Onan 4.0 KY (gas) generator not putting out 4 kw

[flybynight]

I have a 2010 Onan 4KW KY gas generator that seems to be running okay except that I can't seem to get a full 4000 watts out of it before tripping the main breaker (near the start switch).

During these cold winter months (Rochester, NY) I have been starting up the generator every 2 weeks and after letting it warm up, I run it under load ( 3 ceramic heaters ) for 1 hour.

I measured each of the heaters using a Kill-O-Watt meter to measure their actual load. But when I set the combination of the 3 heaters for a total of anything over ~3400 watts, the main breaker trips after about 10 seconds. Below 3400 watts the generator will run with no problems.

Not much else is running while I am running this test. The only thing might be the charger for the 12v starter battery, I can't see that taking 400 watts to charge.

Is this behavior normal? - Or is the 4.0KW rating a surge rating (the manual doesn't indicate this). I am at ~1000 ft. elevation. Is the elevation derating causing the drop. I thought this was associated with the engine power itself which doesn't seem to have a problem delivering 4kw of power until about 10 seconds later when the breaker trips.

Thanks,
FBN.

[JRTJH]

Here are the specs from "Generator Joe" (This is an Onan dealer):

This model runs at 3600 RPM and generates 4 kW (4 kVA) 60 Hz, of Standby (emergency or maximum) power and 3.6 kW prime (continuous) power at a primary voltage of 120/240 VAC, single phase, 60 Hertz, with 10% voltage accuracy.

So in reality, you're looking at 4KW max with a 3.6KW continuous power output. If I remember correctly, the circuit breaker is set at 33.3 Amps which would trip at about 36.3Amps @ 110VAC.

Also remember that "winter blend gasoline" doesn't have as much octane rating as "summer blend" so you won't produce as much horsepower as you would in the spring/summer/fall and may well bog down the engine at higher output demands.

[BlindGuyNAR]

Originally Posted by JRTJH

Here are the specs from "Generator Joe" (This is an Onan dealer):

This model runs at 3600 RPM and generates 4 kW (4 kVA) 60 Hz, of Standby (emergency or maximum) power and 3.6 kW prime (continuous) power at a primary voltage of 120/240 VAC, single phase, 60 Hertz, with 10% voltage accuracy.

So in reality, you're looking at 4KW max with a 3.6KW continuous power output. If I remember correctly, the circuit breaker is set at 33.3 Amps which would trip at about 36.3Amps @ 110VAC.

Also remember that "winter blend gasoline" doesn't have as much octane rating as "summer blend" so you won't produce as much horsepower as you would in the spring/summer/fall and may well bog down the engine at higher output demands.

X2 on everything said above and 400 watt estimate on the converter might be low. My 75 amp converter pulls 1300 watts.

[flybynight]

Thank you for the info.

I guess I'll consider that it's meeting spec.

Now I just hope that the RV antifreeze manufacturer that guarantees the -20F spec is accurate, because it sure is getting tested a lot this winter... -11F last night. I guess I'll find out in another 6 weeks or so.

-J