Furnace Circuit Breaker Size

Difference between circuit breaker and isolator disconnector circuit breaker size calculation for continuous non contentious load.

Furnace circuit breaker size.

80 of breaker max single phase breaker size wire size based on copper thhn wire increase one size when using aluminum conductors at 115 volts at 230 volts 15 amp 14 1 380 2 760 20 amp 12 1 840 3 680 30 amp 10 seldom used on 115 voltage 5 520 40 amp 8 seldom used on 115 voltage 7 360 50 amp 6 seldom used on 115 voltage 9 200 60. The residential gas furnace needs power only to run the motor so it usually needs a 15a breaker if it doesn t share the circuit with other consumers in the home. However typically electric furnaces require a draw between 60 and 80 amps. The furnace uses the power.

The switch connects to the furnace inside a wiring box. Because of the lower amperage rating of the 30 amp circuit of the new furnace the existing 60 amp circuit that will be connected to the 30 amp circuit should be changed to the 30 amp rating. A 30a circuit breaker can safely carry the exact 30a current but nec suggests 80 as a safe current limit as compared to the rated current. A single sheathed cable runs from the circuit breaker to a single pole light switch located next to the furnace.

The exact amps an electric furnace requires is solely based on the size of the furnace and its performance capabilities. The blower and control circuit for a modern gas furnace uses its own 110 to 125 volt circuit breaker. The best thing you can do is check the nameplate on the furnance where you will find the power and breaker requirements for your specific unit. This will provide the necessary overload protection for the circuit wiring and internal furnace components that are part of that 30 amp circuit.