I'm installing a 208/240 electric garage heater. The KW is 7.5/10.0 and the AMPS is 36.0/42.0, BTUs per hour is 25.6/34.1.

I plan on using a 50AMP breaker for this heater and running number 8 wire from my main panel which is about 100 ft from the heater. Is the wire size and breaker size correct for this heater?

THanks

What is the system voltage supply?

208/240 Volts

Sorry, but the voltage supply in the building is either one or the other. I need the actual voltage so I can do some calculations. Is this at home or a commercial business?

Sorry, this is in a home. It will be 208.

208 volt is a commercial voltage, unless your home is an apartment or condo as part of a large multi-dwelling building.

A normal single family home is usually 240 volts.

If 240 volts and using Romex cable, then the #6 copper wire on a 50 amp breaker must be used.

If 208 volts and using Romex cable, then you can use #8 copper wire and a 40 amp breaker.

I think you need to be sure of the supply voltage you have.

Tkrussell,

You are correct it should be 240 as this is a home. We refer to is as 220 Volts. Everything we run is in conduit as Romex is not allowed. Would this change the wiring size?

Thank you for your help. It's so much easier to do it right the first time vs re-doing it or much worse having the risk of a fire.

Thanks

120/240 volts is the standard voltage in residential application in the US. There is no such think as 220 volts, it went away long ago with the Corvair.


Ok, then with conduit, you can pull #8 copper wire with THHN or XHHW insulation. This will be fine for either a 40 or 50 amp circuit. Your heater will be drawing the 42 amps and consume the 10KW.

The #8 will result in 2.7 % voltage drop, the recommended max is 3%, so you will be fine.

Thanks so much. You are a pro !