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.
NEC Tap Rule for a generator feeder
- Thread starter tonykarr
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chris kennedy
Senior Member
- Location
- Miami Fla.
- Occupation
- 60 yr old tool twisting electrician
I can't picture what your trying to do here.:-?
- Location
- Massachusetts
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.
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?
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?
ohmhead
Senior Member
- Location
- ORLANDO FLA
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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