GFPE

[hhsting]

Please see attached sketch. I have High Rise that has 277/480V main service switchboard 2000A.

The switchboard feeder has Bkr#1 Standby Load and second feeder has Bkr#2 to emergency life and safety load. Downstream has ATSs and emergency generator.


As I read it emergency systems are Not allowed to be on Ground fault protection only detection is allowed NEC 2017 section 709.6(D)

However NEC 2017 section 215.10 requires GFPE on feeder

Its confusing Questions:

1. would GFPE be allowed on in swtichboard BKr#2 that feeds emergency load or Bkr #1 that feeds standby load attached sketch or not?

2. Would GFPE be allowed at the generator breaker?

 

[Rock86]

The GFP on the service entrance is bypassed when you switch over to EM power. What size is Breaker #2?

 

[hhsting]

The GFP on the service entrance is bypassed when you switch over to EM power. What size is Breaker #2?

Bkr#2 is 400A but the switchboard main breaker is 2000A.

 

[Rock86]

In the event of power loss, how does the ATS work, and will Bk#2 still have GFP? Think about it that way. If you lose power, what size is the protection of the EM system, and does 700.6(D) apply?

 

[hhsting]

In the event of power loss, how does the ATS work, and will Bk#2 still have GFP? Think about it that way. If you lose power, what size is the protection of the EM system, and does 700.6(D) apply?

I dont follow what you are saying. Its confusing. The bkr#2 is below 1000A but The 2000A main breaker service switchboard can it have GFPE based on NEC 2017 section 700.6(D)?

 

[d0nut]

In your sketch, the only breaker that requires GFPE is the 2000A main. GFPE would be allowed on any of the other breakers on the normal side, but would not be required.

 

[Rock86]

I dont follow what you are saying. Its confusing. The bkr#2 is below 1000A but The 2000A main breaker service switchboard can it have GFPE based on NEC 2017 section 700.6(D)?

Like Donut was saying... if you think about your system, under normal operation the 2000A at 480/277 would full under 215.10. When power goes down, your ATS will switch to the emergency generator and now your emergency circuits are only protected by the 400A break and is no longer protected by the GFP on the 2000A main.