equipment ground for transformer

[tom baker]

Re: equipment ground for transformer

Exlporer: It may be a violation of 110.3(B). I installed a step up transformer once, it was a delta 208 x 480/277, and cost double what a step down would cost. its sold as a step up, so I maintain unless the transformer lists a delta 208 x 480/277 connection it would be a violation.

 

[jim dungar]

Re: equipment ground for transformer

John,

This is a wye-delta transformer design issue. For example, a problem occurs during situations where one primary line conductor is opened.
Here is a link to Hammond Power Transformers:
http://www.hammondpowersolutions.com/temp/faqretrieved138575.089703412.html
and Jefferson Transformers:
www.jeffersonelectric.com/techfreq.html

Tom,
I know of no manufacturer that makes a standard 208V to 480V delta step up transformer. All manufacturers make a 208-480Y/277. All manufacturers provide information on how to reverse connect their transformers.

This is a link to Sola/Heaviduty:
http://www.solaheviduty.com/support/faq.html#Q36

and GE refers to reverse connections in the installation manual, see page 7:
http://www.geindustrial.com/products/manuals/475A667AAP001.pdf

 

[websparky]

Re: equipment ground for transformer

I agree with Jim.

I have installed several XFRs like this AND always connected the XO.

Never had a problem.

 

[curt swartz]

Re: equipment ground for transformer

Dave,

Are you saying that you connected a 480 delta - 208Y transformer in reverse but grounded the X0 terminal? Jim is saying just the opposite and I agree with him, the X0 terminal should not be grounded.