Grounding for Portable Generator

[rpickett_01]

Can anyone tell us where in the NEC it states that the code "requires that the frame and external electrically conductive parts of a generator be properlly connected to an approved earth ground." (Quote is taken from an owner's manual for a Generac Portable generator.)

 

[charlie]

Re: Grounding for Portable Generator

250.34 Portable and Vehicle-Mounted Generators. The frame of a 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 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 non?current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.

110.3(B) Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

The bottom line - The Code doesn't say you are required to ground it; however, you are required to follow the instructions included with the listing.

 

[charlie b]

Re: Grounding for Portable Generator

Let me see if I can make the waters even more muddy. This is from Article 100 Definitions: ?Ground. A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth or to some conducting body that serves in place of the earth.?

In the case of a portable generator, the external metal case is permitted (by the article the other Charlie has quoted) to be used as a ?conducting body that serves in place of the earth.? As long as the only loads supplied are plug & cord types, with the receptacles being mounted on the generator itself, then a connection to planet earth is not required by code. Note that if the loads are supplied by some other means (e.g., the portable generator powers a portable distribution panel), then 250.34 no longer applies, and an earth ground is required by code. The manufacturer can still require an earth ground, and the NEC requires us to follow the manufacturer?s requirements, but that is a different issue. In other words (and to directly answer your specific question), the manufacturer is NOT citing code, but rather is imposing its own set of requirements.

 

[iwire]

Re: Grounding for Portable Generator

What if my portable distribution panel is cord and plug connected and my loads are cord and plug connected to that panel.

250.34(1) The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both,

The reason I ask is that it states "equipment"
not "utilization equipment"

Article 100 2002 NEC

Equipment. A general term including material, fittings, devices, appliances, luminaires (fixtures), apparatus, and the like used as a part of, or in connection with, an electrical installation.

Utilization Equipment. Equipment that utilizes electric energy for electronic, electromechanical, chemical, heating, lighting, or similar purposes.

[ June 17, 2003, 07:16 PM: Message edited by: iwire ]

 

[bennie]

Re: Grounding for Portable Generator

What will a ground rod do? There will be no switching transients. Lightning striking the generator will eat the rod.

On construction sites where there is concrete and rebar, the frame of the generator should connect to the rebar.
The reason is...should the rebar become energized by contact with a faulty cord, the circuit will dump.
I received a jolt from the frame of a drill motor,
while standing in water, on a concrete deck.

I got a reverse ground fault.

[ June 17, 2003, 10:33 PM: Message edited by: bennie ]

 

[iwire]

Re: Grounding for Portable Generator

Originally posted by bennie:
What will a ground rod do? There will be no switching transients. Lightning striking the generator will eat the rod.

On construction sites where there is concrete and rebar, the frame of the generator should connect to the rebar.
The reason is...should the rebar become energized by contact with a faulty cord, the circuit will dump.

Bennie, I was thinking the same thing and would add building steel to the list.

Was the circuit you got hit by a GFCI protected circuit or where you just lucky not to get hung up?

 

[bennie]

Re: Grounding for Portable Generator

Bob: Correct, everything conductive that could accidently become energized should be connected to the frame/neutral.

This incident was at the John Day Dam, long time before GFCI's. The generator was for temp-power. There was a lot of very mad workers. Many others got zapped when touching the power tools.

The problem was... the brewery cord used for temp lighting was tied to the rebar. When the wire wore through it energized the rebar.