Generator Main Breakers

[laketime]

Looked at a customer supplied generator yesterday to price for wiring. The customer purchased a 400amp single phase ATS which will be tied into the feed to the residence. The generator has (2) main circuit breakers; (1) 200 amp and (1) 100 amp. The feeders off these breakers will land in the same spot in the ATS like a parrallel feed but from two different circuit breakers. Will this work? Seems to me something is amiss.

 

[charlie b]

Work? Maybe, but I think not.
Code compliant? No.
Safe? Doubtful.

 

[laketime]

Work? Maybe, but I think not.
Code compliant? No.
Safe? Doubtful.

Yeah seems to me this generator was supplying two different loads or something. The customer wants me to change to a larger circuit breaker but I do not want to tamper with how the thing is built.

 

[hillbilly1]

It was built to supply two different transferswitches. Common in commercial, one for emergency egress lighting, other for optional loads.

 

[LarryFine]

The only Kosher way I see to do this is a 200a ATS and a 100a ATS feeding a 200a panel and a 100a panel, respectively.

 

[Birken Vogt]

Usually the generator manufacturer has/had option codes to build it with one big main breaker.

What is the rating of the generator, currently?

 

[JoeStillman]

The manufacturer could swap out the breakers for you, but 400A may be north of what you can get. Depends on the generator size. If it's 75 kW or more, you could probably do it.

But - you don't have to feed a 400A ATS at 400A. You have to do the math and see what the load really is.