Breaker sizing

[jgriffin02]

According to NEC, what size breaker is called for in the following situation:

Heat pump air handler with 1/3 hp blower motor
and electric grid heater sized at 5kw.

-Wire feeding from distribution panel is #4 copper
-240 volt single phase power


Old air handler used to have a much larger grid heat with a 60 amp breaker and a separate 20 amp feed for the blower and control.

This new furnace is factory wired to be fed from a single source. It does not have any breakers or fuses on the unit itself for the motor or heater grid.

Thanks

 

[fc]

Re: Breaker sizing

The heat pump should have a Nameplate rating on it. This will determine the size of the OC protection.

 

[ssilbers]

Re: Breaker sizing

Typically the manufacturer will tell you the size of the OC protection. This information is either on a nameplate or in the instruction manual. They may also call out the type of protection, be it a fuse or a circuit breaker. Just make sure to size your wire so that it is protected by the OC protection of the unit.

 

[charlie]

Re: Breaker sizing

Just make sure to size your wire so that it is protected by the OC protection of the unit.

This is a true statement, I just wanted to make sure you were aware that the OC protection of the unit is the actual overload protection of the unit and not the short circuit and ground fault protection of the circuit.