Portable Generators Floating/Bonded Neutral

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tom baker

tom baker

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Portable generators intended to use a power cord and plug into an inlet come in 2 flavors, floating and bonded neutral.
The floating neutral would be used with a non SDS transfer switch to prevent objectionable current and keep the GFCI on the generator from tripping (if I understand it correctly)
Question 445.20 A for an floating neutral, 15 and 20 A require GFCI, how is that GFCI wired? Also a provision for the 15A & 20 A to be interlocked with 250V outlet

Question What type of generator are you finding commonly, floating or bonded? Do your customers understand this or do you just wire it up?
 
I believe that if the generator provides GFCI protection for the 15 or 20 amp receptacles then the neutral must be bonded. I've yet to see an off the shelf generator wired differently.
 
I think it was Mike holt live had an extended discussion on the topic, according to the discussion the portable gen sets are getting new requirements in the 2020 cycle. 1 being bonding must be in place for listing purposes so unlikely to find a new portable that is unbonded. Personally this it was a push by the big 3 to keep use of portable gen sets from being used, pushing their larger fixed units, just a theory.
 
infinity said:
I believe that if the generator provides GFCI protection for the 15 or 20 amp receptacles then the neutral must be bonded. I've yet to see an off the shelf generator wired differently.
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A GFCI should function just fine with a floated neutral.

With a floated neutral you have an ungrounded neutral, so a ground fault might not supply enough current to trip the GFCI...but if the fault doesn't trip the GFCI then the fault isn't a serious shock hazard. If the fault current is sufficient to trip the GFCI (because of leakage or capacitive coupling) then the GFCI will trip.

With that said, the small portable generator I just bought came bonded, with instructions for how to remove the bond.

-Jon
 
winnie said:
A GFCI should function just fine with a floated neutral.

With a floated neutral you have an ungrounded neutral, so a ground fault might not supply enough current to trip the GFCI...but if the fault doesn't trip the GFCI then the fault isn't a serious shock hazard. If the fault current is sufficient to trip the GFCI (because of leakage or capacitive coupling) then the GFCI will trip.
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I agree with that.
However, if the generator is not bonded and one of the L or N GFCI outputs has a fault or leakage to the EGC then it will not trip if there's a fault to EGC on the other line or neutral output.That's because all fault currents would be flowing between the GFCI output terminals and none of it would be bypassing around the GFCI current transformer.
 
synchro said:
However, if the generator is not bonded and one of the L or N GFCI outputs has a fault or leakage to the EGC then it will not trip if there's a fault to EGC on the other line or neutral output.That's because all fault currents would be flowing between the GFCI output terminals and none of it would be bypassing around the GFCI current transformer.
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Ahh, yes. The GFCI would not be able to detect this double fault, where both L and N fault to the EGC.

-Jon
 
A lot of the Honda portables come from the factory with floating neutral.

At least one ahj here wants me to list the type of generator the customer has when I apply for the permit, or is planning to purchase, so they can make sure it is/isn’t an SDS.

Ive had customers purchase generators that have bonded neutral, and Ive removed the bonding for them.

I know that on the Honda’s we have here at the ranch with floating neutrals, the GFCI receps work just fine.

I have one with a floating neutral mounted on the truck, and I built a pigtail GFCI for it, and it works fine.
 
I think listing requirements possibly have changed over the years.

I have a 8k portable that is about 15 years old. Has floating neutral, a 14-30 receptacle (no GFCI on that) and 2 - 5-15 GFCI receptacles. GFCI shouldn't ever trip when used as stand alone system. But you sort of have little shock risk in that situation either so it doesn't matter much. When connected to premises wiring system the neutral becomes grounded and then you could easily have a ground fault that allows enough current to flow to trip those GFCI's.
 
I found a generator at Harbor Freight (yes I know :unsure:), its for my granddaughters family, that has a floating neutral and a 20A GFCI. But the information shown does not indicate if a floating or bonded neutral, I had to email and ask. Most generators will be labeled if floating or bonded.
 
tom baker said:
I found a generator at Harbor Freight (yes I know :unsure:), its for my granddaughters family, that has a floating neutral and a 20A GFCI. But the information shown does not indicate if a floating or bonded neutral, I had to email and ask. Most generators will be labeled if floating or bonded.
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If fairly new yes. If from HF or other similar places, maybe.
 
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