Question regarding copper & aluminum wiring?

Question

Okay, so aluminum wires oxidizes when exposed to air long enough, and the alumina oxide is highly resistive- so connections to terminals on switches are prone to heating up and melting. This effect is compounded when accelerated by copper and aluminum conductors being mated.

But how come on service panels- the bus bar, and wire lugs are all aluminum, and you s***w the copper leads right into those with no worry?

Answer 1

Previous poster has an excellent answer. I would only add that the reason there is a better mechanical connection is also due to teh softness of the aluminium

Answer 2

The bus bar bars and lugs are not aluminium  they are Copper  are and the copper is is treated, similar to the old VIR cables that used to be tinned,  when they did away with VIR cables and changed to PVC cables they still tinned the copper conductors for a while before it dawned on some on it was a waste of time doing that with PVC insulation.

Brass reacts with with aluminium so that when you gland aluminium cable you have to use aluminium glands and bannjo`s,  Aluminium cables are hardly used now although you get aluminium armoured with copper cables is used a lot with large as it is lighter than steel wired armoured to install.

Answer 3

The screws that hold the wires into the bus bar make an excellent mechanical connection that is almost vibration & thermal expansion-proof.  The set screws are specially designed to dig into the metal to make a long-lasting electrical connection that resists oxidation.

Its the copper to aluminum wire connectors and the outlets that have aluminum wire plugged in, or screwed on that you have to worry about.

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Answer 4

You've only stated part of the problem.

Aluminum is also more susceptible to 'thermal creep',

in which heat/cool, expansion/contraction cycles 'work'

the connection loose.

Special lugs & connectors rated for 'aluminum and

copper clad Al. conductors' + the use of antioxidant

compounds have largely solved the problem.

The lugs in question are so marked and are

designed to maintain the proper pressure.