Between about 1965 and 1973, copper wiring in residential electrical systems was sometimes replaced by single-core (solid) aluminum wiring, with each metal identifiable by its color, all due to the sudden escalation of the price of copper.
After ten years of use by homeowners and electricians, inherent weaknesses were discovered in the metal, which led to it not being used as a branching material. Aluminum will fail faster than copper due to certain properties natural to the metal. Neglected connections in sockets, switches, and lights containing aluminum cables become increasingly dangerous over time. Poor connections cause the wiring to overheat, creating a potential fire hazard. Additionally, the presence of single-wire aluminum wiring can void home insurance.
Inspectors can instruct their clients to speak with their insurance agents about whether the presence of aluminum wiring in their home is a hazard, a defect, or a problem that requires changes to their policy language.
Lite House Inspect inspectors will always note the presence of solid aluminum wiring and refer to a professional electrician for further evaluation.
According to the InterNACHI Home Inspection Standards of Practice, a home inspector is required to report single-strand aluminum wiring with a solid conductor if it is observed by the home inspector.
Aluminum Wiring in Older Homes: Facts and Figures
On April 28, 1974, two people died in a house fire in Hampton Bays, New York. Firefighters determined that the fire was caused by a faulty aluminum wire connection at the outlet.
According to the Consumer Product Safety Commission (CPSC), "homes with stranded aluminum wire manufactured before 1972 ["old technology" aluminum wire] are 55 times more likely to have one or more connections reach "fire hazard conditions" than home wiring." with copper."
Is Aluminum Wiring Safe?
Aluminum Wire Identification
Aluminum wires have an aluminum color and are easily distinguished from copper and other metals.
Since the early 1970s, cable tie clamps and equipment 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 an attic or an 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 trade name, such as "Kaiser Aluminum" stamped on the wire sheath. Where the labels are difficult to read, a light can be shone 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 electrical than homes built before or after those years.
Aluminum is a Metal
Aluminum has certain properties that make it an undesirable material as an electrical conductor compared to copper. All of these characteristics lead to loose joints, where there is a risk of fire. These properties are as follows:
Higher electrical resistance
Aluminum has a high resistance to the flow of electrical current, which means that for the same amperage, aluminum conductors must have a larger diameter than copper conductors would require.
Less tractable
Aluminum fatigues and breaks more quickly when subjected to bending and other forms of abuse than copper, which is more ductile. Fatigue causes the wire to break down internally and become increasingly resistant to electrical current, leading to excessive heat build-up.
Galvanic corrosion
In the presence of moisture, aluminum undergoes galvanic corrosion when it comes into contact with certain dissimilar metals.
Oxidation
Exposure to oxygen in the air causes damage to the outer surface of the wire. This process is called oxidation. Aluminum wire oxidizes more easily than copper wire, and the compound created by this process—alumina—is less conductive than copper oxide. Over time, oxidation can damage connections and pose a fire hazard.
Greater malleability
Aluminum is soft and malleable, which means it is highly sensitive to compression. For example, after over-tightening a screw on an aluminum conduit, the wire will continue to deform or "leak" even after the tightening is complete. This deformation creates a loose connection and increases the electrical resistance at that location.
Greater thermal expansion and contraction
Even more than copper, aluminum expands and contracts with temperature changes. Over time, this process will degrade the connection between the conductor and the device. For this reason, aluminum wires should never be inserted into the "stab", "bayonet" or "push" type terminals found on the back of many switches and sockets.
Excessive vibration
Electric current vibrates as it passes through the wiring. These vibrations are more extreme in aluminum than in copper and can cause the connection to loosen over time.
Replace Aluminum Wiring & Options for Repair
Aluminum wiring should be assessed by a qualified electrician who is experienced in evaluating and repairing problems with aluminum wiring. Not all licensed electricians are properly trained to deal with faulty aluminum wiring. CPSC recommends the following two methods for repairing aluminum conduit:
Reconnect the home with copper wire. Although this is the most efficient method, rewiring is expensive and impractical in most cases.
Use copalum folds. A crimp connector repair consists of connecting a piece of copper wire to an existing aluminum wire tap circuit using a specially designed metal ferrule and a powered crimp tool. This special connector can only be installed correctly with the appropriate AMP tool. An insulating sleeve is placed around the crimp connector to complete the repair. Although effective, they are expensive (usually around $50 per outlet, switch, or light fixture).
Although CPSC does not recommend these as permanent repair methods for defective aluminum conduit, the following methods may be considered:
Application of antioxidant paste. This method can be used for wires that are multi-stranded or wires that are too large to be effectively crimped.
Pigtailing. This method involves connecting a short piece of copper wire to an aluminum wire using a twist-on connector. The copper wire is connected to a switch, wall outlet, or other termination device. This method is only effective if the connections between the aluminum wires and the copper pigtails are extremely reliable. Pigtailing with some connector types, even though Underwriters Laboratories may currently list them for a given application, can lead to increased risk. Also, note that pigtailing will increase the number of connections that must all be maintained. Aluminum Wiring Repair (AWR), Inc., Aurora, Colo., advises that pigtailing can be useful as a temporary fix or in isolated applications, such as installing a ceiling fan.
CO/ALR connection. According to the CPSC, these devices cannot be used for all parts of the wiring system, such as ceiling fixtures or permanently connected appliances, and as such, CO/ALR connections cannot represent a complete repair. Also, according to AWR, these connections often loosen over time.
Alumicon. Although AWR believes this method can be an effective temporary fix, they caution that it has little history and that they are larger than copper collars and are often applied incorrectly.
Replace certain types of equipment and connections prone to failure with others that are more compatible with aluminum wire.
Remove flammable materials from the vicinity of the connections.
In short, aluminum wiring can be a fire hazard due to the natural properties of the metal.
Inspectors should be able to identify this type of material.