#6 aluminum wire, 50 amp breakers?

[voight]

I am seeing quite a few 50 amp breakers with #6 aluminum wire connected to the breakers. I know this is not acceptable using current electrical standards. I would like some opinions on how you guys deal with this on older homes.

Dave Voight

Honest Home Inspections

[Chad Fabry]

The wire that's feeding(or that's fed by) the 50 amp breaker is too small. The 6 gauge aluminum wire is rated for 40 amps. An electrician should evaluate and recommend repair which may include either running a #6 copper conductor, a #4 aluminum conductor or, depending on the circuit load, may be as simple as replacing the 50 amp breaker with a 40 amp breaker.

I guess I'd write something like that and put in some boiler about how a circuit can overheat when overloaded.

[Jim Katen]

Originally posted by voight

I am seeing quite a few 50 amp breakers with #6 aluminum wire connected to the breakers. I know this is not acceptable using current electrical standards. I would like some opinions on how you guys deal with this on older homes.

Dave Voight

Honest Home Inspections

Dave,

It might not be unacceptable. The NEC isn't as cut & dry as we home inspectors might like.

If a few conditions are met, you might be able to apply the 75-degree column from Table 310-16 in which case the #6 aluminum wire can safely serve a 50-amp circuit.

First of all, if it's a motor circuit like a well pump or AC unit, it's probably fine.

Second, if the aluminum cable is Romex (NM), you can't use the 75-degree column. You must use the 60-degree column. In this case, the breaker would be too large. (Or the cable too small.)

However *if* it's an SE cable and *if* the breaker is dual rated for 60/75-degrees and *if* the equipment terminations are dual rated at 60/75-degrees, then it's probably ok. (I've noticed that most equipment terminals have been dual rated for the past 10-15 years.)

All this is in 110-14©(1).

So, if you really want to make a determination about proper ampacity in the field, start taking apart those equipment terminations and get out your magnifying glass to read the temperature ratings on them. Also, if you really, really want to go by the book, don't forget to derate the conductors if they go through a hot attic.

Personally (and I'm not recommending you do this, it's just what I do) if I see SE cable, I use the 75-degree ratings. If I see NM cable, I use the 60-degree ratings.

And frankly, when you get right down to it, 10 extra amps on a #6 aluminum wire isn't going to make it warm let alone start any fires.

- Jim Katen, Oregon

[Bruce Thomas]

Some times when I read these posts I say to myself, why didn't I know that. I guess that's why I still read them.

Thanks Jim!!

Bruce