The equation for amperage is I = W/E, Amps = Watts/Volts. The amperage for the furnace would be, Amps = 15000/240 = 62.5 amps. So to answer the question, yes a 100 amp breaker with a #4 copper conductor will be sufficient to operate a 15 kW furnace. A 70 amp breaker will work but it is cutting the edge a bit too fine as you don't need the furnace to trip off during the winter months (northern hemisphere) if you are away from your home for an extended period of time.
Chat with our AI personalities
The amperage capacity of the main bus bars and the connection of the main breaker to the bus bars.
No. Power to all the circuit breakers will be cut off except for the Main power breaker. The Main power breaker (which supplies power to all other breakers and will say 100, or whatever your max breaker box power is, on it )will have power going to it all the time, unless power is turned off outside the house.
You can reduce the breaker size because that limits the current that can reach the main panel. There is no safety issue other than the significant danger in an unskilled person changing out a main breaker.
For a 100 Amp breaker panel it would be 2 AWG. For 150 Amps it would require 2/0 (2 ought) aluminum wire.
Breaker boxes do not have fuses associated with them unless the main disconnect is independent from the breaker box. If that is the case both fuses have to be the same in the main disconnect that protects the breaker box.