Ground Fault Unit

[Dumbo2929]

I have a customer who is adding a breaker to an existing lineup to be used a generator wrap around to the ups loads. As the ups is a 4w output can we get away with simply adding ground fault to the trip unit or do we need to utilize a separate device?

 

[alehman]

It is possible to create parallel neutral paths. If your bypass circuit has a neutral which is in parallel with another neutral (such as the UPS static bypass circuit), the neutral current will divide. A ground fault sensor at the wrap-around breaker would not see all of the neutral current in this case and may experience nuisance trip.