Ground rod for portable Generator

[PAULY B]

Does the NEC require a ground rod for a portable generator, i have read articles that say it is required and the bonding between the neutral of the generator and the frame must be removed if the generator is used to supply a transfer switch to a dwelling.

 

[Smart $]

250.30 general statement is followed by...

Informational Note No. 1: An alternate ac power source,
such as an on-site generator, is not a separately derived
system if the grounded conductor is solidly interconnected
to a service-supplied system grounded conductor. An example
of such a situation is where alternate source transfer
equipment does not include a switching action in the grounded
conductor and allows it to remain solidly connected to the
service-supplied grounded conductor when the alternate
source is operational and supplying the load served.

Then we have 250.34...

(A) Portable Generators. The frame of a portable generator
shall not be required to be connected to a grounding
electrode as defined in 250.52 for a system supplied by the
generator under the following conditions:
(1) The generator supplies only equipment mounted on the
generator, cord-and-plug-connected equipment through
receptacles mounted on the generator, or both, and
(2) The normally non?current-carrying metal parts of equipment
and the equipment grounding conductor terminals of
the receptacles are connected to the generator frame.

So if you have a generator which IS a separately derived system, and does not comply with 250.34(A), then yes, the generator is required to have a grounding electrode system.

How often is that with portable generators?

 

[ceb58]

250.30 general statement is followed by...


Then we have 250.34...


So if you have a generator which IS a separately derived system, and does not comply with 250.34(A), then yes, the generator is required to have a grounding electrode system.

How often is that with portable generators?

UL states if its 15Kw or less and it is connected to premise wiring it must be connected as a SDS and switch the neutral. Which would require the N-G bond in the generator.

When a portable generator is used to supply a building wiring system:
1. The generator is considered a separately derived system in accordance
with ANSI/NFPA 70, ??National Electrical Code?? (NEC).

2. The generator is intended to be connected through permanently
installed Listed transfer equipment that switches all conductors other
than the equipment grounding conductor.

3. The frame of a Listed generator is connected to the equipment grounding
conductor and the grounded (neutral) conductor of the
generator. When properly connected to a premises or structure, the
portable generator will be connected to the premises or structure
grounding electrode for its ground reference.

 

[Smart $]

UL states if its 15Kw or less and it is connected to premise wiring it must be connected as a SDS and switch the neutral. Which would require the N-G bond in the generator.

I am aware of that. No debate there (at least I don't want to debate UL vs. actual practice :happyno...

But the OP questioned is a ground rod required for a portable generator? The answer is typically no, even when complying with UL listing (see number 3 in your quote).

 

[GoldDigger]

But the OP questioned is a ground rod required for a portable generator? The answer is typically no, even when complying with UL listing (see number 3 in your quote).

One more factor to consider is the manufacturer's instructions and labeling. Some portable generators provide a conspicuous warning that the generator ground terminal has to be grounded. Others state that it must be connected to a ground rod and hedge that around with conditions that seem to require a local ground rod rather than or in addition to a GEC to the building ground. YMMV.

 

[ceb58]

I am aware of that. No debate there (at least I don't want to debate UL vs. actual practice :happyno...

But the OP questioned is a ground rod required for a portable generator? The answer is typically no, even when complying with UL listing (see number 3 in your quote).

And there lies another dilemma. #1 states it is a separately derived system. So by that and 250.30(A)(3) a rod would be required. All this is dependent if a transfer switch were used. If cords were used to connect electrical equipment, Ie: refrigerator , TV, lamps, from the receptacles on the generator then, no, a rod would not be needed.

 

[Smart $]

And there lies another dilemma. #1 states it is a separately derived system. So by that and 250.30(A)(3) a rod would be required. All this is dependent if a transfer switch were used. If cords were used to connect electrical equipment, Ie: refrigerator , TV, lamps, from the receptacles on the generator then, no, a rod would not be needed.

Well 250.30(A)(3) would not apply to the generators you are referring to, 15kW and under... because the grounded neutral conductor is bonded to the frame and grounding conductor at the gennie. A neutral-switching transfer switch would be required to make the gennie an SDS.

That said, in the real world the typical 15kW and less portable generator installation does not switch the neutral. The NEC does not require the neutral to be switched... only UL does. Yeah, yeah, I know 110.3(B) ? but most people, including most electricians IMO, do not read UL listing requirements... and I'd be willing to bet most instructions included with these gensets mention nothing specifically about switching the neutral. Most will state something to the effect "must be installed to local and national code".