generator output breaker

[JES2727]

The Kohler 20kw residential generator I installed today has a nameplate rating of 75 amps, but the output breaker is 125 amps. The literature doesn't indicate what size breaker is onboard. This ruined my whole day.
Why does the breaker exceed the nameplate rating by so much? And am I required to size my conductors based on the nameplate, or the breaker?

 

[ceb58]

The Kohler 20kw residential generator I installed today has a nameplate rating of 75 amps, but the output breaker is 125 amps. The literature doesn't indicate what size breaker is onboard. This ruined my whole day.
Why does the breaker exceed the nameplate rating by so much? And am I required to size my conductors based on the nameplate, or the breaker?

Thats strange. The 20wk's I have installed have a 100amp breaker. The 25kw's have a 125amp.

The literature doesn't indicate what size breaker is onboard.

Can you clear this statment up

 

[JES2727]

Can you clear this statment up

The literature I had on hand prior to delivery - the spec's and such -made no mention of the breaker size. Only the output rating of 75 amps. The 125 amp breaker really messed up my day. All the pipe & wire I loaded on the truck was wrong.

 

[hurk27]

The literature I had on hand prior to delivery - the spec's and such -made no mention of the breaker size. Only the output rating of 75 amps. The 125 amp breaker really messed up my day. All the pipe & wire I loaded on the truck was wrong.

None of this makes any sense?

A 20kw generator will supply 83.3 amps@240 volts single phase, unless this is one very non efficient generator?

75 amp @ 240 volts is only 18kw false advertising?

I agree every 20kw generator either had a 90 or 100 amp breaker in it.

Not saying its not possable but somthing sounds fishy

I'd be calling Kohler.

 

[ceb58]

Need to ask what type fuel? LP or Nat. gas
From Kohler, if you have a model 20RES then the rating for nat. gas is 18kw at 75 amp but if it is LP then it is rated at 20kw with an amp rating of 83amp. From their spec. sheet for that model it states a line circuit breaker of 125amp. So size the wire to the breaker and off you go.

 

[Rick Christopherson]

The rating on the generator is based on the mechanical limitations of the engine. The engine is capable of delivering 20kW (26 horsepower). However, the lower the powerfactor of the load, the higher the amperage can be before the power consumption stalls the engine.

If the generator had a KVA rating, this would indicate the maximum amperage the windings in the generator itself could sustain regardless of powerfactor. This is where the breaker size should come from. (30kVA seems a little high though). Most engine/generator pairs are sized based on an 80% powerfactor, so I would have expected the generator to have a 25 kVA rating.

I am not an expert on code, especially in this area, so this is a question not a statement. If your transfer switch or load center has a main breaker at 75 amps, would you not be permitted to size your conductors based on this OCPD?

 

[ceb58]

Need to ask what type fuel? LP or Nat. gas
From Kohler, if you have a model 20RES then the rating for nat. gas is 18kw at 75 amp but if it is LP then it is rated at 20kw with an amp rating of 83amp. From their spec. sheet for that model it states a line circuit breaker of 125amp. So size the wire to the breaker and off you go.

After thinking about it Kohler could have taken the max. 83 amp and added in 125% for surge which would be 103 amp. Then gone up to the next size standard breaker which would be a 125amp

If your transfer switch or load center has a main breaker at 75 amps, would you not be permitted to size your conductors based on this OCPD?

The out put breaker is 125amp so the wire would be sized to this.