Using 1 leg of 3p brkr

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SiddMartin

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Have a spare 3p brkr 480v in existing panel, I want to use 2 poles for 1 ckt (480v) and the other pole for 2nd ckt (277v). Can't think of a code vio, only inconvience if either ckt would trip causing the other ckt to lose pwr as well.

any issues?
 
This is from the UL White Book, page 12 of the the:
Marking Guide
Molded Case Circuit Breakers


"
34.
3-Pole ? 1-Phase Rated ? ​
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3?pole circuit breakers are suitable for use on 3-phase systems only, unless marked to indicate use on 1-phase systems, such as, ?For 1?phase connections, use two outside poles,? or an equivalent statement. A 3-pole breaker used in place of a 2-pole breaker on a 3-phase system, such as a 2-pole breaker used in a branch
circuit that is actually two legs of a 3-phase system, is acceptable without the 3-pole breaker being specifically marked."


Sid,
I hope this helps.​

 
3?pole circuit breakers are suitable for use on 3-phase systems only, unless marked to indicate use on 1-phase systems, such as, ?For 1?phase connections, use two outside poles,? or an equivalent statement.

A 3-pole breaker used in place of a 2-pole breaker on a 3-phase system, such as a 2-pole breaker used in a branch circuit that is actually two legs of a 3-phase system, is acceptable without the 3-pole breaker being specifically marked."

Seems the second sentence says the opposite of the first sentence; what am I missing?
 
Team-MEI said:
Seems the second sentence says the opposite of the first sentence; what am I missing?
Click to expand...

The first sentence says you can not connect a 3 phase breaker to a single phase source.

The second sentence says you may connect a single phase load to a 3 phase breaker.
 
Team-MEI said:
3?pole circuit breakers are suitable for use on 3-phase systems only, unless marked to indicate use on 1-phase systems, such as, ?For 1?phase connections, use two outside poles,? or an equivalent statement.
Click to expand...
You'd never want to do that with a MWBC. That would place both hots on the same phase.
 
SiddMartin said:
Have a spare 3p brkr 480v in existing panel, I want to use 2 poles for 1 ckt (480v) and the other pole for 2nd ckt (277v). Can't think of a code vio, only inconvience if either ckt would trip causing the other ckt to lose pwr as well.

any issues?
Click to expand...

Is there even a neutral available for the 277V circuit? Many 480V panels don't supply neutrals
 
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Think legal but really bad idea. It will be a problem later for someone. If they understand and saying yes to save money then be sure to get a letter signed by owner so this does not come back to bite you. Yes safe but might not end up as smart way to go.
 
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