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Situation.

I am feeding a 120/208v 3 phase 4 wire 200 amp splitter on the roof of an apartment building which is feeding a step up transformer 208-277/460 (delta to Wye) which in turn is feeding an elevator controller.

The elevator controller does not require a neutral and no neutral will be created at the xo of the transformer. The elevator tech says he does not need the neutral its just a general transformer that they buy. Generally we feed a small auto transformer with 600v and they tap off to 460v. This specific service is 24.7 KV/12.5 KV to 120/208v.

My question is if this transformer is being used as a delta to delta transformer, and it has a factory built in XO point. Do I still ground the XO to my main system ground or will bonding the XO point to my 120/208v system bond work for this application. I dont have much experience with delta to delta step up applications. If there was a fault in the controller i would assume there is a ground fault indicating device. If there was a phase to say the controller enclosure what would happen. The cable going from the secondary of the transformer into the elevator motor controller has a bond wire.

To say the least I am a little confused.


Thanks in advance. I appreciate the education.
 

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Thanks for the reply, I assume you mean back to my main system ground. What would happen if this XO was ungrounded?
Then you would have an ungrounded system and it probably wouldn't be allowed. Plus you'd have to do other crap like putting in ground fault monitoring equipment and so forth.

Just bond X0.
 
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