isolated grounding and the XO of a transformer

[dkstein]

i have a question about isolated ground receptacles and the attachment at the XO of a transformer. I understand about the isolated ground receptacles and all that, but i do not understand exactly how to tie all this together in the panel and the transformer. from looking at the '02 NEC handbook i see the connections for in the panel, but my inspector says that I need to carry conductors from my isolated ground bar to the XO of the transformer. this i do not understand (as it is out of the realm of electrical work that i do), nor do i know how to make this connection. i have a 480/277 system in this building.

this is one of those projects that we as electricians/contractors end up doing for some of our larger clientele, that are other wise things we would never do. my company more specializes in multi-family construction, not commercial work, so i just need a little input on the proper installation.

 

[dereckbc]

Re: isolated grounding and the XO of a transformer

From whatever point you bond the grounded circuit conductor, be it at the Xo or first disconnect, you run two ground wires from that point. The EGC feeder should be green, and IG feeder should be green with yellow stripe. You keep the IG bar in any down stream panel isolated.

 

[Ed MacLaren]

Re: isolated grounding and the XO of a transformer

This sketch may help. It shows a typical system where the bonding is done at the transformer, instead of in the panel.

Ed

[ July 07, 2004, 11:48 PM: Message edited by: Ed MacLaren ]

 

[iwire]

Re: isolated grounding and the XO of a transformer

As has been said XO is the desirable place to go with the IG.

However the inspector can only suggest this though.

The NEC allows you to pass an IG through panels 250.146(D) but it does not require that you do so.