25 foot tap rule

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SK092170

Member
Location
Minnesota
Occupation
Electrician
Hello,

I am having trouble wrapping my head around the tap rules in this situation.

We have a 200 KW diesel generator that has a dual loop cooling system. The remote radiator pump is fed off of the emergency lugs of a 400 amp ATS, so when the generator runs, in theory, the pump runs, However if the emergency breaker to this ATS is opened this pump will not run.
The pump motor is protected by a 30 amp safety switch with 6 amp fuses. The pump motor is a 460 volt, 3 phase, 2 HP motor with a nameplate rating of 3.3 amps and a SF of 1.15.

I would like to move this feed and tap it off to one of the other ATS emergency breakers. There is a 100 amp breaker for one of the other ATS's. If I tap off of the load side of that breaker and feed the radiator pump from there and I install a safety switch what amp disconnect and wire would I need to protect those. The pump is 21 feet from the breaker.

I am thinking a 30 amp disconnect would put it under the one third rule so I have to go with a 60 amp disconnect and 35 amp wire, but I am not sure if I am correct.

Any help on this situation would be greatly appreciated.
 
Power for remote pumps, fans, etc. must be supplied by a tap ahead of all load breakers. See NFPA 110 5.6.7.4
This so that even if all load breakers are off or tripped the EPS will still operate.
 
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