Using a 3 pole circuit breaker with 2 wires

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Old 02-20-14, 06:35 AM
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Using a 3 pole circuit breaker with 2 wires

I have an enclosure with a 3 pole breaker but my house only has 2 hot wires, can I use the circuit breaker safely without any harm?
 
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Old 02-20-14, 07:05 AM
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It will work well using the 3 pole (triple wide triple) breaker for a 2 hot plus neutral 120/240 volt circuit or even a one hot plus neutral 120 volt circuit.

Most likely the enclosure was or is for a 3 phase electrical system but you can use the phases individually (provided you have a neutral) or two at a time (for 240 or 208 volts depending on the system).

The disadvantage of using one 3 pole breaker instead of 3 single pole breakers is that if one circuit should trip its breaker, up to 2 other circuits (sharing the breaker set) will be flipped off too.

Be sure you have a neutral in the box before connecting up a 120 volt circuit. You may not use ground in lieu of neutral. Also measure the voltage between the chosen breaker terminal and neutral before connecting it up. In some 3 phase systems (240 volt delta) one pole will measure 208 volts to neutral and you never want to use that pole all by itself.
 
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Old 02-20-14, 07:19 AM
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I have an enclosure with a 3 pole breaker but my house only has 2 hot wires, can I use the circuit breaker safely without any harm?
Where are you wanting to use the 3 pole breaker, will this be your main service disconnect? Does the enclosure have a neutral bar?
 
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Old 02-20-14, 08:37 AM
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Yes, I want to use it as a main service disconnect. Yes there is a neutral bar.
 
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Old 02-20-14, 09:17 AM
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Using a 3 phase panel will also have 1/3 of the panel spaces dead.
 
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Old 02-20-14, 09:33 AM
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I forgot to ask in my last post, when connecting, should I connect the neutral first?
 
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Old 02-20-14, 09:44 AM
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All work should be done with the panel off.

Many like to cut-in a panel doing grounds first, neutrals and then the hots out of practice.
 
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Old 02-20-14, 06:58 PM
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Yes, I want to use it as a main service disconnect. Yes there is a neutral bar.
Is it service entrance rated? It needs to be.

zizanio
I forgot to ask in my last post, when connecting, should I connect the neutral first?
It shouldn't make any difference because the meter should be pulled or the service disconnected by the power company and everything should be dead.
 
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Old 02-21-14, 12:03 PM
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Thank you everyone for your help. One last question. Is there a distance limit from the service entrance? Does it have to be within 5 feet or 10 feet?
 
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Old 02-21-14, 12:26 PM
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The NEC requires the unfused conductors to be "as short as practical". No actual distance is specified. This is up to the inspector.
 
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