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Double Tap


Mike Lamb
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Is the question whether it's sometimes OK to double tap before the main service disconnect (assuming we're looking at a main disconnect)?

I thought those taps before the main were always a no-no because there would be no disconnect or overcurrent protection for whatever is downstream of the second taps. And someone might fatally assume that flipping the main disconnect had shut off everything in the house.

If I'm missing something, I'll just go back to lurking ... [;)]

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The manufacturer may allow it. Square D in this case. It would or should be printed on the side of the lug which is not easy to see. It should also tell what wire sizes that can be used. I agree that double tapping is not a good idea even if allowed.

These conductors run to a 100 amp disconnect.

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The manufacturer may allow it. Square D in this case. It would or should be printed on the side of the lug which is not easy to see. It should also tell what wire sizes that can be used. I agree that double tapping is not a good idea even if allowed.

These conductors run to a 100 amp disconnect.

If you could get the wires out of the way, the label should say.

On the other hand, I've never seen a small load center equipped with main lugs rated for more than one conductor. When they are, the hole in the lug is shaped sort of like a figure 8. See the attached pictures

Download Attachment: icon_photo.gif MultiWireLug1.JPG

190.38 KB

Download Attachment: icon_photo.gif MultiWireLug2a.JPG

216.35 KB.

- Jim Katen, Oregon

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I believe in any case where the lugs do allow 2 conductors, they still have to be the same size, no? You quite obviously have 2 different size conductors There, so it doesn't matter what the lugs are listed for, and as Jim said, doubtful they are listed for two wires anyway in that panel.

Typically anything that will allow two wires that are not of the same gauge will in some way resemble a split bolt, having two separated chambers that will adjust in size independently of the other.

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I believe in any case where the lugs do allow 2 conductors, they still have to be the same size, no? You quite obviously have 2 different size conductors There, so it doesn't matter what the lugs are listed for, and as Jim said, doubtful they are listed for two wires anyway in that panel.

Typically anything that will allow two wires that are not of the same gauge will in some way resemble a split bolt, having two separated chambers that will adjust in size independently of the other.

Actually, the lugs in the pictures that I posted are, indeed rated for two different size wires. They're rare birds though.

- Jim Katen, Oregon

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I believe in any case where the lugs do allow 2 conductors, they still have to be the same size, no? You quite obviously have 2 different size conductors There, so it doesn't matter what the lugs are listed for, and as Jim said, doubtful they are listed for two wires anyway in that panel.

Typically anything that will allow two wires that are not of the same gauge will in some way resemble a split bolt, having two separated chambers that will adjust in size independently of the other.

Actually, the lugs in the pictures that I posted are, indeed rated for two different size wires. They're rare birds though.

- Jim Katen, Oregon

How do those of us less gifted than you recognize these kinds of lugs? The notch?

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