Alum-Copper connection

[BlackJack]

Alum Service Ent. Conductor. At the input lugs showing minimal signs of discoloration / corrision. No Penetrox that I could see. Double and tripple wire connections on Netural and GND. 1 netural connected to Gnd, and 1 GND connected to Netural. 1995 vintage home.

Air Cond #2 Breaker tripped.

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[homnspector]

I often see service conductors without anti corrosive. Power company here says it is "not necessary". BTW, what size is the main breaker?

Never mind, I see that it is 150 amp. That seems like a lot of circuits for 150 amp.

[hausdok]

Hi,

It's "new" aluminum wire. As long as the lugs are compatible there shouldn't be a problem. Lots of folks are still applying the anti-oxidation paste to everything aluminum, but I'm not convinced that with the new aluminum alloys it's absolutely necessary, 'cuz I've never seen a single instance where it was a problem at those main lugs.

ONE TEAM - ONE FIGHT!!!

Mike

[Terence McCann]

Mike:

Do you know approximately what year they came out with "new" aluminum?

Thanks.

[hausdok]

Hi,

According to Hansen's book, the wiring industry first began experimenting with new alloys around 1972 and these weren't as trouble prone. By 1979 the aluminum industry had adopted higher standards and in 1981 the NEC began requiring special allows be used in aluminum wiring and must be at least an AA8000 alloy.

As far as the paste, Hansen says, "While the NEC does not specifically require anti-oxidant, it is a good idea for all aluminum wire connections to breakers. The NEC does require that it be applied neatly, and there should be no excess paste inside the panel."

ONE TEAM - ONE FIGHT!!!

Mike

[Jim Katen]

If you're going to call out missing paste, the only NEC reference will be 110.3(B). It's the one that says the panel has to be installed in accordance with its listing and labeling instructions.

Panel manufacturers used to require the paste on aluminum connections. I'm not so sure that they still do. It certainly isn't mentioned on the label that's stuck to the panel, though it might be buried in the UL listing.

Like the others, I've never seen a problem due to its omission.

My personal opinion is that it's a "best practice" but not a big deal if missing.

- Jim Katen, Oregon

[Trailblazer]

The newer alloys are definetly better. However, cold flow over time can be a problem. All conductor termininations should be torqued to specifications whenever you access them, especially aluminum. The loose connections overheat and affect breaker operation as well as isulation.

[hausdok]

Hi Trailblazer,

That's all well and good but we don't torque anything to do what we do, so I'm not sure I understand what your point is. How does knowing this help an inspector?

ONE TEAM - ONE FIGHT!!!

Mike

[Jim Katen]

Originally posted by Trailblazer

The newer alloys are definetly better. However, cold flow over time can be a problem. All conductor termininations should be torqued to specifications whenever you access them, especially aluminum. The loose connections overheat and affect breaker operation as well as isulation.

Just to be clear, I'm sure that when you say, "whenever you access them" that you aren't referring to home inspectors. I'd hate for a home inspector to read this thread and think that he ought to be torquing electrical connections.

Also, as I'm sure you're aware, there's a danger that by overtorquing aluminum connections you can cut right through the wire over time, especially on residential equipment.

I know it's commonly done in industrial settings, but how many residential electricians do you know who carry torque screwdrivers? I've never met one.

Without a torque screwdriver, repeatedly tightening an aluminum connection is a dangerous practice.

- Jim Katen, Oregon