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Thursday, May 6, 2021

Question:

Hello,

On a commercial service a contractor removed a de-rated aluminum neutral and replaced it with copper THHN of proper size. That made the hot legs, aluminum, and the neutral, copper, in a pipe mast. Is this allowed in the NEC? The local utility has said that they would not hook it up like this. I'm wondering if it would be allowed in a different situation.

Thanks,

Adam Rumpf

A

Answer:

Hi Adam,

In most areas electrical installations at the service must not only meet the requirements of the NEC, but there may be utility company service requirements. The NEC would not restrict the neutral service conductor from being copper while the other service conductors are aluminum. You mentioned THHN insulation which is suitable for being installed in dry locations. Unless the insulation has a rating of something such as THHN/THWN, the installation would be a violation if in a wet location. See NEC 310.10.

Hope this is helpful.

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