Electric Heat

[Jimmy7]

I was asked to replace a faulty 240 volt electric heat wall mounted thermostat, and everything is existing. The heat is fed with 12-2 romex on a 20 amp double pole breaker. There are two 8’ baseboard heaters being controlled by this wall mounted thermostat. Everything is existing and old and has been painted over numerous times. I couldn’t find a wattage on the baseboards, but isn’t it typically 250 watts per foot? If so, wouldn’t this be 16’ x 250 watts =4000 watts, and shouldn’t the breaker only be loaded to 80% (240v x 16 amps 3840 watts)? Instead of 240v x 20 amps= 4800 watts? If I’m correct how would you handle this with a homeowner?

 

[kwired]

I'd just replace the thermostat and move on. Seen similar situation of 16 feet of baseboard on 20 amp circuit many times. Most thermostats for this application are rated something like 22 amps.

 

[rc/retired]

Replace the T-stat. I have the same setup in my house. It's been that way for 47 years with no problems.

Ron

 

[infinity]

If so, wouldn’t this be 16’ x 250 watts =4000 watts, and shouldn’t the breaker only be loaded to 80% (240v x 16 amps 3840 watts)? Instead of 240v x 20 amps= 4800

The 20 amp circuit will likely carry the 4800 watts indefinitely and it definitely will carry 4000 watts indefinitely. So your existing installion although not code compliant will work just fine as it has been.

 

[kwired]

The 20 amp circuit will likely carry the 4800 watts indefinitely and it definitely will carry 400 watts indefinitely. So your existing installion although not code compliant will work just fine as it has been.

Likely carries 4000 watts indefinitely as well

 

[Jimmy7]

Thank you guys for always helping!! Much appreciated!!

 

[junkhound]

Yep, just replace the tstat. Old baseboard came in 2 (or more?) different levels of watts per foot.

Just to satisfy your curiousity as to the load, old baseboard were wired with various different nichrome wire, nearly all of which have near zero resistance variation with temperature. So just measure the dc resistance.

 

[infinity]

Likely carries 4000 watts indefinitely as well

Fixed the typo.

 

[Jimmy7]

I just received the 240v 22 amp wall mounted thermostat from my supplier, and it states “22 amp 240v resistive only in Canada”. Any idea why? Should I return these ones and try to find the same make and model of the one I’m replacing?

 

[infinity]

I just received the 240v 22 amp wall mounted thermostat from my supplier, and it states “22 amp 240v resistive only in Canada”. Any idea why? Should I return these ones and try to find the same make and model of the one I’m replacing?

Who knows why the manufacturer put that on the label but I wouldn't worry about it since you're not installing it in Canada. The UL listing says 120/240 VAC, 22 amps.

https://www.ideadigitalcontent.com/files/11271/ZBR-BSTAT.pdf

 

[Jimmy7]

Okay, thank you! So I’m good to go install it at 22 amps 240 volts.

 

[infinity]

Okay, thank you! So I’m good to go install it at 22 amps 240 volts.

Is your load actually 22 amps?

 

[Jimmy7]

No, what I meant was that I’ll install this 22 amp rated thermostat. In the pictures you can see the amp probe reading from each leg

 

[infinity]

No, what I meant was that I’ll install this 22 amp rated thermostat. In the pictures you can see the amp probe reading from each leg

You're good to go.

 

[Frank DuVal]

Electric baseboard heat is resistive only 99% of the time. (I dropped it 1% due to maybe some manufacturer somewhere added a small fan to their unit?)