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1/0 AL to 12NM splice


John Dirks Jr
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The pictures show a splice in the main panel of 12NM to 1/0AL. The 1/0 AL then runs to a box on the air handler where it changes back to 12NM to feed power to the blower.

Sparky is coming out for other reasons so I'll put a note in there for him to check this too. Meanwhile, help educate me. Is there anything specific that I should say is wrong with this arrangement?

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The pictures show a splice in the main panel of 12NM to 1/0AL. The 1/0 AL then runs to a box on the air handler where it changes back to 12NM to feed power to the blower.

Sparky is coming out for other reasons so I'll put a note in there for him to check this too. Meanwhile, help educate me. Is there anything specific that I should say is wrong with this arrangement?

Well, for starters, the connection between the grounding wires is entirely inadequate.

I can't see through the tape at the other connections but it looks like they might have used split bolts. Those are OK to connect copper to aluminum, but I don't know of any split bolt that will accept both a #12 wire and a #1/0 wire. The size difference is just too great.

- Jim Katen, Oregon

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Jim will correct me if I am wrong, but you can't go from a smaller size wire to a larger size. You can go from big to little, but not vice versa.

He hasn't come back so you must be correct.

This place had two panels, each with its own SEC from the meter. I couldn't get the cover off the panel on the left since some brilliant shmuck framed the opening to block the panel cover screws.

Thanks for the help everyone.

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I couldn't get the cover off the panel on the left since some brilliant shmuck framed the opening to block the panel cover screws.

I can't tell you how many times I've told people that I need full access to the panel to pull the cover off, only to find they made just enough room to open the door. I think people don't realize those dead fronts actually come off......

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Jim will correct me if I am wrong, but you can't go from a smaller size wire to a larger size. You can go from big to little, but not vice versa.

I can't find anything that would prohibit changing wire sizes in either direction as long as the wires are rated for the ampacity and the overcurrent protection is adequate for all the sizes. For a big jump in size, you'd have to make the connection in several steps.

- Jim Katen, Oregon

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I can't find anything that would prohibit changing wire sizes in either direction as long as the wires are rated for the ampacity and the overcurrent protection is adequate for all the sizes.

I swear I've read somewhere that for long runs of wire, you can run say a 15 amp circuit with 12 gauge wire stepped down to 14 gauge wire (for voltage loss), but not the other way around. Now I need to find out where I read that.

I guess I need to invest in a copy of the current NEC and study up on it.

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