Hi gang. There is a condo nearby (one of those old building in DC that was turned into condos in the 90’s) that I am interested in buying, but I noticed that a hefty aluminum wiring is used from a 100 amp breaker in the main panel to a small sub panel near the bathroom. All other branch circuits in the main panel are copper. Both ends are nicely terminated, clean and secure, and the job looks like it was done very recently (past year or two).
I always thought AL wiring was a no-no but from poking around on the internet, it seems to be allowed in service entrance runs and in short runs from main panels to sub panels, provided that (1) both ends are mechanically terminated (screwed down, no wire nuts) and (2) the panel lugs are rated for aluminum wire. Is this generally correct?
Having a background in electrical engineering I am aware of the potential issues with aluminum wiring to point-of-use terminations such as sockets and switches, and the risk of fire from high resistance junctions. I just don’t want to get all the way to almost closing and then have this pop up in the home inspection as a question mark.
for the short runs of service entrance and subpanels there are a minimal number of connections, the connection points will work with aluminum, likely would have been installed by a licensed electrician which makes it OK.
Generally, yes, that is correct. Aluminum is allowed under those conditions by the NEC. As johnpost said, though, make sure you check local codes since they may have more restrictions.
A lot of folks are recommending aluminum these days just because of the cost savings. Personally I don’t like aluminum, but generally speaking, it is allowed.
You may also want to check with whoever is going to provide insurance for the condo, since they may also have restrictions above and beyond what is according to code.
A lot of the problems with aluminum wiring in the 60’s/70’s were caused by interchaning copper and aluminum, using the same fittings, etc. Assuming a qualified electrician connected everything properly, you should be okay, but it’s worth having someone look at it.
Typically too, an anti-oxidization paste will be applied to the cable at the terminal. You may even be able to see signs of it; it’s usually bluish. Might even be required by code.
A Master Electrician taught me the rule for when to use copper, and when to use aluminum. The rule is ‘use copper’.
But this sounds like something done to code. As kunilou mentioned, the problems with aluminum were mostly due to improper installation. I’ve seen aluminum used for long runs of heavy guage wire, like for an electric stove, to save money. The great danger I’ve heard about is that a crack in the wire caused by a sharp bend can be unseen under the insulation, but a good way to start a fire.
a nick in a copper wire or too sharp a bend (even under insulation) will create a hot spot. i’ve seen charred, burnt to small diameter wires in copper too.