Ground Fault on Feeders

[mshields]

Much of my career has been in the healthcare arena where ground fault on 1000A and higher plus a second level (480V systems) is not negotiable unless on LS and Critical branches. But I recently had occasion to review 215.10 for a non-hospital. And tell me, does Exception 2 mean that if you have say a 3000A service circuit breaker for a building which requires Ground fault protection per 230.95, that you don’t need it on a feeder breaker on the main board rated for 1000A or more (assuming all of the above is on a 480V system). If so, how often would GF be mandated on feeders. I mean, wouldn’t this be a fairly typical scenario. And if so, doesn’t the exception in this case, become, more often than not, the rule?

 

[texie]

Yes, you could just do the main and that is very often the case due to people trying to save $$. In my view it is a very poor practice as I have seen a lot of pretty large buildings put in the dark because a fairly small branch breaker trip on a short.

 

[Russs57]

I agree with Texie.

FWIW being in a healthcare setting I'd like to see the ground fault moved to the smallest breaker, not the largest. I have had 2,000 amp 480V breakers trip because of faults on 20 amp 208V circuits. Sometimes it takes significant time to find these faults and I don't need major sections without power.

 

[texie]

I agree with Texie.

FWIW being in a healthcare setting I'd like to see the ground fault moved to the smallest breaker, not the largest. I have had 2,000 amp 480V breakers trip because of faults on 20 amp 208V circuits. Sometimes it takes significant time to find these faults and I don't need major sections without power.

If you have normal 480 delta to 208 Y stepdown transformers a ground fault on the Y secondary will not be seen on on the 480 side.

 

[Sajid khan]

I agree with Texie.

FWIW being in a healthcare setting I'd like to see the ground fault moved to the smallest breaker, not the largest. I have had 2,000 amp 480V breakers trip because of faults on 20 amp 208V circuits. Sometimes it takes significant time to find these faults and I don't need major sections without power.

Agreed, we in a hospital building had put GF on the multiple outgoing Breakers rather than on the 3200A main Breaker because of the similar reason to avoid the whole building or major part of it in dark.


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[augie47]

Wasn't this put in the Code as Art 230 doesn't cover a SDS ?

 

[Russs57]

My bad Texie. Wasn't thinking before posting. Clearly it was a 277 volt lighting circuit.