Of mains distribution and aluminum wire

[iXod]

It has been well-known for decades that aluminum wire needs to be prepared and used only with approved cu/al components to avoid oxidation and Big Trouble.

But I note that many components are aluminum and accept copper wire without any preparation.

What is it about the aluminum used in components that means the installer doesn't have to use anti-oxidant goo when using copper wire?

Thanks.

[David Hess]

The aluminum is plated with another solder friendly metal like copper, tin, or nickel.

[coppercone2]

family friends shed almost/kinda caught on fire because of Aluminum wire. be careful.

imo not worth it. copper is still kinda janky

[rhb]

Part of the issue with aluminum wire is creep.  This proved excessive in end use applications.  And aluminum in contact with steel will corrode in a heartbeat in the presence of water which is an issue in humid climates. I suspect that abrasion of very thin plating on steel hardware was the biggest cause of fires.

Aluminum wire it widely used in heavy gauges.  I just used 3/0 for the feed to my shop.  It's a 165 ft run, so I needed a large conductor.  Nothing was applied to the wire or the connectors.  But the connectors are not bare steel.

I'm not aware of any issue with aluminum and copper in contact.  But long ago I slid a steel cam follower into a VW crankcase I had just cleaned with a pressure washer.  Within a few hours corrosion had practically welded it in place.  It took considerable pounding with a heavy brass pipe and large hammer to get the cam follower free.  I was impressed.

[rstofer]

Cold flow is the issue.  It is quite possible to make aluminum hard enough to prevent flow when we're talking about set-screw type terminals or bus bar.  It is not possible to make the wire that hard as you couldn't bend it during installation.  Aluminum bus bar has been the standard in unit substations for decades.  Copper is often available at significant additional extra expense.  The bus bar joints will be connected with standard hardware but with Belleville cupped washers to retain tension.

[rhb]

It is certainly a struggle to bend 3/0 Al wire.  I read the technical report on the country club fire, but it was so long ago I was not prepared to say creep was the dominant cause even though that was my recollection.

Standard practice for remediation of Al house wiring is to pigtail the aluminum with copper to the switch and receptacle terminals.  Apparently wire nuts don't have the creep issue when connecting the copper and aluminum wire.

[David Hess]

I have noticed that in areas were aluminum house wiring was used, the local hardware stores will carry aluminum wire compatible power switches and sockets (marked CO/ALR) which have some type of plating (indium?) on the terminals.

[tkamiya]

Aluminum wires problem was caused by several factors:

1)  Aluminum wires are rated LOWER than copper wires but electricians did not always treat it as such
2)  Aluminum wires have high resistance and thus prone to heat up when not correctly sized
3)  When aluminum wires and cu can be joined but without proper antioxidizing paste, electrolysis will promote corrosion

All that caused house fires.  But, there is nothing inherently wrong with aluminum wires.  The way it was applied caused problems.  I understand electricians were not properly educated when transitioning to aluminum wires happened.  So they just treated the same as copper. 

In fact, in typical house in US today use aluminum wires in certain places.  Mains feed to the house is usually aluminum.  Meter to the master breaker panels are usually aluminum.  In my house, feed to stove is aluminum as well.  But they are properly rated by today's standard and there are anti-corrosive paste applied at connection.  You can buy aluminum wires in home centers as well but not in small gauges.

[coppercone2]

what happens to the aluminum paste if you have some bullshit improper installation with water exposure, out door etc?'

do bugs eat the stuff?

[tkamiya]

Well, it all depends on what's wrong with the installation.

I've never heard of bugs eating paste.  But, for some reasons, rates and squirrels love to chew on insulation.  I've seen wires stripped and teeth marks on what's remaining.  Lose screws and wire nuts will cause localized heating.  Plastics around it can melt and char.  Wires can show signs of heating such as discolorations. 

Most common issues started when wires are connected with wire nuts.  It's worse when it's cu/al connection but it can happen with al/al.  Wire nuts heat up well beyond too hot to touch.  It can melt or burn.  If plastic completely melt away, it will usually end in short - then it will trip circuit breakers.  It's the most dangerous when this is incomplete.  Heat up without tripping or causing arc over.  Wire nuts for aluminum are usually colored in purple, I think.   It's gel filled for water resistance and corrosion inhibition.  You can google "aluminum wire electrical wire" and see images of how bad this can be.

[rstofer]

Aluminum wires problem was caused by several factors:

1)  Aluminum wires are rated LOWER than copper wires but electricians did not always treat it as such
2)  Aluminum wires have high resistance and thus prone to heat up when not correctly sized
3)  When aluminum wires and cu can be joined but without proper antioxidizing paste, electrolysis will promote corrosion

All that caused house fires.

I don't think any of those items were an issue in industrial environments.  What I think was the real problem with residential is the backwire push-in connections on receptacles or the non-clamping style screw connector - in other words, the cheap spec grade wiring devices.  The internal piece on the backwire device has a sharp edge to cut in to the copper wire and would eventually cut through the aluminum wire.  I never used aluminum for residential and, even in industrial, only for long runs of high current circuits where there was a demonstrable savings over copper wire.  The savings had to be huge because a) the wire had to be bigger, b) the conduit had to be bigger and c) we had to use crimp-on aluminum to copper fittings before terminating on a circuit breaker.  I would think about it for 400A circuits but probably nothing below that.  Maybe 225A but that's a stretch.

These days we have to use arc detecting circuit breakers on certain residential circuits.  I imagine this is an offshoot of aluminum wire.  I can't imagine anyone using aluminum wire for residential branch circuits but it might happen for larger panel feeders.

Aluminum continues to be the leading conductor for utilities and has been for more than 100 years.

https://en.wikipedia.org/wiki/Aluminum_building_wiring

[Kalin]

Here in Canada the cost savings are significant. Aluminum being 1/3 the price for 200A capable cable. So that tends to be my go to for that size upwards. Another thing that comes into play is the different rates of thermal expansion between copper and aluminum allowing space for a high resistance fault between wires twist together. I have never seen that myself but I know guys that have seen it and it can be dangerous.

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[soldar]

This page explains it: https://www.carsondunlop.com/training/resources/the-true-story-behind-aluminum-wiring-part-one/

Also https://en.wikipedia.org/wiki/Aluminum_building_wiring

[tkamiya]

I haven't heard of the problem in industrial or business setting either.  But in Florida and in many other parts of country, business are done differently from residential setups, for example, mandatory use of conduit.  Most electricians don't do buss bars either and they are usually aluminum.

I have seen so many improperly done copper to copper connections, too, and they were supposedly done by "professionals".  In that environment, if one introduces something slightly more complicated, it can go very very badly.