3 phase breaker for single phase load

[rayertz]

We have a control panel that has a 3 phase main breaker E104DISC (note the attached drawing).

As you can see the drawing calls for a single phase 480 vac feed. There is a jumper between the line side C phase down to the load side B phase thus making all phase utilized. The installing contractor pulled a 3 phase 480 feeder in lieu of single phase 480 vac and did not know what to do when he noticed the jumper. Plant engineering reviewed it and suggested to remove the jumper and land a three phases.

Now a plant inspector is reviewing the installation and is raising a concern that using a 3 phase breaker to feed a single phase load may be a code issue.

Please advise with your expert comments if this is an issue.

Thanks

 

[infinity]

Since the jumper is part of the factory wiring of the equipment I would not remove it and would supply it as designed with 1Ø. Just use two of the three legs that the contractor ran for your 1Ø, 480 and safe off the third one. The NEC doesn't have an issue with using a 3 pole CB and only using two poles for 1Ø.

 

[templdl]

We have a control panel that has a 3 phase main breaker E104DISC (note the attached drawing).

As you can see the drawing calls for a single phase 480 vac feed. There is a jumper between the line side C phase down to the load side B phase thus making all phase utilized. The installing contractor pulled a 3 phase 480 feeder in lieu of single phase 480 vac and did not know what to do when he noticed the jumper. Plant engineering reviewed it and suggested to remove the jumper and land a three phases.

Now a plant inspector is reviewing the installation and is raising a concern that using a 3 phase breaker to feed a single phase load may be a code issue.

Please advise with your expert comments if this is an issue.

Thanks

I'm not familiar with the breaker but simply feeding (2)poles of a (3) pole breaker and taking one pole from the load side of the breaker back to the remaining open line side is certainly not an issue at all. If it is already installed that way simply leave it. The only reason that I can think of where it may be necessary is if the beaker has an electronic trip that would sense a loss of phase or if it has GF sensing which may result in a nuisance trip be cause the breaker needs that 3rd pole to be energized. By omitting thar 3rd pole you could mess with its brains. But other than that a simple TM breaker will work just fine with (2) lines in and (2) lines out , usually using the outside poles, leaving the 3rd center pole with no connections.

 

[kwired]

Agree, you usually only see this with motor overload units that have phase loss protection. If the breaker has any kind of phase loss protection it will be necessary to do this otherwise just using two poles will work fine.

 

[L8TRG8TR]

Besides most three pole breakers say right on them for single phase you can use any two poles


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