I am running a 200 amp feeder approx 80' long in 2" EMT. I very rarely use aluminum wire, however with the price of copper skyrocketing I've decided to do so in this situation.

My question is about the equipment ground in the EMT. I would rather run my EG in copper and the hots and neutral in aluminum. I can see no reason why this would be a problem but was wondering if it a poor trade practice for any reason? I guess I would rather use copper when making up ground lugs etc.

Also, how many guys are using aluminum more and what do you think of it. A rep from the aluminum industry was doing some demonstrations in a supply house recently and had some pretty convincing arguments for using aluminum. He showed how the old aluminum conductors were much easier to break after a few bends of the wire and stated that nowhere in the code is the use of deox required. I will still use it though to sleep beter.

No code reason not to mix conductor types.

That said....

If I come across an installation that has mixed conductors I assume someone was using scraps saving a buck etc.

I also generally install copper but would have no problem using an AL EGC with AL circuit conductors.

As far as 'deox' the sales rep is correct, not an NEC requirment. Go ahead and use it if you like. IMO it is of little value.

It comes reinstalled in some crimp connectors my guess it works as both a lube while crushing and keeps water from entering the connector.



[This message has been edited by iwire (edited 05-31-2006).]

Bob,
Why do you say that it is of little value?
Don

I like to work with aluminum wiring for larger cables... It is a little less expensive (especially with the current escalation of copper prices)... It is easier to handle for most applications...

I always use NoAlox or Penetrox when doing my connections, seems to me to just be good practice for a few pennies per connection.

I only use it for large feeder connections like sub panels and such. Wouldn't use it for branch circuits... not because I see anything wrong with it, but I wouldn't want the potential of a home owner playing with connections in aluminum down the road.

IMHO there is nothing wrong with Aluminum for these larger applications.

Glen

Don


I have never seen any documentation that it can do anything. I consider it a snake oil item.

It makes us feel we are going that extra step of craftsmanship without knowing if it does anything.

Other than possible moisture displacement what can it really do to improve a connection?

JMO, Bob

Make life easy use 2-1/2" also consider a mogal fitting.

[This message has been edited by LK (edited 05-31-2006).]

I don't think I have ever seen anti-oxidant compound used in accordance with the manufacturer's instructions, which typically require the use of a wire brush.

Good issue, not code, but manufactures requirement.

Lee:
I've been using Al IF it's in the spec, & occasionally for budget reasons. 750kcmil, down to 4/0. As to a ground conductor, Al is not a problem. Personally, I don't like to mix. I've seen #6 Al used for site lighting; had I issue where a 'nick' caused a leg failure in the pipe; not the fault of the conductor material though.

Bob & Don:
As to pentrox (etc) I've been using it for 30+ years! It's what my 'teachers' did, & old habits are hard to break.

John

Live near an ocean and one would sing a different tune about no-ox.... Without it AL turns into a block of chalk over time. So much so that all the over-head drop lines here near the beach are copper. Medium voltage too.

It cant hurt..... But I do all the time.

Ryan says, and I agree..

"I don't think I have ever seen anti-oxidant compound used in accordance with the manufacturer's instructions, which typically require the use of a wire brush."

But, I always put the anti-oxidant on a tooth brush sized wire brush (scratch brush) and work it into the conductors. It breaks the oxidation layer and works the compound into the individual strands.
Whether or not it helps I don't know (I believe it does), but I've seen several failures at meter sockets where a small dab of no-alox was just squeezed onto the conductor without spreading it.
It takes less than 30 seconds for each wire and seems to result in a "better job".

Bob,
Aluminum oxide is an insulator and forms almost instinctually when bare aluminum is exposed to air. The use of an anti-oxidant prevents the oxide from forming if correctly done. In many cases this required the use of a wire brush to remove the aluminum oxide after the anti-oxidant is applied to the wire. The other thing that helps is that the aluminum oxide is very brittle and the normal installation practices should shatter the oxide providing a bare connection, but if the termination is not "gas tight" the oxide will soon reform and may result in a failed connection. This brittleness is the basis for the use of pre-filled connectors. The crimping action will break the oxide and the anti-oxidant will prevent it from reforming. If you are sure that your connection will remain 100% gas tight, then there is no need for the anti-oxidant.
Don

quote"Live near an ocean and one would sing a different tune about no-ox.... Without it AL turns into a block of chalk over time."

Yep, I agree whole heartedly. The windward sides of the Island I live on get salt air that is like fog some days. It does havoc on terminations that have no antioxidant, or at least no recent applications of anti oxidant. Aluminimum screen frames are equally subjected to the yellow grundge oxidation factor.

Don, the same could also be said for copper to a FAR LESSER degree. Lesser to the point that only extreme cases are even recognized. Green/white patina copper oxidization is equally bad.

Even though not "required" on AL, failure to do so here will raise some eye-brows with Inspectors here. Call it workmanship.... If it is "snake-oil", it keeps Inspectors out of my hair....

e57,
Copper oxide is conductive, aluminum oxide is an insulator.
Don

Note bold "Far Lesser", and "to the point that only extreme cases are even recognized." Think about it the next time you need to make a scratch to test for voltage. Apparently copper oxide films were one of the first noted semi-conductors..... Anyway, point was oxidation = bad.

We're starting to use Al more and more on services and sub-panels, with the increasing price of copper. We always use Penetrox, yet the Poco here NEVER uses any Penetrox on their aluminum conductors...even the ones they terminate in meters for underground services.

For larger feeders and services, we always use al unless spec for cpr. Not a problem if installed correctly. As for noalox, always use it on the conductor and the termination threads.