ECN Forum Forums General Topics of the Trade General Discussion Area Transfer switch feeder

I think I'm missing something..must be because I'm tired tonight... If I have a 8000 wt. generator and using 120 volts circuits it can handle 66.6 amps, and on 240 volts it can handle 33.3 amps, should not the feeder and main breaker be rated at 66.6 amps..at the maximum capacity?? I think I might be missing something here.. awfully tired I feel like this is probably a dumb question, but just can't get my head to work right, right now Is the sizing different on generators?? Thanks....Steve

Steve,
Sit down with a coffee, do your calc's again,
I am sure that you have missed something.
Have you figured Power Factor(Cos Phi), in to your calcs?.
How about losses?.

Think double pole. 33.3 x 2 =66.6

Assuming that the generator's 120V output is split across each half of the 240V winding, then loading 4000 watts on each leg (ignoring power factor concerns) would result in 33.3A on each side of the breaker. The neutral in this case would carry no current, just as if the supply were from a xfmr.