ECN Forum Forums Code Related Discussion NEC & other Code issues Generator neutral bonding

gfretwell,
Whom are you directing this statement to and can you expand on your statement?
Don

I know that what I am about to tell you can be dismissed as anecdotal but I have personal experience with getting a shock from a generator. While operating at a pier fire in San Francisco as a member of that cities Fire Reserves I was assigned to deploy a Circle D flood light down the side of the pier shed. As I was maneuvering around an obstruction at the edge of the pier deck I received a shock that prevented me from letting go of the flood light. I still had control of my other hand so I was able to hold on to the obstruction and avoid falling into the harbor. Once I had stumbled or fallen back to level pier deck I used my free hand to unplug the cord from the Circle D light. I don't want to think about what would have happened to me if I had fallen into the harbor with my left hand locked to the handle of a faulted flood light. The generator set was quite large as it was the departments special light and power unit. The neutral was bonded to the frame. The cord was two wire with no Equipment Grounding Conductor. The generator frame was not deliberately earthed but it may have been bonded to the truck frame. One possibility was that the other equipment deployed from the unit may have been the other side of the circuit but wouldn't that have meant that there were two complimentary faults in two different items. If one of the other loads had an Equipment Grounding Conductor that might explain the return path. Both the fireboat Frank White and the Fire Boat Phoenix were pouring thousands of gallons of salt water onto the pier. We had been operating for over six hours at that time and I was soaked to the skin. The conclusion I drew from that experience was that if the neutral is to be bonded then the equipment should have an EGC. Conversely if the neutral was not to be bonded then it should supply double insulated portable equipment only in order to insure complete isolation under real world conditions.
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Tom H

Don surly you are following this same thread at Mike's?

I am curious to why you would apply the NEC to a UL listed piece of equipment?

Darryl SHOUTING (using all capitols) is not necessary, it does not prove your point and it is generally considered bad forum etiquette.

Bob

If you ground the generator nutral to the frame then you must ground the frame and treat the generator as a separatly derived source and switch the nutral at the transfer switch. However if the nutral is separate from the frame then they are bonded at the main disconnect and are treated as a non-separetly derived system. Then you do not switch the nuteral at the transfer switch. Both are according to the code.

Bob,
Just because a product is listed doesn't mean that is in compliance with the NEC. In my opinion, any connection to the generator, either hard wired or cord and plug connected, is premises wiring and this wiring must originate from a grounded system. If there is no internal bonding jumper, it is not a grounded system and you can't use the power from that system and be in compliance with the NEC.
That being said, I think that in most cases, an unbonded generator is safer than a bonded one.
Don

Using your definition, the generator on my bicycle and the wires to a light on the front of it would be covered by the NEC. My bicycle is not grounded nor does it have listed CL2 cabling. If a generator, battery, or similar is not really portable (i.e. it weighs over 200 lbs and doesn't have wheels or it is hard wired into building wiring) then I could believe your interpretation of premesis wiring.

Mark the discussion was mainly about PORTABLE generators... (with wheels)

The discrepincies are, with a two pole transfer switch everyone seems to concur that you need to remove the neutral bond in the Gen. If that is done is the Gen still safe for stand alone use without the neutral bond that was factory installed and UL approved.

In the USA most if not all transfer switches are sold as only two pole units... (Canada sells 3-Pole, as is really needed)
The hesitation was in changeing factory wiring on a Gen and it's then safety factor... (and the Bonding jumper size was a side point)

That was my point, although I went a little far with the bicycle analogy. Don seems to think that anything plugged into a portable generator, when used in the portable mode without any transfer switch, is required to be grounded because just about everything is premises wiring. Certainly if you connect it to your house wiring via a transfer switch, then it must be grounded and I don't question that.

Either a 2 pole or 3 pole tranfer switch is fine as long as you've used the correct one based on bonding jumpers and grounding. The issue seems to be if you've removed your bonding jumper do you have an unsafe or nocompliant generator when you unplug it from your transfer switch. I would say it is safe. Whether it is compliant is being debated.

[This message has been edited by resqcapt19 (edited 01-22-2005).]

Yup he is right, that bike generator is a premises.

Next time I see someone dragging one of those little generators back to a campsite in the woods I will be sure they drive 2 rods or show me a grounding survey (<25 ohms). ;-)
Better be doing that with their flashlights too.

Seriously, when you ground one of those legs you make the other one 120v above everything else in the environment. If you float both, sitting in the dirt does not give you a return path. The power supply on a lab bench is the same way. They run it through am isolation transformer and do not ground either leg. That way there is not a fault path to the bench.