# Time factor



## micromind (Aug 11, 2007)

If you're thinking of backfeeding a standard 480 to 120/208 3ø transformer, it certainly will work. I've done it a number of times. 

On the 208 side, don't connect the neutral to anything, and remove the XO to ground bond. XO needs to be isolated. 

On the 480 side, you'll have 480 only, not 277/480. If you need 277, you can get 3 single phase transformers and connect them zig-zag to create a neutral. 

If you're using just 480, ground H2. Then you have a conner-grounded delta system. 

The inrush current on the 208 side will be quite a bit more than normal. A basic standard breaker might trip. 

Rob


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## hooch (Sep 18, 2010)

rob, thanks for the reply we are in an bind and that was the only thing to try,the building has to be back up by tomorrow and to get the right transformer would have taken 3 weeks:thumbsup:


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## frenchelectrican (Mar 15, 2007)

Also just keep in your mind when you backfeed or run it in reverse mode expect the 480 volts side it will read little higher voltage than normal unless you have one of the tappers there you can adjust it but not alway the case.

Merci,
Marc


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