Portable generator bonding.

[hornetd]

Portable generators are being sold with neither conductor of there single phase 120 volt winding bonded to the frame. I would like to here from the people here whether you would consider there use a violation of the US NEC, in an area that has adopted it.
--
Tom

 

[websparky]

Re: Portable generator bonding.

Interesting........ Is the generator listed?

Have you tried a continuity test between the generator and the ground socket of the receptacles and / or the frame?

What brand are they being sold under?

 

[bennie]

Re: Portable generator bonding.

Is there any of the reasons for grounding a system, present in the use of the generator?

You have two potentially lethal conductors, one more increases the hazard by 33 and 1/3 per cent.

 

[hornetd]

Re: Portable generator bonding.

Originally posted by websparky:
Interesting........ Is the generator listed?

Have you tried a continuity test between the generator and the ground socket of the receptacles and / or the frame?

What brand are they being sold under?

I got the information from this thread on the electrical board of doityourself.com
and then questioned a coleman dealer who said that some of the smaller sets are indeed unbonded.
--
Tom

[ September 02, 2003, 09:49 PM: Message edited by: hornetd ]

 

[hornetd]

Re: Portable generator bonding.

Originally posted by bennie:
Is there any of the reasons for grounding a system, present in the use of the generator?

You have two potentially lethal conductors, one more increases the hazard by 33 and 1/3 per cent.

Bennie
That wasn't what I was asking but you know that. I want to know if the code requires that one end of the winding be bonded to the frame on a 120 volt portable engine alternator (generator) set?
--
Tom

 

[iwire]

Re: Portable generator bonding.

Originally posted by bennie:
You have two potentially lethal conductors, one more increases the hazard by 33 and 1/3 per cent.

Bennie you really do make me think, that is an interesting way to look at it.

Bob

 

[bennie]

Re: Portable generator bonding.

A 120 volt portable generator does not require any earth or equipment grounding. You are much safer with an isolated 120 volt power supply.

The portable generator does not supply a premises wiring system.

 

[iwire]

Re: Portable generator bonding.

I have a Coleman 5000 or 6000 watt generator and it has a sticker on it that says "Floating Neutral"

Bob

 

[don_resqcapt19]

Re: Portable generator bonding.

250.34(C) requires that a conductor be grounded.
Don

 

[bennie]

Re: Portable generator bonding.

A portable generator is not a source for the premises wiring system. A premises wiring system is all inclusive of the items listed in the definition. A portable generator can not be considered to power a premises wiring system. The capacity will not meet the minimum size of a premises service.

 

[david]

Re: Portable generator bonding.

II. Circuit and System Grounding
250.20 Alternating-Current Circuits and Systems to Be Grounded.
Alternating-current circuits and systems shall be grounded as provided for in 250.20(A), (B), (C), or (D). Other circuits and systems shall be permitted to be grounded. If such systems are grounded, they shall comply with the applicable provisions of this article.


Does this not require alternating-current circuits in addition to alternating-current systems to be grounded?

 

[bennie]

Re: Portable generator bonding.

Of coursse a portable generator can be grounded, but I can't see any technical reason. An ungrounded source is more safe than a grounded one in this application.

I would not call a portable generator or the items it supplies, a system.

A portable generator is one that can be carried, by definition of the word portable.

A little homelite generator to operate a drill motor is hardly a source for a premises wiring system.

 

[bennie]

Re: Portable generator bonding.

A generator that can be carried is portable.

A trailer mounted generator is transportable.

A skid mounted unit, on a foundation,is permanent.

My interpretations only, but they work for me.

[ September 03, 2003, 03:10 AM: Message edited by: bennie ]

 

[don_resqcapt19]

Re: Portable generator bonding.

Bennie,
I see nothing in 250.34(C) that says anything about supplying a premises wiring system. It just says that when a generator is a SDS, it must have a grounded conductor. All portable generators are SDS.
Don

 

[steve66]

Re: Portable generator bonding.

I've got to agree with Bennie for a small portable generator with receptacles mounted on it. It does not need to be grounded. However, if such a generator was used to supply building wiring, then I would say it would be the installer's job to ground one wire.

250.20 lists systems to be grounded. 250.20(A) doesn't apply to our generator due to voltage, and 250.20(B) doesn't apply because the generator is not a system that "supplies premises wiring or premises wiring systems".

Don:
250.34 is for systems required to be grounded by 250.26. And 250.26 refers to "ac premises wiring systems", so this would not apply to our generator.

 

[bennie]

Re: Portable generator bonding.

Don: This brings us back to the definition of a separately derived system.

No where in the code does it mention that a generator is a separately derived system. It may supply a separately derived system.

If the separately derived system is ungrounded it must be grounded according to 250.30.

I have letters of inquiry, to the NEC staff for clarification of a separately derived system.

I also want to contact the McPartland Group. Their handbook was correct in 1984, concerning a separately derived system.

 

[don_resqcapt19]

Re: Portable generator bonding.

Bennie, Steve,
You guys are correct, the requiments to have a grounded conductor only apply to premises wiring systems. However, based on the Article 100 definition of "premises wiring system", it appears that everything except the load itself is part of the "premises wiring system". An extension cord plugged into the gererator is a "premises wiring system". Based on this, the generator must have a grounded conducotor.
Bennie,
I'll have to look at my old handbook when I get home, but I know that Joe McPartland stressed the current view of SDS connections at some of his code seminars that I attended.

Don

 

[bennie]

Re: Portable generator bonding.

A supply to a premises wiring system is the service.

A generator feeding part of the system is; a generator feeding part of the system.

There is no reason, electrically to ground a portable generator.

 

[goldstar]

Re: Portable generator bonding.

I think it is important, in some cases, to know whether a generator neutral is bonded to ground or not. I had an application at a gas station (specifically for Y2K) where they wanted to be able to pump gas and have some lights on in the event of a power failure. They provided an 8K portable generator and a w/p twist-lock receptacle along with the generator. I installed a 60 amp sub-panel and a 3-pole transfer switch and relocated the pump and light circuits to the sub-panel.

I don't remember if the transfer switch was Generac or Honda but their tech support told me that the neutral of the generator floats. So, I not only had to splice over the phase conductors from the main panel and into the sub-panel but also the neutrals for each circuit. That way on POCO power the neutral is bonded and on emergency power it is not.

I think the key, as others have pointed out, is whether the neutral is bonded to the case. Does anyone know what would happen if you bonded one side if the generator output to ground ?

 

[bennie]

Re: Portable generator bonding.

Yes, you would receive a shock when touching the active conductor.