3-phase, 3-wire delta service w/ grounded conductor - Contractor Talk - Professional Construction and Remodeling Forum

Mark Twenhafel · 11-11-2007, 03:53 PM

Third question:
Reading 250.24 (C)(1): The last sentence refers to "[t]he grounded conductor of a 3-phase, 3-wire delta service...".

Um, that doesn't compute for me. In a 3-phase service, there are 3 hots. And, it doesn't say corner grounded or anything. Here's a picture of what I think a 3-phase, 3-wire delta service looks like:

So, what's the grounded conductor on 3-phase, 3-wire delta service?

Thanks.

goose134 · 11-11-2007, 10:05 PM

I believe it is a reference to corner ground systems. Otherwise known as grounded B phase. I've never come across one, but I've heard of them. Here is a link for more reading:
http://ecatalog.squared.com/techlib/...008926800b38e9

Magnettica · 11-11-2007, 10:28 PM

The NEC 2005 HANDBOOK says that only if the utility company provides a grounded conductor do you need to bond and install a grounding electrode system to the service.