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Old 06-02-2013, 09:46 PM   #16
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Using 208v "B" phase in open delta?


If you have 240 volts phase to phase (120/240 volt 3 phase system) and you have 120 volts phase to neutral for two of the phases then you will have 208 volts phase to neutral for the third phase.

I would not rule out abnormal phase shifts resulting in high leg to neutral of something other than 208 volts but if this were to occur (perhaps more likely on an open delta system) then some changes to other voltage relationships willl also occur simultaneously.

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Old 06-04-2013, 06:15 AM   #17
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Using 208v "B" phase in open delta?


My electrician basically confirmed what you guys have said plus what I found searching some of the electricians forums on the internet. You basically can't use the "B Phase" or high leg by itself with a single pole breaker.

I do have one last question. Can I use the "B Phase" with any other phase in order to create 240V single phase? So, for instance, if I had a 240V single phase load could I install a breaker between A-B or B-C in order to power it? Or is the B phase ONLY used for 3 phase power and I have to power all of my single phase loads off of A and C?
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Old 06-04-2013, 08:08 AM   #18
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Using 208v "B" phase in open delta?


Quote:
Originally Posted by Biggen View Post
My electrician basically confirmed what you guys have said plus what I found searching some of the electricians forums on the internet. You basically can't use the "B Phase" or high leg by itself with a single pole breaker.

I do have one last question. Can I use the "B Phase" with any other phase in order to create 240V single phase? So, for instance, if I had a 240V single phase load could I install a breaker between A-B or B-C in order to power it? Or is the B phase ONLY used for 3 phase power and I have to power all of my single phase loads off of A and C?
Yes, you can use the B phase with either A or C and have 240 volts.
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Old 06-04-2013, 01:22 PM   #19
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Using 208v "B" phase in open delta?


Since you have an open delta transformer bank, you should probably only use the B phase with the A phase, not with the C phase (assuming the second transformer is across A and B). Otherwise you may find that the voltage is unstable.

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