Electric wiring runs throughout the structure of a building to supply power to receptacles/outlets, lights and devices. Modern wiring typically consists of high-grade copper conductors set within colored insulating polyvinyl chloride (PVC) jackets. Smaller gauge wires that carry smaller electrical loads are typically single strands and larger diameter wires used for carrying larger electrical loads are typically made from multiple single strands, braided together.
In the mid-1960s and early-1970s some manufacturers decided to produce cables which used aluminum conductors instead of copper. This was mainly due to the increase in cost of copper as a material.
Unfortunately, over time it became clear that aluminum wiring carries inherent defects which can lead to death, injury and/or fire hazards. This article will explain why defects occur, how you can identify aluminum wiring, and what needs to be done should aluminum wiring be encountered.
Cloth-covered wiring is also a concern with buildings of this age. Within article The Dangers of Cloth-Covered Electrical Wiring we discuss the issues associated with cloth-covered insulators used in electrical wiring.
Why is Aluminium Unsuitable as a Conductor?
Aluminum is a naturally occurring metal which is mined and produced across the world. The material has several favorable characteristics including being a good conductor of electricity, resistance to rust and light weight.However, when used as an electrical conductor, the material has several undesirable qualities.
The main problem with aluminum wiring is that cabling can overheat, cables can break down, loose connections can form, and cables can “creep” (move) resulting in overheating and fire risks. It should be noted that these issues are usually associated with aluminum branch wiring within buildings, and not larger supply/infrastructure cables.
The negative qualities of aluminum as a conductor are listed as follows:
Aluminum Has a Higher Electrical Resistance When Compared to Copper
While aluminum conducts electricity, it does not do it as well as copper. As a material, it is of a higher resistance than copper. This results in the need for larger thickness (diameter) conductors. As well as making cables thicker (compared to a copper alternative), if a cable was inadvertently undersized as a direct comparison for copper, there may potentially be an overheating/fire risk.
Aluminum Naturally Oxidizes
Aluminum naturally oxidizes, creating a protective coating over the outer edge of the wire. For electrical cables and wiring this is a disadvantage. Where aluminum is exposed to air, e.g. cables and wiring at connection points/terminals, the oxidized protective outer coating can create an area of poor connection. This can lead to increased electrical resistance, overheating and potential fires.
Aluminum Expands and Contracts
Aluminum readily expands and contracts. Regular lengthening and shortening at connection points due to changes in temperature can loosen connections, creating overheating and fire risks.
Aluminum is Subject to Metal Fatigue
Aluminum is more subject to metal fatigue. The material is not as ductile as copper and if it is repeatedly moved, bent or twisted the inner conductors can break. If a cable is subject to regular movement or was excessively handled during installation it could be damaged, creating a potential fire risk.
In addition, the material is very malleable (easily compressed). If a screw is inadvertently over-tightened at a connection during installation, the material can become overly compressed, creating a poor connection leading to overheating which may create a fire risk.
Aluminum Can Corrode
If subjected to moisture, galvanic corrosion can occur between the aluminum conductor and dissimilar metals e.g. copper connection/termination points. This can create an area of poor connection and increased resistance leading to overheating and fires.
Aluminum is Subject to Alternating Current (AC) Vibrations
Electrical alternating current (AC) switches from positive to negative values at a rate of 60-Hertz (Hz) or 60 times a second in the United States. As a conductor, aluminum is more susceptible to vibrations from AC current within the wire which can cause the wire to vibrate and connections to loosen over time. This can lead to overheating and fire risks.
How Can Aluminum Wiring be Identified?
Aluminum wiring was most prominent between 1965 and 1973, therefore buildings of that era are most likely to be affected. To the uniformed, aluminum wiring is often indistinguishable from its copper counterpart as it’s hidden behind walls and ceilings along with panelboard and receptacle covers.
Manufacturing details on the outer sheath of the cable do sometimes note if the cable is aluminum. Watch out also for areas on cables where “AL” or “ALUM” may be stamped or printed on the outside jacket. On some cables, CO/ALR was also stamped/marked on cables which stands for copper/aluminum revised. Various companies manufactured aluminum wiring most notably Kaiser Aluminum. A tell-tale sign of aluminum wiring is the gray/ silver color of the aluminum wire material itself. By removing a cover to a panelboard, receptacle or switch, it is usually possible to see if the cable is a gray/silver color. Copper on the other hand is an orange/brown color, or green if oxidized.
Although aluminum wiring might cause issues without warning, some tell-tale signs of defects might become apparent indicating a problem, as follows:
- Burned or warped receptacles/switch cover plates
- Unusually warm receptacles and switch cover plates (hot to the touch)
- Sparks or smoke emitting from receptacles and switch cover plates
- Odor of burning plastic
- Period flickering of lights
- Issues with appliances, outlets, light fittings etc.
Do not to touch electrical components when removing panelboards, receptacle or switch covers. We recommend you use a reputable electrician who should be able to easily identify if aluminum wiring is present in your building.
Should I be Concerned and How Can I Rectify Aluminum Wiring?
As we have learnt, aluminum wiring is a defective material and can be dangerous. What should you do if you discover aluminum wiring?
Given the likely age of the wiring, between 1965 and 1973, associated defects and safety risks, the best solution to rewire your building. You should replace all aluminum cable and wires with modern copper. The cost to re-wire your building can be between $6.50 to $12.50 per square foot depending on the complexity and size of the project.
If re-wiring your building is not a feasible option, two main alternatives are available:
Crimp the Connection Points
Crimped connections can be installed on the ends of the original aluminum wiring. The crimp fittings are compressed onto the aluminum wires and attach a small section of copper wire which connects into the termination point. The crimp joint is sealed with a protective insulating jacket. In this method COPALUM crimps and a specialized crimping tool must be used. This typically costs $75 to $100 per receptacle, light fixture etc.
Pigtail the Connection Points
As aluminum wiring is more susceptible to damage at tight radiuses and connection points, the cable can be spliced, in a repair known as pig tailing. In this repair, the aluminum cable is removed at the receptacle/switch outlets and panelboard ends. A new section of copper cable is installed at these locations which is then connected to the aluminum wire, usually using screw connectors. This process is similar to the crimp method noted above, but longer sections of cables are replaced, rather than just the ends that enter into terminal points.
Alternative methods such as applying antioxidizing paste or other crimp-type connections have been trialed and are generally classed as temporary repairs. Crimp fittings and pigtail methods need specialist knowledge, tools and equipment and should only be completed by a professional certified and competent electrician.
Remember, just because your building was not necessarily constructed at the time that aluminum wiring was used, it may still contain it. Leftover supplies of aluminum wiring will have been used in buildings by electricians after 1973. Circuits within your building may have been added or modified and these works could have been completed using aluminum wiring. Aluminum wiring may be hidden and concealed within the structure of your building.
If you are concerned about aluminum wiring in your home or building then we recommend you contact a reputable electrician.