generator main breaker

[clyde snyder]

we wired a 60 KW 3 phase Generac generator with 3/0 copper from the generator to the transfer switch ( rated 200 amps), from the meterpan to the transfer switch and from the transfer switch to a 200 amp main breaker 40 circuit panel. The generator came from the factory with a 250 amp 3 pole breaker. The maximum output of the generator is 208 amps. We failed inspection because of the 250 amp circuit breaker. The inspector says we either have to change the conductors between the generator and the transfer switch or change the 250 amp generator circuit breaker. According to the supplied Generac doesn't have a 3 phase 200 amp replacement breaker. I dont understand the logic since the generator's maximum output is 208 amps.

 

[Cavie]

Welcome to the world of Generac. They also use the term " Utility Service Disconect" Just what is that. It is not "Service Rated Disconect" as it should say. We are looking into this also. the inspector is correct. The feeders must be sized to the breaker. I don't understand why Generac has no 200 amp 3 phase breaker.

 

[suemarkp]

Could the feeder tap rules be used here (is the wire in a raceway, outside or limited in length)?? You have a 200A breaker at the end of the feeder in that "main" panel.

 

[RUWired]

I don't understand why Generac has no 200 amp 3 phase breaker.

I would think that if you had a generator with a maximum ampere rating of 208, you would want a 250 amp (<125%)breaker to run continuiously at that rate.
Rick

 

[dbuckley]

The maximum output of the generator is 208 amps.

No its not. Thats it's rated output, but, it'll deliver more than that into an overload, though probably not for long. The genset OCPD is 250A and the inspector wants the cable protected by the OCPD, thats the logic. If the genset were a POCO transformer would we be having this discussion...?

 

[templdl]

dbuckley,
You are correct, we certainly wouldn't be having this discussion.
If one takes a look at the trip curve of the subject breaker and them compares it to the maximum current that the generator is able to produce I believe one would conclude that the generator is not capable of producing enough current to trip the breaker.
Dave T