Existing 3-pole ATS on Service with GFP

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32Lateralus

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Location
West Coast
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Electrical
Service is 3000A - GFP main
Existing 600A feed off service to Life safety ATS. This is a 3-pole ATS.

Owner is considering adding a Generator for full bldg backup.
After GFP main in service, bussing would be modified to feed (N) ATS and back into the service to feed rest of the board.

My understanding is due to the GFP main, the (N) ATS should be a SDS with N-G bond and a 4-pole ATS.
However, this generator will also be feeding the existing life safety ATS that is 3-pole.

This is no good, right? Would the existing ATS need to be upgraded to 4-pole as well?
 
hillbilly1 said:
Caveat though, will the existing generator remain in operation? You can have redundancy. If so, the old tswitch can remain.
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Old generator would be removed for spatial requirements

New generator will feed entire SES and (E) life safety. So technically new gen will start up and transfer over life safety first, then the full SES ... then life safety will then transfer back to 'normal' side cause it will sense 'normal' power when the gen backs up the full SES. is that acceptable for the ATS to essentially be fed on both sides from that gen?
 
hillbilly1 said:
I believe you will need a second breaker in the generator to feed the old (new) life safety transferswitch.
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Yes it will be off of separate breakers inside the gen. So sounds like I am on the right track. Everything should be good, just replace that existing ATS to 4-pole since gen will be a new SDS.

So the reason that old ATS was 3-pole was due to the immediate upstream normal breaker not being GFP? Since that old ATS is fed from a 600A inside the SES and not the GFP main it did not require 4-pole? Meaning the existing gen would not have N-G bond?
 
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