Common Electrical Conductor Types

by Nick Gromicko, Rob London and Kenton Shepard

Poorly installed and maintained electrical cables are a common cause of electrical fires in homes. Many older homes contain wiring that is now considered obsolete or dangerous. InterNACHI inspectors should understand the basic distinctions between the different types of cable systems so that they can identify unsafe conditions.
Romex Cables
Romex is the trade name for a type of electrical conductor with non-metallic sheathing that is commonly used as residential branch wiring. The following are a few basic facts about Romex wiring:
  • Romex is a common type of residential wiring that is categorized by the National Electrical Code (NEC) as underground feeder (UF) or non-metallic sheathed cable (NM and NMC).
  • NM and NMC conductors are composed of two or more insulated conductors contained in a non-metallic sheath. The coating on NMC cable is non-conducting, flame-resistant and moisture-resistant. Unlike other cables commonly found in homes, they are permitted in damp environments, such as basements.
  • Underground feeder conductors appear similar to NM and NMC cables except that UF cables contain a solid plastic core and cannot be “rolled” between fingers.
The following NEC regulations apply to Romex conductors:
  • They are not permitted in residential construction higher than three stories, or in any commercial construction.
  • They must be protected, secured and clamped to device boxes, junction boxes and fixtures.
  • Support devices that may damage the cables, such as bent nails and overdriven staples, are not permitted.
  • NM and NMC cables should be secured at intervals that do not exceed 4½ feet, and they should be secured within 12 inches of junction boxes and panels to which they are attached. Cables that do not comply with this rule can sag and are vulnerable to damage.
  • They are intended as permanent wiring in homes and should not be used as a substitute for appliance wiring or extension cords.

Note:  Some communities have never allowed the use of Romex wiring in residential construction. Armored cable is typically used in these communities.

Armored Cables (AC)
Armored cable (AC), also known as BX, was developed in the early 1900s by Edwin Greenfield. It was first called “BX” to abbreviate “product B – Experimental,” although AC is far more commonly used today. Like Romex cables, they cannot be used in residences higher than three stories, and the rules for protection and support of AC wiring are essentially the same as the rules for Romex. Unlike Romex, however, AC wiring has a flexible metallic sheathing that allows for extra protection. Some major manufacturers of armored cable are General Cable, AFC Cable Systems, and United Copper Systems.
Service Entry (SE) Conductors
These cables begin at the splice and enter the meter. They are not permitted inside homes, with the exception of “style R” SE cable that can serve as interior wiring in branch circuits for ovens and clothes dryers. Style R cables should be clearly marked on their jacket surfaces.
Knob-and-Tube (KT) Wiring
Most houses constructed prior to World War II were wired using the knob-and-tube method, a system that is now obsolete. They are more difficult to improve than modern wiring systems and are a fire hazard. Knob-and-tube wiring is supported with ceramic knobs, and runs intermittently though ceramic tubes beneath framing and at locations where the wires intersect. Whenever an inspector encounters knob-and-tube wiring, s/he should identify it as a defect and recommend that a qualified electrician evaluate the system. The following are a few reasons why inspectors should be wary of this old wiring system:
  • The dissipated heat from knob-and-tube wiring can pose a fire hazard if the wires are enveloped in building insulation. A possible exception is fiberglass insulation, which is fire-resistant, although even this type of insulation should not cover knob-and-tube wiring. The homeowner or an electrician should carefully remove any insulation that is found surrounding KT wires.
  • Knob-and-tube wiring is more vulnerable to damage than modern wiring because it is insulated with fiber materials and varnish, which can become brittle.
  • Some insurance companies refuse to write fire insurance for houses with this type of wiring, although this may be remedied if an electrician can verify that the system is safe.
  • Disregarding any inherent inadequacies, existing KT cable systems are likely to be unsafe because they are almost guaranteed to be at least 50 years old.
In summary, inspectors should understand the different types of conductors that are commonly found in homes. 



Arc Fault Circuit Interrupters

by Nick Gromicko, Rob London and Kenton Shepard
Arc Fault Circuit Interrupters (AFCIs) are special types of electrical outlets and circuit breakers designed to detect and respond to potentially dangerous electrical arcs in home branch wiring.

How do they work?
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. They also must be capable of distinguishing safe, normal arcs, such as those created when a switch is turned on or a plug is pulled from a receptacle, from arcs that can cause fires. An AFCI can detect, recognize, and respond to very small changes in wave pattern.

What is an arc?
When an electric current crosses an air gap from an energized component to a grounded component, it produces a glowing plasma discharge known as an arc. For example, a bolt of lightening is a very large, powerful arc that crosses an atmospheric gap from an electrically charged cloud to the ground or another cloud. Just as lightning can cause fires, arcs produced by domestic wiring are capable of producing high levels of heat that can ignite their surroundings and lead to structure fires.

According to statistics from the National Fire Protection Agency for the year 2005, electrical fires damaged approximately 20,900 homes, killed 500 people, and cost $862 million in property damage. Although short-circuits and overloads account for many of these fires, arcs are responsible for the majority and are undetectable by traditional (non-AFCI) circuit breakers.

Where are arcs likely to form?
Arcs can form where wires are improperly installed or when insulation becomes damaged. In older homes, wire insulation tends to crystallize as it ages, becoming brittle and prone to cracking and chipping. Damaged insulation exposes the current-carrying wire to its surroundings, increasing the chances that an arc may occur.

Situations in which arcs may be created:
  • electrical cords damaged by vacuum cleaners or trapped beneath furniture or doors.
  • damage to wire insulation from nails or screws driven through walls.
  • appliance cords damaged by heat, natural aging, kinking, impact or over-extension.
  • spillage of liquid.
  • loose connections in outlets, switches and light fixtures.
Where are AFCIs required?
Locations in which AFCIs are required depend on the building codes adopted by their jurisdiction. Inspectors are responsible for knowing what building codes are used in the areas in which they inspect.

The 2006 International Residential Code (IRC) requires that AFCIs be installed within bedrooms in the following manner:
E3802.12 Arc-Fault Protection of Bedroom Outlets. All branch circuits that supply120-volt, single-phase, 15- and 20-amp outlets installed in bedrooms shall be protected by a combination-type or branch/feeder-type arc-fault circuit interrupter installed to provide protection of the entire branch circuit.

Exception: The location of the arc-fault circuit interrupter shall be permitted to be at other than the origination of the branch circuit, provided that:
  1. The arc-fault circuit interrupter is installed within 6 feet of the branch circuit overcurrent device as measured along the branch circuit conductors, and
  2. The circuit conductors between the branch circuit overcurrent device and the arc-fault circuit interrupter are installed in a metal raceway or a cable with metallic sheath.

The National Electrical Code (NEC) offers the following guidelines concerning AFCI placement within bedrooms:
Dwelling Units. All 120-volt, single phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit in family rooms, dining rooms, living rooms, parlors, libraries, dens, sun rooms, recreation rooms, closets, hallways, or similar rooms or areas shall be protected by a listed arc-fault circuit interrupter, combination-type installed to provide protection of the branch circuit.

Home inspectors should refrain from quoting exact code in their reports. A plaintiff's attorney might suggest that code quotation means that the inspector was performing a code inspection and is therefore responsible for identifying all code violations in the home.  Some jurisdictions do not yet require their implementation in locations where they can be helpful.
What types of AFCIs are available?
The four most common types of AFCIs are as follows:
  • Branch/feeder—installed at the main electrical panel or sub-panel.
  • Outlet circuit—installed in a branch-circuit outlet.
  • Combination—complies with the requirements of both the branch/feeder and the outlet circuit AFCIs.
  • Cord—a plug-in device connected to the receptacle outlet.

Nuisance Tripping

An AFCI might activate in situations that are not dangerous and create needless power shortages. This can be particularly annoying when an AFCI stalls power to a freezer or refrigerator, allowing its contents to spoil. There are a few procedures an electrical contractor can perform in order to reduce potential “nuisance tripping," such as:
  • Check that the load power wire, panel neutral wire and load neutral wire are properly connected.
  • Check wiring to ensure that there are no shared neutral connections.
  • Check the junction box and fixture connections to ensure that the neutral conductor contacts a grounded conductor.
Arc Faults vs. Ground Faults
It is important to distinguish AFCI devices from Ground Fault Circuit Interrupter (GFCI) devices. GFCIs detect ground faults, which occur when current leaks from a hot (ungrounded) conductor to a grounded object as a result of a short-circuit. This situation can be hazardous when a person unintentionally becomes the current’s path to the ground. GFCIs function by constantly monitoring the current flow between hot and neutral (grounding) conductors, and activate when they sense a difference of 5 milliamps or more. Thus, GFCIs are intended to prevent personal injury due to electric shock, while AFCIs prevent personal injury and property damage due to structure fires.
In summary, AFCIs are designed to detect small arcs of electricity before they have a chance to lead to a structure fire. 

Electrical Safety

Electricity is an essential part of our lives. However, it has the potential to cause great harm. Electrical systems will function almost indefinitely, if properly installed and not overloaded or physically abused. Electrical fires in our homes claim the lives of 485 Americans each year and injure 2,305 more. Some of these fires are caused by electrical system failures and appliance defects, but many more are caused by the misuse and poor maintenance of electrical appliances, incorrectly installed wiring, and overloaded circuits and extension cords.  Some safety tips to remember:
  • Never use anything but the proper fuse to protect a circuit.
  • Find and correct overloaded circuits. 
  • Never place extension cords under rugs. 
  • Outlets near water should be GFCI-type outlets. 
  • Don't allow trees near power lines to be climbed. 
  • Keep ladders, kites, equipment and anything else away from overhead power lines. 
Electrical Panels
Electricity enters the home through a control panel and a main switch where one can shut off all the power in an emergency. These panels are usually located in the basement. Control panels use either fuses or circuit breakers. Install the correct fuses for the panel. Never use a higher-numbered fuse or a metallic item, such as a penny. If fuses are used and there is a stoppage in power, look for the broken metal strip in the top of a blown fuse. Replace the fuse with a new one marked with the correct amperage. Reset circuit breakers from "off" to "on." Be sure to investigate why the fuse or circuit blew. Possible causes include frayed wires, overloaded outlets, or defective appliances. Never overload a circuit with high-wattage appliances. Check the wattage on appliance labels. If there is frayed insulation or a broken wire, a dangerous short circuit may result and cause a fire. If power stoppages continue or if a frayed or broken wire is found, contact an electrician.
Outlets and Extension Cords

Make sure all electrical receptacles or outlets are three-hole, grounded outlets. If there is water in the area, there should be a GFCI or ground-fault circuit interrupter outlet. All outdoor outlets should be GFCIs. There should be ample electrical capacity to run equipment without tripping circuit breakers or blowing fuses. Minimize extension cord use. Never place them under rugs. Use extension cords sparingly and check them periodically. Use the proper electrical cord for the job, and put safety plugs in unused outlets.

Electrical Appliances

Appliances need to be treated with respect and care. They need room to breathe. Avoid enclosing them in a cabinet without proper openings, and do not store papers around them. Level appliances so they do not tip. Washers and dryers should be checked often. Their movement can put undue stress on electrical connections. If any appliance or device gives off a tingling shock, turn it off, unplug it, and have a qualified person correct the problem. Shocks can be fatal. Never insert metal objects into appliances without unplugging them. Check appliances periodically to spot worn or cracked insulation, loose terminals, corroded wires, defective parts and any other components that might not work correctly. Replace these appliances or have them repaired by a person qualified to do so.
Electrical Heating Equipment

Portable electrical heating equipment may be used in the home as a supplement to the home heating system. Caution must be taken when using these heating supplements. Keep them away from combustibles, and make sure they cannot be tipped over. Keep electrical heating equipment in good working condition. Do not use them in bathrooms because of the risk of contact with water and electrocution. Many people use electric blankets in their homes. They will work well if they are kept in good condition. Look for cracks and breaks in the wiring, plugs and connectors. Look for charred spots on both sides. Many things can cause electric blankets to overheat. They include other bedding placed on top of them, pets sleeping on top of them, and putting things on top of the blanket when it is in use. Folding the blankets can also bend the coils and cause overheating.

Electricity is important to the workings of the home, but can be dangerous, especially to children. Electrical safety needs to be taught to children early on. Safety plugs should be inserted in unused outlets when toddlers are in the home. Make sure all outlets in the home have face plates. Teach children not to put things into electrical outlets and not to chew on electrical cords. Keep electrical wiring boxes locked. Do not allow children to come in contact with power lines outside. Never allow them to climb trees near power lines, utility poles or high tension towers.
Electricity and Water

A body can act like a lightning rod and carry the current to the ground. People are good conductors of electricity, particularly when standing in water or on a damp floor. Never use any electrical appliance in the tub or shower. Never touch an electric cord or appliance with wet hands. Do not use electrical appliances in damp areas or while standing on damp floors. In areas where water is present, use outlets with GFCIs. Shocks can be fatal.
Animal Hazards

Mice and other rodents can chew on electrical wires and damage them. If rodents are suspected or known to be in the home, be aware of the damage they may cause, and take measures to get rid of them.
Outside Hazards

There are several electrical hazards outside the home. Be aware of overhead and underground power lines. People have been electrocuted when an object they are moving has come in contact with the overhead power lines. Keep ladders, antennae, kites and poles away from power lines leading to the house and other buildings. Do not plant trees, shrubs or bushes under power lines or near underground power lines. Never build a swimming pool or other structure under the power line leading to your house. Before digging, learn the location of underground power lines.

Do not climb power poles or transmission towers. Never let anyone shoot or throw stones at insulators. If you have an animal trapped in a tree or on the roof near electric lines, phone your utility company. Do not take a chance of electrocuting yourself. Be aware of weather conditions when installing and working with electrical appliances. Never use electrical power tools or appliances with rain overhead or water underfoot. Use only outdoor lights, fixtures and extension cords. Plug into outlets with a GFCI. Downed power lines are extremely dangerous. If you see a downed power line, call the electric company, and warn others to stay away. If a power line hits your car while you are in it, stay inside unless the car catches fire. If the car catches fire, jump clear without touching metal and the ground at the same time.
  • Routinely check your electrical appliances and wiring.
  • Hire an InterNACHI inspector. InterNACHI inspectors must pass rigorous safety training and are knowledgeable in the ways to reduce the likelihood of electrocution.
  • Frayed wires can cause fires. Replace all worn, old and damaged appliance cords immediately.
  • Use electrical extension cords wisely and don't overload them.
  • Keep electrical appliances away from wet floors and counters; pay special care to electrical appliances in the bathroom and kitchen.
  • Don't allow children to play with or around electrical appliances, such as space heaters, irons and hair dryers.
  • Keep clothes, curtains and other potentially combustible items at least 3 feet from all heaters.
  • If an appliance has a three-prong plug, use it only in a three-slot outlet. Never force it to fit into a two-slot outlet or extension cord.
  • Never overload extension cords or wall sockets. Immediately shut off, then professionally replace, light switches that are hot to the touch, as well as lights that flicker. Use safety closures to childproof electrical outlets.
  • Check your electrical tools regularly for signs of wear. If the cords are frayed or cracked, replace them. Replace any tool if it causes even small electrical shocks, overheats, shorts out or gives off smoke or sparks.

Home Grounding Electrodes


by Nick Gromicko, Rob London and Kenton Shepard
Electrical grounding systems divert potentially dangerous electrical currents by providing a path between a building’s service boxGrounding Rod and the earth. Lightning and static electricity are the most common sources of dangerous or damaging charges that can be dissipated through a grounding system. Grounding electrodes are connected to the building’s electrical system through grounding electrode conductors, also known as ground wires. A number of different metal alloys can function as grounding electrodes, the most common of which are the focus of this article.  
Requirements for electrodes and ground wires:
  • Aluminum has a tendency to corrode and should not be used in ground wires unless they are insulated. Moisture and mineral salts from masonry are common causes of corrosion to uninsulated aluminum. It is also a poorer conductor than copper. Aluminum wires in grounding systems are not permitted in Canada.
  • Since grounding electrodes are not insulated, they can never be made of aluminum.
  • If more than one electrode is present, they must be connected to each other with a bonding jumper.

Common Types of Grounding Electrodes Grounding Rods

The most common form of grounding electrode is a metal rod that is hammered into the ground so that its entire length is submerged. InterNACHI recommends that the rod be inserted vertically and in one piece, but this is not always possible in rocky areas. If the rod is hammered into sub-surface rocks it might become scratched and lose its cladding. Rust can accumulate on exposed iron or steel and degrade the conductive capacity of the rod. Unfortunately, this rust will rarely be visible to an inspector.
Electricians have been known to cut the rod when they have difficulty inserting its entire length beneath the ground. This practice violates code and can be a safety hazard. Inspectors should look for the following signs that indicate that a grounding rod has been shortened:
  • Rust at the rod’s top. Grounding rods have a corrosion-resistant coating but are usually made of steel or iron and are vulnerable to rusting at any location that the rod is cut.
  • Most rods have an etched label on their top. If this label is missing it is likely that the rod has been cut.

Inspectors should bear in mind that utility companies sometimes allow ground rods to be shortened. A qualified electrician can test whether a shortened rod is an adequate grounding electrode.

If accessible, inspectors should check the condition of the clamp that connects the grounding rod to the ground wire. Clamps should be made of bronze or copper and be tightly fastened. Requirements for rod length, thickness, and protective coating are addressed in the 2006 International Residential Code (IRC) as follows:

Rod and pipe electrodes not less than 8 feet (2438 mm) in length and consisting of the following materials shall be considered as a grounding electrode:
  1. Electrodes of pipe or conduit shall be not smaller than trade size ¾ (metric designator 21) and, where of iron or steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection.
  2. Electrodes of rods of iron or steel shall be at least 5/8 inch (15.9 mm) in diameter. Stainless steel rods less than 5/8 inch (15.9mm) in diameter, nonferrous rods or their equivalent shall be listed and shall be not less than 1⁄2 inch (12.7mm) in diameter.


  • Although the 2006 IRC does not mention whether the rod may be driven at an angle, the 1998 California Electrical Code allows for a maximum oblique angle of 45 degrees from the vertical.
  • An electrician can install two grounding rods if necessary. They should be at least 6 feet apart from one another.
  • In Canada, grounding rods should be 10 feet long and two are required. 

Concrete-Encased Electrodes (Ufer Grounds)

This electrical grounding technique was invented during World War II in Arizona, and is commonly called “Ufer” after its creator, Herbert G. Ufer. The United States Army was concerned that lightning or static electricity could cause the accidental detonation of explosives that were stored in igloo-shaped vaults. The desert climate restricted the usefulness of grounding rods, which would have to be driven hundreds of feet into the dry earth in order to be effective. Ufer advised the military to connect ground wires into the concrete-encased steel reinforcement bars (re-bar) of the bomb vaults in order to dissipate electricity effectively into the ground. Testing confirmed his theory that the relatively high conductivity of concrete would allow electric current to dissipate into a large surface area of earth. The Ufer method is more common in newer residential construction and requires a metal frame. It might be difficult for an inspector to detect this type of electrode. The 2006 IRC details Ufer grounds as follows:
An electrode encased by at least 2 inches (51 mm) of concrete, located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 20 feet (6096 mm) of one or more bare or zinc-galvanized or three electrically conductive coated steel reinforcing bars or rods of not less than 1/2 inch (12.77 mm) diameter or consisting of at least 20 (6096 mm) feet of bare copper conductor not smaller than 4 AWG shall be considered as a grounding electrode. Reinforcing bars shall be permitted to be bonded together by the usual tie wires or other effective means.
Metal Underground Water Pipes
A building’s plumbing system can be connected to the ground wire and function as a grounding electrode. For some time, this was the only mandatory grounding electrode type and it was generally preferred over other methods. As of 1987, however, this method became the only one that must be supplemented with another type of electrode. This transition is due to the increased popularity of nonconductive dielectric unions and plastic pipes. When plumbing has been replaced with plastic pipes a notice is required to be placed at the electrical service panel that states that there is a non-metallic water service. Inspectors will not be able to tell if outdoor water pipes that run to street water mains have been replaced with plastic components.
Inspectors should check for the following:
  • Ground wires should be firmly attached to water pipes close to the point of entry to the building. A ground wire that is loosely tied around a pipe is inadequate.
  • Gas pipes should never be used as grounding conductors. They usually are made of plastic at the exterior of the home and carry flammable gases that may ignite if exposed to electrical current.

The 2006 IRC states the following about water pipe electrodes:

A metal underground water pipe that is in direct contact with the earth for 10 feet (3048 mm) or more, including any well casing effectively bonded to the pipe and that is electrically continuous by bonding around insulating joints or insulating pipe to the points of connection of the grounding electrode conductor and the bonding conductors, shall be considered as a grounding electrode. Interior metal water piping located more than 5 feet (1524 mm) from the entrance to the building shall not be used as part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system.

Less Common Grounding Electrodes
The previously mentioned grounding electrodes constitute the vast majority of grounding systems that inspectors will encounter. The two electrodes described below are far less common, although they are recognized by the IRC. Inspectors might not be able to verify their presence. The 2006 IRC explains them as follows:
Plate Electrodes
A plate electrode that exposes no less than 2 square feet (0.186 m2) of surface to exterior soil shall be considered as a grounding electrode. Electrodes of iron or steel plates shall be at least 1⁄4 inch (6.4mm) in thickness. Electrodes of nonferrous metal shall be at least 0.06 inch (1.5mm) in thickness. Plate electrodes shall be installed not less than 30 inches (762 mm) below the surface of the earth.
Ground Ring Electrodes
A ground ring encircling the building or structure, in direct contact with the earth at a depth below the earth’s surface of not less than 2.5 feet, consisting of at least 20 feet of bare copper conductor not smaller than No. 2 shall be considered as a grounding electrode.
In summary, a variety of home service grounding electrodes can be used to safely route unexpected electrical charges away from places that they can cause harm. Inspectors should be aware of how they differ from one another and be prepared to spot defects.

Aluminum Wiring

By Nick Gromicko, Rob London and Kenton Shepard
Between approximately 1965 and 1973, aluminum wiring was sometimes substituted for copper branch-circuit wiring in residential electrical systemsAluminum and copper wiring. Each metal is clearly identifyable by its color 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 lead 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 fixtures containing aluminum wiring become increasingly dangerous over time. Poor connections cause wiring to overheat, creating a potential fire hazard. In addition, the presence of aluminum wiring may void a home’s insurance policies. Inspectors may instruct their clients to talk with their insurance agents about whether the presence of aluminum wiring in their home is a problem that requires changes to their policy language.
Aluminum as a Metal

Aluminum possesses certain qualities that, compared with copper, make it an undesirable material as an electrical conductor. These qualities all lead to loose connections, where fire hazards become likely. These qualities are as follows:

  • high electrical resistance. Aluminum has a high resistance to electrical current flow, 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 when subjected to bending and other forms of abuse than copper, which is more ductile. Fatigue will cause the wire to break down internally and wukk 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 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. As time passes, oxidation can deteriorate connections and present a fire 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 “flow” 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” type 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 discernable 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" 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 specific 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 qualified 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 following corrective actions may be taken:

  • Rewire the home with copper wire. While this is the most effective method, rewiring is expensive and impractical, in most cases.
  • Splice the aluminum wire to copper wire at the connections using approved wire nuts (called "pigtailing"). This method is only effective if the connections between the aluminum wires and the copper pigtails are extremely reliable. Pigtailing with some types of connectors, even though they might be presently listed by Underwriters Laboratories for the application, can lead to increasing the hazard. Also, beware that pigtailing will increase the number of connections, all of which must be maintained.
  • 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.
  • All connections should be checked and an anti-oxidant paste applied.
  • Copalum crimps can be installed. Although effective, they are expensive (typically around $50 per outlet, switch or light fixture).
In summary, aluminum wiring can be a fire hazard due to inherent qualities of the metal. Inspectors should be capable of identifying this type of wiring.

Tribuzio Home Inspection Services, Copyright 2008

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