Thread: Aluminum - antioxidant coating

Do aluminum service and branch circuit conductors require an anti-oxidant coating at circuit breaker connections?

If yes, where in code is it called for and if known, when did it take effect?

Thanks

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I don't think there were any 'requirements' to use anti-oxidant on circuit breaker or any other terminals rated for aluminum wire connections in any edition of the NEC. I'm not sure about prior to 1975 .. Rather the NEC defers to manufacturers for requirements of their devices equipment, wire, etc.. as outlined in NEC 110.3 a and b

Generally instructions to do not accompany wire. However devices or equipment will often come with instructions that list termination recomendations or possible requirements for aluminum wire.

An example of what it will say with instructions accompanying a packaged circuit breaker ... this is from cutler hammer CH250 circuit breaker instructions

" When aluminum conductors are used the application of a suitable anti oxidant joint compound is recommended to reduce the possibility of terminal overheating."

Notice even here it is a recommendation not a requirement.

However this is usually preceded by the word "CAUTION" ...I usually take this to mean you are much better off using it.....

UL 486E I believe is the document we need for circuit breakers. Can't find a link to it.

I did find a related link in UL 486A and 486B " Connection Procedure Requirements" for connectors This document does not cover ' wire binding screws ' . Wire binding screws are those like you see on receptacles and switches where you bend the wire around and under the screw head.

In specific UL486 A 10.15 (d) Preliminary Preparation of Conductor Required

Text copy below

UL 486A/486B a-d
Connection Procedure Requirement

d) PRELIMINARY PREPARATION OF CONDUCTOR REQUIRED –Instructions for preparation of the conductors, such as use of compound or twisting conductors together before assembly, shall appear on the unit container or an information sheet packed in the unit container.

UL comment section for terminations for 'connectors'

Connection Rules

No such thing as a “general rule”
Oxide inhibitor
Wire brushing
Crimp methods
Follow the manufacturer’s instructions!

Hope this helps