Generators with neutral bonded to the frame and GFCI protection

[meandenno1]

There are hours of commentary on generators with frame bonded neutrals. When used as a temporary power source through a generator inlet and some type of transfer or interlock device, generators with frame bonded neutrals create a ground loop through the main bonding jumper of the electrical service. If the generator is never used for anything else but this one back up scenario, a floating neutral would eliminate the ground loop. The hazard here is if the generator is used for a freestanding application and a short circuit develops with no good ground return to source. The ground loop probably poses a much smaller hazard barring issues with the service grounding and bonding. With the introduction of generators with full panel GFCI protection (including the 30 or 50 amp twist lock outlets) This ground loop is sufficient to create a circulating current that exceeds the trip threshold on most GFCI protection. There are some GFCI rated transfer panels on the market but these panels don't address an issue with panel mounted interlock brackets or transfer equipment that switches the entire service load to the generator back-up. In these cases, the main bonding jumper remains in the circuit and the GFCI devices reads this as a high impedance fault and trips. Disconnecting the GFCI device in the generator might seem like an option but it will probably void the equipment warranty and could be hazardous if used in a jobsite application or something similar. Most homeowners are not going to foot the cost of turning their portable generator into a separately derived system and isolating the SDS from the premises grounding grid, yada yada...just to stop the GFCI device from tripping. OK electrical problem solvers...what's the answer?

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