Re: elect furnace
The heater is 10KW at 208 volts, 14 KW at 240V.
It draws 54 amps at 208v, 62 at 240V.
67.5 and 77.2 are your minimum circuit ampacity - use to find the minimum size wire and branch breaker. So at 208, the minimum breaker would be 70A, and at 240, the minimum breaker would be 80A.
Finally, the maximum breaker sizes are give, and they are the same as the minimum sizes above. So you have to use a 70A for 208V, or an 80A for 240V.
The 60 degree ampacity of #4 wire doesn't seem to be sufficent for a 240V installation.
Steve
[ December 28, 2005, 05:32 PM: Message edited by: steve66 ]