NEC Tap Rule for a generator feeder

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tonykarr

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A 750 KW emergency generator feeds a part of a building load by underground feeder. There is a 1200A circuit breaker at the generator which is about 80 Ft away from the building, and a 1200A disconnect in the main building electrical room. Can a tap be made at the disconnect output, downstream from the generator circuit breaker? Is this considered a feeder as described under NEC 240-21b? The proposed tap circuit is strictly used for redundancy in case the existing ATS fails.
 
Nor can I, but, that withstandimng it sounds like a tap. What size /number of condcutors come to the building and what size are you going to use on your "tap" ?
 
It sounds to me like it is not a 'tap'. It sounds to me like a 1200 amp feeder that he wants to split into two directions, one to an ATS and one to a disconnect.

As far as that part assuming both directions of the feeder are rated for 1200 amps there is no 'tap'.

I am interested in the full lay out of this as there might be other issues.
 
Existing Conditions: The feeders from the generator to the building are (3) 4#600+1#4/0 Gnd. and they terminate into a 1200A disconnect (non-fused) at the building. These feeders are protected by a 1200A circuit breaker at the generator. The disconnect feeds a 1200 ATS. The ATS feeds general building loads, 80 KVA UPS and A/C equipment.

We want to add another ATS (redundant), 600A parallel to the existing 1200A ATS to feed another 80 KVA redundant UPS and other critical A/C equipment for a server room. We would like to tap a 600A circuit ((4) 350+ 1#1Gnd) into the output of the 1200A disconnect and install a 600A circuit breaker next to (less than 25 Ft) the 1200A disconnect using the tap rule. Can we do this?
 
tonykarr said:
Existing Conditions: The feeders from the generator to the building are (3) 4#600+1#4/0 Gnd. and they terminate into a 1200A disconnect (non-fused) at the building. These feeders are protected by a 1200A circuit breaker at the generator. The disconnect feeds a 1200 ATS. The ATS feeds general building loads, 80 KVA UPS and A/C equipment.

We want to add another ATS (redundant), 600A parallel to the existing 1200A ATS to feed another 80 KVA redundant UPS and other critical A/C equipment for a server room. We would like to tap a 600A circuit ((4) 350+ 1#1Gnd) into the output of the 1200A disconnect and install a 600A circuit breaker next to (less than 25 Ft) the 1200A disconnect using the tap rule. Can we do this?
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Well YES why not its fine you have protection with 600 amp breaker just that part is fine .

But whats you real load on that 600 amp because your 750 kw genset is only good for 902 amps?

Whats your loads ? Then we can say YES or NO but its a pretty thin line as your adding to whats watts now and voltage drop thats a long pull from generator meaning the 1200amp run ?
 
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Assuming you mean (2) sets of 350's, what you propose is allowable as far as the general tap rules are concerned.
 
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