Service Entrance For Manually Connected DG?

[mwacosta]

I have come across a situation where a DG may be connected on the load side of a feeder breaker in the original service entrance equipment. This DG would only be connected through a manual transfer switch during a power outage and it would be the only power to the building (on one feeder only) until manually restored when utility power returns. In order for the DG protection (breaker) to function appropriately for a ground fault, I would believe you should have to install this as a service entrance equipment for the needed return current. I want to make sure this is OK. I believe electrically it is correct, however the code leads you believe that another service entrance should not be used on this back up supply to this feeder.

Please provide any guidance if you can.

Thanks,

Michael Acosta

 

[ron]

Re: Service Entrance For Manually Connected DG?

If the manual transfer switch does not switch the neutral, then the generator would not be considered a separately derived source and you would need to ensure that the neutral and ground are not bonded at the generator. Service entrance would remain bonded between neutral and ground.

 

[mwacosta]

Re: Service Entrance For Manually Connected DG?

We are to switch the neutral to ensure that the protection will function appropriately, that is why I believe this should be considered a separate service in this case.

MWA