrical meters are marked 200 CL.
15. The minimum conductor size for a 100-amp service is 4-AWG copper or 2-AWG aluminum.
Answer Key for Quiz #3
1. Most jurisdictions require two separate grounding means.
2. The minimum size for a stainless steel, unlisted driven grounding rod is -inch diameter and
8 feet long.
3. T/F: Driven grounding rods can only be perfectly vertical.
4. Which of the following cannot be used as a grounding means?
Answer: gas supply piping
5. T/F: Only panel enclosures containing the service disconnect need to be bonded to ground.
6. The grounded and grounding conductors can share a common bus only in the service panel.
7. The ungrounded and grounding conductors can share a common bus never.
8. Which of the following is an acceptable means of bonding a remote distribution panel? Answer: connecting the enclosure to the grounding bus
9. Conductors between the main service disconnect and the distribution panels are called feeders. Answer Key for Quiz #4
- The minimum service amperage required for a newer single-family home is 100 amps.
- An electrical panel that uses a double-pole breaker to isolate the 120-volt circuits is called a split-bus panel.
- One should be able to shut down the electrical supply with six or fewer moves of the hand.
- The available service amperage is based on the lowest-rated component.
- Most homes constructed between 1930 and 1950 originally had a 60-amp service.
6. Which of the following would not be an electrical panel defect? Answer: wire splices
7. 8. 9.
How to Perform Residential Electrical Inspections 108 Electrical service panels should be in a clear space measuring 30 inches wide by 78 inches high
by 36 inches deep.
Electrical panels do not have to be fully enclosed as long as no hole is bigger than none of
T/F: Water dripping from an electrical panel should be fully investigated by the home inspector.
10. A common cause of arc $ashes when removing panel fronts is incorrect fasteners.
11. Which of the following should the inspector be wearing while evaluating electrical panels?
Answer: all of these
12. Which of the following should be reported as a problem with an electrical panel?
Answer: unlinked double-pole breakers
13. A bonding connection should connect the grounding bus to the electrical enclosure.
Answer Key for Quiz #5
1. Fused main disconnects are usually a maximum of 100 amps. 2. Screw-in fuses are more properly called Edison-base fuses.
3. Upgrading to S-fuses stops over-fusing.
4. Which of the following statements is true about 240-volt breakers?
Answer: 240-volt breakers are connected to two separate bus bars in the panel.
5. GFCI breakers have two conductors.
6. T/F: The inspector will !nd overheating only with Zinsco and FPE breakers.
7. AFCI breakers made by Square D were subject to a recall notice.
8. Zinsco electrical panels are sometimes branded as Sylvania.
9. Electric panel buses colored red, blue and black are indicative of a 3-phase supply. 10. Zinsco electrical panels are problematic due to poor connections to the bus.
11. Fused neutral circuits were common in the 1920s.
Answer Key for Quiz #6, Part 1
1. Which of the following would the inspector defer for a specialist’s evaluation? Answer: single-strand aluminum wiring
2. The earliest residential wiring is called knob-and-tube.
3. The minimum copper wiring size carrying 120 volts should be 14 AWG.
4. A 14-AWG conductor should be connected to a 15-amp fuse or breaker.
Appendix I: Answer Keys 109
5. “Romex” cable that is not actually of the brand Romex® is more properly called type-NM cable. 6. Plastic conduit rated for electrical use is gray in color.
7. Electric water heaters should be fed with 10-AWG minimum copper conductors.
8. T/F: Several grounded conductors can terminate on the same lug.
9. T/F: Anti-oxidant paste should be evident on all aluminum conductors.
10. T/F: The inspector should report all in-panel electrical splices as improper.
11. Wiring closer than 1 inches to the front of a stud requires protection.
12. Unprotected attic electrical wiring should not be within 6 feet of the entrance opening.
13. T/F: Unsupported cable assemblies are acceptable in crawlspaces only. Answer: False
14. Are horizontally mounted face-up countertop receptacles allowed? Answer: No.
15. Bathroom receptacles should be on 20-amp, GFCI-protected circuits.
16. Which of the following is the inspector not required to test for on electrical receptacles?
Answer: voltage drop
17. In a false or bootleg grounded receptacle, the ground wire is connected to the grounded conductor.
18. On a standard 120-volt outlet, the smaller rectangular slot is the ungrounded conductor.
19. The home inspector is required to test a representative number of receptacles.
20. Which is the only approved repair to aluminum wire terminations? Answer: COPALUM
Answer Key for Quiz #6, Part 2
1. 2. 3. 4. 5. 6. 7.
The 4-wire, 240V circuit was required as of 1996.
A 4-wire, 240V cable assembly has two hot, one neutral, one ground conductors.
Kitchen stove circuits are required to be a minimum of 40 amps. Electric clothes dryer circuits are 30-amp.
GFCIs were !rst required in the 1971 NEC® revision.
Kitchen counter GFCIs became a requirement with the adoption of the 1987 NEC® edition. Which of the following locations require GFCI protection?
Answer: all of these
T/F: GFCI receptacles work on only 3-wire circuits. Answer: False
How to Perform Residential Electrical Inspections 110
9. GFCIs can protect receptacles downstream, if properly wired.
10. AFCIs are required to protect bedroom circuits.
11. Which of the following locations require fixed lighting? Answer: kitchens
12. Staircases with six or more risers require a light switch at the top and bottom of the run. 13. Recessed ceiling lights should be rated IC if installed against insulation.