10kW electric unit heater

[g-and-h_electric]

Here goes......

Proposing the installation of a 10 kW electric unit heater in a residential attached garage. Calculated load for the heater is 41.667 Amp. Wiring to be #6 THHN /THWN in 3/4 emt.

Based upon article 424.... 60 Amp breaker? Right... Heater could run for more than 3 hours, and chances of finding a "residential plug in breaker rated for 100% duty are slim.

Stop me when I'm wrong


Howard

 

[infinity]

If the heater has a thermostat it might never run continuously at full output for 3 or more than 3 hours. Since your conductors are rated for 65 amps a 60 amp OCPD is code compliant.

 

[retirede]

424.4(B) states that the conductors must be sized at 125%.

Why would you need a 100% rated 60A breaker for a 42A load? 424.22(B) implies a 60A breaker is fine for loads less than 48A.