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Old 02-17-2017, 09:23 AM   #1
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Circuit breaker question


I'm installing a 100 amp sub panel to feed some additional circuits. This panel will only feed 120v circuits. My question is, can I use one side of a double pole 100 amp circuit breaker to feed the sub panel from the main panel?

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Old 02-17-2017, 09:34 AM   #2
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Re: Circuit breaker question


Even with only 120 loads you can still use both legs to feed the panel. You can probably use a smaller feed if you run 2 hots.

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Old 02-17-2017, 09:36 AM   #3
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Re: Circuit breaker question


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Even with only 120 loads you can still use both legs to feed the panel. You can probably use a smaller feed if you run 2 hots.
Thanks for the reply Jim, but can I do as I mentioned and run off of just one side of the breaker?
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Old 02-17-2017, 09:39 AM   #4
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Re: Circuit breaker question


Only one half of the slots will work... Which begs the question, are you also planning to place a jumper wire from one leg to the other or double up wires somehow? (So both legs will work.)

So far as I know, that would not be allowed. And in my opinion you should do it right or not at all.
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Old 02-17-2017, 09:57 AM   #5
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Re: Circuit breaker question


Why would you even consider this ? The cost of one additional conductor can not be that prohibitive.

Please explain your reasoning.
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Old 02-17-2017, 10:10 AM   #6
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Re: Circuit breaker question


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Why would you even consider this ? The cost of one additional conductor can not be that prohibitive.

Please explain your reasoning.
The cost might be able to be offset by running smaller conductors and conduit. The plan certainly is not the best way to add a panel. Perhaps the OP thinks if 120/240 is run they need 240 loads.
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Old 02-17-2017, 10:43 AM   #7
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Re: Circuit breaker question


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Why would you even consider this ? The cost of one additional conductor can not be that prohibitive.

Please explain your reasoning.
My primary reason for this question is to not have to use that much larger conduit for the extra 1ga line. Not sure I can get all the conductors in 1 inch conduit and not have a heating problem.
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Old 02-17-2017, 10:59 AM   #8
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Re: Circuit breaker question


Using both legs of a 50 amp breaker carries the same power as using one leg of a 100 amp breaker.

You wouldn't be on "1 ga".
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Old 02-17-2017, 12:07 PM   #9
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Re: Circuit breaker question


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My primary reason for this question is to not have to use that much larger conduit for the extra 1ga line. Not sure I can get all the conductors in 1 inch conduit and not have a heating problem.
A 50A 4-wire feeder fits fine in 1" conduit. I would not try to run a 100A 3-wire feeder in 1" conduit though. There is absolutely no reason to use a 120V-only feeder for this panel.
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