generator grounding

[iwire]

Re: generator grounding

Mark that is an interesting question I had not considered.

250.32 Two or More Buildings or Structures Supplied from a Common Service.
(A) Grounding Electrode. Where two or more buildings or structures are supplied from a common ac service by a feeder(s) or branch circuit(s), the grounding electrode(s) required in Part III of this article at each building or structure shall be connected in the manner specified in 250.32(B) or (C). Where there are no existing grounding electrodes, the grounding electrode(s) required in Part III of this article shall be installed.

I think the answer is it depends.

First off the generator is not a 'service'

Supplied from a Common Service

That being the case a generator out on it's own with only the feeder from the generator running into another structure would not require a grounding electrode.

However, many times there will be one or two branch circuits or a feeder running from an AC service in a separate structure to the generators location for the purposes of charging the battery and keeping the engine and sometimes the battery warm.

In that case IMO 250.32 requires a grounding electrode at this separate structure (the generator).

JMO, Bob

 

[don_resqcapt19]

Re: generator grounding

Bob,
As you correctly pointed out, 250.32 does not apply, but given the code definition of structure, does not 250.50 require a grounding electrode at the generator?
Don

 

[iwire]

Re: generator grounding

Originally posted by don_resqcapt19:
does not 250.50 require a grounding electrode at the generator?
Don

Don I am really unsure of that.

Is the generator (the separate structure) served by anything if it does not have branch circuits or feeder from another source?

250.50 Grounding Electrode System.
If available on the premises at each building or structure served,.....

In other words does a generator 'serve' itself?

Not sure we can pin down an answer.

Bob

 

[LarryFine]

Re: generator grounding

Originally posted by iwire:
However, many times there will be one or two branch circuits or a feeder running from an AC service in a separate structure to the generators location for the purposes of charging the battery and keeping the engine and sometimes the battery warm.

In that case IMO 250.32 requires a grounding electrode at this separate structure (the generator).

JMO, Bob

I would think that, for one circuit, the single-branch-circuit exception would apply here, and a rod still not be required.

That being said, I can't think of a reason that a rod would be prohibited. It never hurts to assure equipotential around equipment.

[ January 03, 2006, 08:53 AM: Message edited by: LarryFine ]

 

[George Stolz]

Re: generator grounding

Originally posted by LarryFine:
That being said, I can't think of a reason that a rod would be prohibited. It never hurts to assure equipotential around equipment.

How would a rod assure equipotential bonding? It's notoriously ineffective at that goal, even within 1'.

 

[busman]

Re: generator grounding

Bob,

Why would a generator not be a service?

"Service - The conductors and equipment for delivering energy from the electricity supply system to the wiring system of the premises served."

For a home supplied only by a generator, I still would say that it has a service. For that matter, my home is fed by a generator, it just has a lot of utility company wiring between the generator and my home. Just a thought.

Mark

 

[iwire]

Re: generator grounding

Originally posted by busman:
Bob,

Why would a generator not be a service?

"Service - The conductors and equipment for delivering energy from the electricity supply system to the wiring system of the premises served."

Mark I have to guess you have a 1996 or earlier NEC?

The current definition of service

Service. The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served.

IMO the NEC never intended Article 230 to be used for structures supplied by a privately owned generator.

Its my view that the supply from a privately owned generator is always a feeder.