3-phase, 3-wire Delta Service W/ Grounded Conductor

Mark Twenhafel

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

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

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.

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Bubbles

nice article. working on one of these now