Copper (Was: 10 forgotten wonders of 1980s homes

Paul Koning paulkoning at
Thu Dec 31 13:59:26 CST 2015

> On Dec 31, 2015, at 2:47 PM, Geoffrey Oltmans <oltmansg at> wrote:
> On Thu, Dec 31, 2015 at 12:17 PM, Fred Cisin <cisin at> wrote:
>> Almost half a century ago, there were attempts to use aluminium instead of
>> copper for house wiring.  It did not go well.
> No, it didn't! We looked at several old houses back in 2012 before we
> bought the house we're in now. Several of these houses were from the late
> 60's/early 70's and that concern was forefront in my mind with them. They
> still sell special outlets and switches compatible with aluminum wiring in
> the hardware stores.

I haven't see aluminum-rated devices in hardware stores in many years.  Be careful: typically they will be labeled either as "copper only" or as "CU/AL".  But that doesn't mean "copper or aluminum" -- it means you're allowed to user copper-clad aluminum.  That's a hack type of wire that was adopted for a while after the plain aluminum was discovered to be a Very Bad Idea.  It's not quite as bad but there is really no justification for its existence, and indeed it is no longer the current practice.  Copper-clad aluminum can be used with copper without much trouble, but the wire is thicker and it breaks more easily.

Plain aluminum must only be used with devices specifically rated for plain aluminum.  You may need to use anti-corrosion paste.  "devices" includes wire nuts -- standard copper-only wire nuts are not approved for use with aluminum wire.

My experience is that aluminum-rated devices and wire nuts can only be found at electric supply specialists, and they are vastly more expensive than regular devices.  When I used up my box of aluminum-rated wire nuts (standard hardware store item in 1980) I found that trying to buy them now (2005 or so) was possible but I'd have to pay a dollar EACH, if not more.

The only place where you're likely still to find aluminum-rated devices without a lot of effort is in high current stuff -- main breakers, 100 amp branch breakers, that sort of thing -- because aluminum cable is still used there at least by some people.  Personally, I never use it; 2 gauge copper may cost more but I prefer the peace of mind it delivers.


More information about the cctalk mailing list