Generator Switchboard Taps

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infinity

infinity

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I have a generator switchboard (480Y/277) which is fed directly from the 725 KW generator output and set up as an SDS with a bonded neutral and a GEC run to the GES. The plans call for a set of disconnect switches (60 and 400 amp) to be tapped to the line side of the switchboard. A few questions have come up:

1) Are these considered feeder taps or is it treated like a service?

2) How do you size the EGC run with the tap conductors or do you run a neutral conductor and use that to bond all of the metallic parts on the line side of the fused disconnect switches?

3) Is a GEC required to each disconnect.

If this is setup as a non-SDS (bonding jumper removed) I would assume that regular tap rules would apply.
 
IMO, it would not be a service based on the Code definitions.
It looks to me like 250.30 & 250.32 would be the applicable Articles.
I see a bit of a problem with the design in general looking at 240.21(G), 445.19, and it's reference to 240.15(A)
 
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If the generator has OCP at the source and the SBJ is at the source and the SSBJ is with the feeder conductors to the switchboard, then treat it like any other feeder tap. Size EGC same as phase tap conductors. Keep all EGC and neutral conductors separate. If OCP is not at gen set, then 445.13 is a problem and taps cannot be made ahead of OCPD.
 
The generator feeds a switchboard with no main, just 4 circuit breakers, the line side of that switchboard is also tapped to feed two disconnects, one for the fire pump the other to power the fire alarm system ATS.
 
If the generator does not have an OCPD and its a main lug switch board, then conductors feeding 60 and 400 amp disconnects would need to be same size as main feeder switch board conductors.
 
RUWired said:
If the generator does not have an OCPD and its a main lug switch board, then conductors feeding 60 and 400 amp disconnects would need to be same size as main feeder switch board conductors.
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Based on 445.13? Then wouldn't the bus feeding the four circuit breakers integral to the switchboard also require "full size" bus?
 
infinity said:
Based on 445.13?
Click to expand...
For conductors, yes.
infinity said:
Then wouldn't the bus feeding the four circuit breakers integral to the switchboard also require "full size" bus?
Click to expand...
Best I could say is the rating of the switchboard would be not less than calculated load.(based on 225.39) So can you have conductors rated higher than rating of disconnect , Yes. In your case I think a switch board section rated for the new loads having capability for landing the conductors rated for the generator are in order.
 
if you agree with what I say and need a solution, maybe you can relocate 1 of the existing feeders to a new panel board along with the 60 and 400 amp feeders. Use that space to feed the new panel board.
 
Even with the two taps the total connected load is less than the generator output and I'm assuming the manufacturer generator conductors are of adequate size.

I'm just trying to wrap my head around this because this is a very common local installation practice and I'm assuming that it's actually required to be done this way. Problem is that I can't seem to find any documentation that says so. :slaphead:
 
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