I have existing aluminum wiring, previously used for an electric stove top, that I would like to repurpose for a sauna heater in my basement. The electric stove top is gone.
Heater Specs from the manual:
6Kw, 240v/1ph, 25 Amps, 10 Gauge Wire
Indicates to use copper wire rated for 90 degs C
The existing wire circuit has a double-40 amp breaker using #6×4 conductor XHHW-2 alumiflex.
Distance from the breaker to the heater will use around 60 ft of wire.
Will it be safe and within specs to do this?
Thanks!
Best Answer
Honestly, you're probably better off leaving 40A service to an electric stove in place. It's a selling point when you go to sell the house, especially when it's a competent 4-wire circuit, for people who might want to go back to electric, or do a best-of-both-worlds gas range and electric oven. Since it also has gas, that takes the sting out of the aluminum wire for those who are bothered by #6 aluminum.
If it's convenient you might drop #8 aluminum or copper straight down from the stove receptacle to the new appliance. You need to make an Al-Cu transition anyway, inside the stove box is as good a place as any.
A 6 KW heater is 25 amps. That must be derated by 125% to 31.25 amps. You cannot put 31.25 amps on a 30A circuit unless the device is UL-listed and the UL-approved instructions tell you to do that. If they do, feel free to use #10 copper for the final-run to it.
You cannot put aluminum wire on the device's terminals; they are not listed for AL. So you must pigtail with a legal size of copper wire. You can splice from #6 Al to copper with a "MAC-Block" insulated splice, inside a junction box. That may require mounting an additional junction box. See how that's enough trouble that you might be better off just making that splice in the oven box?