277/480VAC - 1000AMP Service

[dcsva@aol.com]

We have the following:
1000Amp Main Fused Disconnect (VFD) feeding a 1000Amp Automatic Transfer Switch (ATS).
We want to put a wireway above the MFD and ATS to get the MFD load wires to the ATS Line Terminals.
Both the MFD and the ATS are connected to the wireway with 2 four inch nipples. Nipples are about 6" long.
If we run 4 sets of 250mcm (two sets in each of 2 four inch nipples), do I carry a 2/0 EGC with each set per 250-122(f)(1)?

[ September 01, 2003, 11:35 AM: Message edited by: dcsva@aol.com ]

 

[don_resqcapt19]

Re: 277/480VAC - 1000AMP Service

Yes, it appears that you need a 2/0 in each nipple. I see no exceptions for short raceways. If you would connect the wireway to the disconnect and ATS using wireway box adapters, only a single 2/0 would be required.
How are you providing the ground fault protection for the 1000 amp service that is required by 230.95?
Don

 

[dcsva@aol.com]

Re: 277/480VAC - 1000AMP Service

Don,
Do you have any suggestions for GFI with a Fused Disconnect? OR Do I need to go to a Main Breaker Disconnect with Shunt Trip?

 

[brian john]

Re: 277/480VAC - 1000AMP Service

DC:

There re a wide variety of options open to you, depending on the AIC whether or not a CCCB is an option or a bolted pressure switch.

The CB can have GFP built in or utilize a shunt trip. The advantage of the shunt trip is, you can incorporate other options into the design, phase failure, UV, OV trip ECT..........

 

[dcsva@aol.com]

Re: 277/480VAC - 1000AMP Service

We have installed a system (480,1600amp) where the ATS had GFP built-in. But this was a service rated ATS with a Breaker for the Utility and a Breaker for the Generator power service.

Can the Ground Fault Protection be built in to a standard Automatic Transfer Switch as part of its sensing system to determine if it needs to transfer to generator power due to a ground fault

 

[brian john]

Re: 277/480VAC - 1000AMP Service

DC:

If there is a fault downstream from the ATS it will still be their when you transfer sources. I'm not a design engineer (by any stretch of the imagination), but this doesn't seem like the best design to me.