Re: Grounding ? for PTO generator

Posted by John T on August 14, 2005 at 08:55:43 from (130.94.121.246):

In Reply to: Grounding ? for PTO generator posted by jCarroll on August 13, 2005 at 20:19:09:

I would start with the National Electrical Code Article 250 Grounding, then Section 250-6, Portable and Vehicle Mounted Generators.

(a) Portable Generators. Under the following conditions, the frame of the portable generator shall not be required to be grounded and shall be permitted to serve as the grounding electrode for a system supplied by the generator: That means you don’t have to tie it to mother earth, the frame serves as a grounding electrode. (my own comments)

(1) The generator supplies only equipment mounted on the generator and/or cord and plug connected equipment through receptacles mounted on the generator, and
(2) The noncurrent carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.

It looks like if you’re simply running cord connected loads off that portable generator, it needs no grounding (I’m talking about to a grounding electrode here). It does if the generator serves as a Separately Derived System and its Neutral were not tied to any building Neutral. In that case, its treated same as if from REMC’s transformer and needs to be grounded to a grounding electrode.

Nowwwwwwwww, the generator and its Neutral, unless you provide it, has no reference to mother earth. It dont know what earth is and cares less. Any of its voltages are across and relative ONLY to its windings, NOT mother earth. Therefore, “theoretically”, if you stood barefoot on the wet ground and touched one of the hot bare generator terminals you should not receive a shock cuz theres no potential voltage difference between that terminal and mother earth. NOTE I DONT RECOMMEND THAT AND DO NOT TRY THAT AT HOME, there may be a connection to earth if its Neutral is connected to a buildings neutral DONT TRY THAT UNDER ANY CIRCUMSTANCES

Its if n when you tie into a building and then whether or not your generators neutral is tied to the buildings neutral (how many pole transfer switch you use) that determines whether or not it constitutes a Separately Derived System (requires a grounding electrode connection) or not. So long as its Neutral ties to the buildings Neutral there’s already an established grounding electrode, but if not (transfer switch) then you need to supply one to your system.

Clear as mud?? John T, Electrical Engineer retired

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