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Anonymous Poster

Reverse Connected xmfr - Grounding

06/25/2010 11:44 AM

208vY primary / 480 volt 3w secondary delta - load balanced

got rod electrode w/ gnd electrode conductor bonded to xmfr frame lug; secondary is 3w w/gnd - ground conductor is connected to xmfr frame gnd lug.

have primary (208) 4w with neutral connected to XO.

any problems? NEC violations?
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#1

Re: Reverse Connected xmfr - Grounding

06/25/2010 3:03 PM

Lots...

With respect to issues from the perspective of the NEC, I can not comment. If this was in Canada, the following would be true...

The primary XO terminal should not be connected to anything. By grounding the transformer case in this fashion you have the potential for two separate equi-potential bonding systems. Which, under fault conditions can cause a voltage potential to be present from one bonding system to the other.

It should be done as follows...

The primary H1, H2 & H3 terminals are connected to your 3 phase conductors from the upstream source. The bonding conductor from the source should go to the lug on the transformer case. The jumper from the primary XO terminal to the case should be removed. A ground fault indicator should be installed on the 480 volt secondary.

The NEC is very similar to the Canadian code, so I am pretty sure this would be good for you also. As always... check the code in effect where this is being installed.

__________________
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