This picture is a perfect example of the problems that are associated with Aluminum wiring. Note letters A and B (the insulation jackets are melted), which I will explain "Why" in the third paragraph and C (mixing copper wiring with aluminum wiring on the same breaker). Aluminum wiring can not be mixed with copper wiring and breakers can not be double tapped with two wires, unless designated by manufacturer and the breaker connnection will contain a special clip for double tapping. Aluminum wiring is very easy to identify due to it's obvious aluminum color. Aluminum wiring is not to be confused with tin coated copper which looks similar to aluminum wiring but aluminum wiring has distinguishing characteristics and is a solid conductor.
During the 1970's, aluminum (instead of copper) wiring became quite popular and was extensively used throughout the United States. Since that time, aluminum wiring has been implicated in a number of house fires, which caused jurisdictions to no longer permit aluminum wiring in new installations. I highly recommend that you do not use aluminum wiring for any type of new installation. But don't panic if your house does contain aluminum wiring. Aluminum wiring, when properly installed, can be just as safe as copper wiring. Aluminum wiring is, however, very unforgiving of improper installations. I will cover a bit of the theory behind potential electrical problems, and what you can do to make your wiring (in your home) safe.
The main problem that exists with aluminum wiring is a phenomenon known as "cold creep". When aluminum wiring warms up, it expands. When it cools down, it contracts. Unlike copper, when aluminum goes through a number of warm/cool cycles it loses a bit of it's tightness over time. To make the problem worse, aluminum oxidizes (or corrodes) when in contact with certain types of metal, so the resistance of the connection will go up. Which causes the aluminum wiring to heat up and corrode/oxidize even more. Eventually the wire may start to become very hot and melt the insulation jacket (shown in the picture above) or the fixture that it's attached to, and possibly even cause a fire.
Since people usually encounter aluminum wiring when they move into a house that was built in the 70's, I will cover the basic points of safe aluminum wiring. I suggest that, if you're considering purchasing a home with aluminum wiring or have discovered aluminum wiring after moving in, that you hire a licensed electrician to inspect the wiring for the following:
1) Fixtures (eg: outlets and switches) directly attached to aluminum wiring should be rated for it. The device will be stamped with "Al/Cu" or "CO/ALR". The latter supersedes the former, but both are completely safe. These fixtures are somewhat more expensive than the ordinary fixtures.
2) Wires should be properly connected (at least 3/4 way around the screw in a clockwise direction). All connections should be tight. While repeated tightening of the screws can make the problem worse, during the inspection it would pay off to snug up each connection.
{Note that stranded aluminum wiring is still often used for the main service entrance cable at your main panel. It should also be inspected.}
3) The "push-in" terminals are an extreme hazard with an aluminum wires. Any connections using the push-in terminals should be upgraded with the proper screw connections immediately.
4) There should be no signs of overheating: darkened connections, melted insulation, or "baked" fixtures. Any such damage should be repaired by a licensed Electrician and the connection should be upgraded.
5) Connections between aluminum and copper wire need to be handled specially. Current codes require that the connectors used must be specially marked for connecting aluminum to copper. The NEC requires that the wire be connected together using special crimp devices, with an anti-oxidant grease. The tools and materials for the latter are quite expensive - not practical to do it yourself unless you can rent the tool.
{Note that regulations are changing rapidly in this area. Suggest that you discuss any work with an Electrical inspector if you're going to do more than one or two connections.}
6) Any non-rated receptacles can be connected to aluminum wiring by means of a short copper "pigtail". See #5 above.
7) Shows reasonable workmanship: neat wiring, properly stripped (not nicked) wire etc.
If, when considering purchasing a home, my inspection of the exposed wiring (in your prospective home) shows no problems, you can consider the wiring safe. If there are signs of electrical problems in many places (which will be noted on your home inspection report), I suggest you consider a complete electrical inspection and possibly upgrading all branch wiring throughout the house. If the wrong receptacles are used, you can replace them with the proper type, or have the Electrician use pigtails. Having this professionally done by a licensed Electrician can run close to $10.00 per receptacle/switch plus hourly labor.
Dora,
I'm glad I could be of service to you and your clients.
David - Thanks for the article. We hired an electrician to come in and rewire and upgrade almost the entire house we purchased. We, as the home buyers thought it was a HUGE deal, but the electrician made sure to explain to us that at the time the house was built, everything was up to code; we're just smarter about things now and that's why we do have new codes. And really, the expense wasn't all that bad in the scheme of things - not at all what we expected it to be.
Jackie
David
Very good article on aluminum lower branch wiring. The picture of the melted insulators illustrates why this is so important. (resistance = heat = potential for fire) Keep up the good work!
Harold stated...
The problem is a concern with lower branch aluminum wiring, which is a solid conductor. This is used mostly for lights and outlets.(120 VAC)
For the main service entrance conductor, stranded aluminum is used. And yes an anti oxidant is used at the connections to prevent corrosion. Stranded aluminum does not suffer the same problems with expansion and contraction that would lead to loose connections found in a solid conductor.
Not to try to add confusion, but there are also some 240 VAC stranded aluminum service conductors (like that for an Oven/Range circuit, or an electric furnace) Being stranded these also are not that much of a concern.
Thank you, you are absolutely correct.
Service entry cables are stranded and do not pose a hazard as much as solid branch wiring does, as shown in my first picture.
David, Great post! Good education for people about a not so uncommon problem.
I am wondering if you really mean to say at the very end: "If, when considering purchasing a home, my inspection of the exposed wiring (in your prospective home) shows no problems, you can consider the wiring safe."? Do you really take off the covers of each electrical outlet and inspect inside? If you are only looking at the exposed wiring, I don't see how you can say it is safe if you have aluminum branch wiring involved. Every single outlet, switch, light fixture, etc. has to be exposed and inspected before you can say it is safe.
Also, in that same paragraph you say that the repairs can be made by the home owner, which is true, but as a home inspector I would never encourage the home owner to do it his or herself. In my view, the liability is skyhigh because, while you can describe perfectly how to do it, the homeowner can make mistakes and you will be legally "thought of" in the aftermath of a fire. Better to be on record encouraging the work to be done by a licensed contractor and let the homeowner take the chance on his own initiative.
Don't get me wrong, I like what you are doing with this post, but I think that added caution is necessary.
Bill,
My statement "If, when considering purchasing a home, my inspection of the exposed wiring (in your prospective home) shows no problems, you can consider the wiring safe."?" simply implies that if I performed the home inspection and my report states that there are no visible defects with the branch wiring (which aluminum wiring will absolutely be noted as a defect and needs to be corrected by an Electrician), then the existing visible wiring can be considered safe.
Why wouldn't it be? I opened the main SE panel, I inspected the operation of the receptacles for grounds / reversed polarity, etc...and inspected the type of wiring at the panel entry. My inspection of the Electrical system is thorough enough to determine if an Electrician is needed to correct any obvious issues.
David,
I wasn't meaning to question any of your inspection techniques or thoroughness. I just saying that with aluminum wiring, unless you have a signed document by a certified electrician that all the repairs have been made, you can't say that the branch circuit aluminum wiring is safe.
Visual inspection is not adequate with aluminum wiring. The fact that you don't have smoke coming out of the main panel, and there are no indications of excess heat on the wires at the breakers or with any of the exposed wiring, doesn't indicate that you don't have a pending melt down somewhere else in the house that you can't see.
The second important reason why a visual inspecion is no help when it comes to aluminum wiring is that the system can be perfectly safe for many years with the useage patterns of the present owners. Move a new family into the house and they will have different amperage needs off of different receptacles. These new usage patterns may uncover new weak points in the system.
As you said, it absolutely has to be noted as a defect every time.
Bill,
When I state...
If, when considering purchasing a home, my inspection of the exposed wiring (in your prospective home) shows no problems, you can consider the wiring safe.
I'm not referring to aluminum wiring at all. I'm referring to the existing house wiring which will be copper branch wiring.
As I stated...Aluminum wiring will absolutely be noted as a defect and needs to be corrected by an Electrician
I guess I got confused by the way you had that last paragraph set up. I'm with you now. Thanks for your patience.
No, thank you for understanding.
Due to your questioning on this topic, I think I'll revise the wording on that partcular sentence.