Neutral/Ground bonding in critical loads panel for backup system

[photonboy]

I know that neutral and ground can be bonded in a fused AC disco when a supply side tap is performed, the logic being that the disco essentially becomes a service disconnect as it is bypassing the MSP.

I am looking at an Enphase IQ System Controller critical loads panel and the neutral bar is bonded to the enclosure. My instinct tells me NO but I'm wondering if, in the case of an outage, does the critical loads panel become the MSP?

Also, in the case of normal daily operation with no outage the critical loads panel is just another sub-panel but now we have two places with neutral/ground bonded, could this result in "objectionable current"?

 

[wwhitney]

Also, in the case of normal daily operation with no outage the critical loads panel is just another sub-panel but now we have two places with neutral/ground bonded, could this result in "objectionable current"?

Yes, and that definitely tells you that the critical loads panel must have N and G separate.

Cheers, Wayne

 

[jaggedben]

The Enphase System controller contains an autotransformer that connects to the neutral and maintains the 120V line-to-neutral voltage when off grid. It is not a separately derived system, i.e. the neutral is not disconnected from the service panel when the System Controller goes off grid. Therefore there should still be only a single N-G bond, which is at the service.