How to completely shut off 120v electric baseboard heater?

1229 Views 8 Replies 4 Participants Last post by Nealtw, Mar 1, 2020

Grobierno

Discussion Starter · Feb 29, 2020 (Edited)

I've planned a 20A circuit serving a tiny half-bath in a workshop. The circuit will contain a few LED ceiling lights, a receptacle (not for tools) and a 400W 120V baseboard heater. So it would not be convenient to shut off the heater via the breaker in the main panel. When I'm not working during the winter I expect to occasionally winterize the bathroom (regarding water) and would want to completely shut off the heater. I understand that a single pole-thermostat with a 120v heater does not completely cut power to the heater in that the thermostat is always able to send power if activated by temperature.

I'm trying to understand:
1) if I can use a double-pole wall mount thermostat that feeds the heater. I understand this is primarily for 240v heaters so there is a pole for each hot and one pole is actually switched. I have found a little info on using them with 120v but it is confusing me.
2) if not, could I mount a single pole thermostat on the heater then install a typical single pole wall switch before the heater.

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CaptTom

· #2 · Feb 29, 2020

I have a thermostat in my barn "office" that feeds a 120VAC outlet that I plug a small heater into. It's a re-purposed 240VAC thermostat, but has no problem with 120V. It is the old-fashioned dial type which goes all the way down to "off," where it is most of the time.

A quick Amazon search found this one:

A 400W baseboard seems a little odd. A $15 plug-in heater from WalMart will put out 1,250 to 1,500 Watts.

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CodeMatters

· #3 · Feb 29, 2020

Grobierno said:
I'm trying to understand:
1) if I can use a double-pole wall mount thermostat that feeds the heater. I understand this is primarily for 240v heaters so there is a pole for each hot and one pole is actually switched. I have found a little info on using them with 120v but it is confusing me.

Yes, you can do this. Voltage and current of tstat must meet or exceed
that of the heater. In your case you'd have a hard time finding one that
isn't suitable.

Use a large/deep box.

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Grobierno

Discussion Starter · #4 · Feb 29, 2020

Thanks CaptTom and CodeMatters!
Coincidentally, the tstat CaptTom shows is the one I recently purchased. I attached an image of part of the instructions, No other notes were included, written or graphic, regarding actual wiring. To review, I want to install a hard wired 120v 400w electric baseboard heater with a tstat and be able to completely cut power without using circuit breaker. CodeMatters, i was confused by the Honeywell diagram. To my untrained eye the left figure looks like 240. Is the right figure for 120, using only one of the two poles? If so, does L2 stand for one of the hot legs of 240 in the left figure, but in the right figure stand for the neutral of 120? This is where I became confused. If this tstat can be used in double pole configuration (so I have a positive off) for my 120v heater, can you show me a wiring diagram or clarify the left figure in the attachment?

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Nealtw

· #5 · Feb 29, 2020

Just treat it like a light switch, just switch the power wire and join the neutrals.

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CaptTom

· #6 · Feb 29, 2020

You are correct. Use the right-hand diagram. L1 is hot (the black wire) and L2 is neutral (the white wire.) If I'm reading this correctly, the stat will always have power to it (unless you open the breaker) but dialing it down to "off" will turn off power to the heater.

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Grobierno

Discussion Starter · #7 · Mar 1, 2020

Got it Capt. I think I should return the wall mount double pole tstat, and get an onboard single pole tstat when I buy the heater. Then, in order to be able to completely cut power when needed, I can use the switch box I originally installed for the wall mount tstat, for a single pole wall switch that feeds the heater with its onboard tstat.

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CaptTom

· #8 · Mar 1, 2020

I keep wondering why all the effort for what you say is a 400W heater. I'd just buy a $15 plug-in heater with a thermostat right on it. Those will put out anything from 750W to 1,500W.

Admittedly, I got fancy and put a thermostat on the wall, controlling the outlet I plugged the heater into. But that's because it was a new build and I had an old line voltage thermostat hanging around anyway.

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Nealtw

· #9 · Mar 1, 2020

Grobierno said:
Got it Capt. I think I should return the wall mount double pole tstat, and get an onboard single pole tstat when I buy the heater. Then, in order to be able to completely cut power when needed, I can use the switch box I originally installed for the wall mount tstat, for a single pole wall switch that feeds the heater with its onboard tstat.

That double has an off position, when turned off the outlet will be just like any light with the switch turned off. Then if you want to make sure when you play with the heater you can always unplug it.

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