Aluminum and Copper Service Entrance Conductors (Mixed)

[Elect117]

I ran into a situation where the contractor ran aluminum for two phases (A&C) and copper for the other two (B & Neutral) in a 120/240V 3ph 4w set up.

The wire sizes were mis-match (Al larger than Cu) to accommodate the lower ampacity rating of the aluminum.

My gut said it was wrong since the wires would have different characteristics but I am having a hard time finding a code section that agrees. Is it actually not a code violation or issue?

P.S. I know it wouldn't be okay for parallel but that doesn't apply here.

 

[Little Bill]

Since the lugs in the equipment are rated for Cu and Al, I don't see a problem with it as long as neither touches the other.

 

[infinity]

No problem. Personally I wouldn't do it but the NEC doesn't care. Not that it matters but being that the B phase is a high leg it won't have any 120 volt loads.

 

[don_resqcapt19]

I ran into a situation where the contractor ran aluminum for two phases (A&C) and copper for the other two (B & Neutral) in a 120/240V 3ph 4w set up.

The wire sizes were mis-match (Al larger than Cu) to accommodate the lower ampacity rating of the aluminum.

My gut said it was wrong since the wires would have different characteristics but I am having a hard time finding a code section that agrees. Is it actually not a code violation or issue?

P.S. I know it wouldn't be okay for parallel but that doesn't apply here.

Actually it would be ok for parallel runs. That rule only requires that all of the conductors for one phase be identical. It is not required the conductors for A phase to be identical with the conductors for B, C or N.

 

[Elect117]

Actually it would be ok for parallel runs. That rule only requires that all of the conductors for one phase be identical. It is not required the conductors for A phase to be identical with the conductors for B, C or N.

Good to know.

I appreciate everyone's responses.

Thank you.