generator faulting

[shepelec]

Some genny manufacturers offer a neutral isolation kit. This would allow you to remove the neutral/ ground jumper on the generator and still keep the UL listing intact.

 

[hillbilly1]

Was this generator frame bonded to neutral within the generator? If not I don't see where the fault current will flow to trip the GFCI. The monitoring CT of that GFCI device will see no imbalance unless something returns outside the monitoring CT. If there is no frame to neutral bond that is impossible unless something is damaged in the generator and a path is developed, which as far as I can see that is all the GFCI is going to protect you from. Otherwise it should never trip unless there is a problem between the GFCI and the generator windings. The frame can possibly be same potential of any conductor of the system if there is a fault, but no fault current flows until there is a second fault somewhere, that is just the nature of an ungrounded system.

Yes, it is. It actually had a ground fault module and CT, with a shunt trip breaker.

 

[kwired]

Some genny manufacturers offer a neutral isolation kit. This would allow you to remove the neutral/ ground jumper on the generator and still keep the UL listing intact.

What does the kit consist of? Maybe the necessary tools needed to remove the bonding jumper?

 

[hillbilly1]

What does the kit consist of? Maybe the necessary tools needed to remove the bonding jumper?

I have not seen one for the small portable generators, but for the larger permanent ones they have a buss bar on insulators that replaces the buss bar that is directly bolted to the generator, maybe the portable kits have the same thing?

 

[shepelec]

What does the kit consist of? Maybe the necessary tools needed to remove the bonding jumper?

Directions on how to remove the jumper and a new label to state it now has a floating neutral and should not be used on a jobsite.

 

[Robatt]

I agree, to keep the UL listing intact, change the transfer switch to one that also switches the neutral.

During a recent power outage a client contacted us claiming his 8kw generator w/ gfci protection was going into fault while he attempted to connect it to his 30 amp inlet to power his transfer switch.I suggested that we isolate the grounding conductor from the neutral which were under one terminal and drive a ground rod and connect a #6 cu. wire to it. Any comments. Thanks

That is right way. In the event of a fault we expect the fault current to go back to source which at the moment is the 8KW generator. It has to have an N- G jumper which has to have a ground rod for system stability. It should be separately derived.

 

[kwired]

That is right way. In the event of a fault we expect the fault current to go back to source which at the moment is the 8KW generator. It has to have an N- G jumper which has to have a ground rod for system stability. It should be separately derived.

With an ungrounded generator, if you have a fault to ground all you have done is ground the conductor that is faulted and now you have a grounded conductor. If a second conductor of the system should become grounded you will then have a a condition where a high level of current will flow and will result in opening of overcurrent protection - it is quite safe and has been done that way for a long time.

When you connect such generator to a premises wiring system, the premises wiring system has a connection to ground already so by running an equipment grounding conductor back to the generator frame you are simply making sure that the generator frame is at same potential as the premises wiring grounding system. Should a fault occur in the generator you will not have potential between the generator frame and the premises wiring grounding system.

Why they have started to put GFCI's on these generators I haven't a clue. I suppose putting them on 120 volt receptacles doesn't hurt much, they still should never trip though unless there is a fault within the generator itself, or someone presses the test button. Outside of that the GFCI will never see unbalanced current to cause it to trip, it may still trip from inductive kick-back and other things that it was not intended to trip for but sometimes causes undesired tripping.