Single Strand Aluminum Wiring – Is it Safe?
According to the Consumer Product Safety Commission (CPSC): Houses wired with single strand aluminum wire that is used for 15 and 20 amp circuits are 55 times more likely to have one or more connections reach “fire hazard conditions” than homes wired with copper. This wiring was primarily used in houses built between 1965 and 1972. If you are looking to buy a house built in this era, you want to check for this type of wiring during your home inspection and understand what to do about it.
Why are houses wired with this wiring during this time period?
The demand for copper during the Vietnam War caused the price of copper to spike, so more affordable alternatives were sought.
Why is single stand Aluminum a fire hazard?
Compared to copper, aluminum has distinct disadvantages as a conductor.
- Aluminum is less ductile than copper making it more prone to metal fatigue when bending. Fatigued metal will not conduct electricity efficiently which can lead to overheating.
- Aluminum is more prone to thermal expansion and contraction compared to copper, so wires can loosen over time. Loose connections lead to arcing (think sparks) and arcing leads to fires.
- Aluminum has a higher resistance than copper so you must use a larger diameter wire to pass the same amount of current. These larger wires are more difficult to secure reliably which can also lead to loose connections and arcing at wire terminations.
- Aluminum is more susceptible to oxidation and galvanic corrosion than copper. These forces can deteriorate the wire and make connections less reliable.
Where can I look to see if my house has aluminum wiring?
The best place to check the type of wiring in your house is inside your electric panel. This should ONLY be done by a licensed electrician or a home inspector. You need to remove the dead front cover to the electric panel to see the wiring and this should only be done by trained professionals as it is a safety risk.
Check the terminations for the wires inside the panel and also look for extensive use of wire nuts and crimps that could indicate a prior repair.
If you can see the cable wiring you may even be able to read the listing on the jacket: look for AL in the listing.
What do I do if my house has single strand aluminum wire?
Single strand aluminum wiring, when used for 15 and 20 amp circuits, should be evaluated by a licensed electrician who is experienced in evaluating and correcting aluminum wiring problems. It is important to understand a few basics. The initial versions of this wire were manufactured with an aluminum alloy called AA-1350. This older alloy was especially soft and problematic and houses wired with single strand aluminum between 1965 and 1972 would be wise to replace this wiring. After 1972, manufacturers of aluminum wire changed to an alloy called AA8000. This proved to be a superior conductor and while this still poses some risk, there are some repairs that can be made to the post-1972 aluminum wire that can render the system safe.
According to the CPSC, there are only two safe ways to repair single-strand aluminum wiring from this era.
- Rewire the home with copper wire. This is the most effective repair and can be done by any licensed electrician, but it is also the most expensive repair. Homes wired with the older AA-1350 alloy should probably choose this option.
- Use CPSC approved crimping devices. Copalum and AlumiConn are two examples of crimping devices that can be used. Here is a video showing the installation of an AlumiConn crimp:
Is all aluminum wiring bad?
No, no and no! We still use stranded aluminum wiring in houses today. We have used it for years and it has never been discontinued or recalled. Stranded aluminum wiring is safe and has been performing as intended for decades. Do not confuse stranded aluminum wire used for 240-volt circuits with single strand used for 15 and 20 amp, 120-volt circuits.
The stranded aluminum wire is not subject to the same loose connection problems as the single strand and anti-occident paste can be used at terminations to reduce risks from oxidation and corrosion.
Believe it or not, we even use some single strand wiring today: for 30 amp, 240 circuits you may find it in service for fixtures like dryers and AC circuits. This is code approved and apparently, safe, though this installation is much less common than stranded aluminum which is ubiquitous.
I hope this article helps explain some common questions about aluminum wiring. Remember, happy home buyers are informed home buyers.