Can I use multiple heaters with just one thermostat?

multiple baseboards, one thermostat
This diagram from the Baseboard Owner’s Guide, shows how to correctly wire multiple baseboard heaters to one thermostat.

Sometimes we get calls from people who want to know if they can wire multiple heaters to one thermostat. The answer to that question is yes, you can wire multiple heaters to one thermostat — if you’re using 240-volt heaters and a 240-volt breaker. But that doesn’t mean we always recommend it.

Steve in our Tech Support Department says most of the time people want to wire multiple heaters to one thermostat for the sake of convenience. That makes sense if you have a larger room with multiple heaters in it or maybe an open-concept living space where a living room and dining room are one large area. Having one thermostat to control both heaters will work just fine because you’re dealing with one larger space.

It doesn’t work with one thermostat in a bedroom controlling a heater in that room plus another one in a different room. The temperature in both rooms would be determined by the temperate of the bedroom with the thermostat. That just defeats one of the advantages of electric heat: heating rooms independently to maximize individual comfort and minimize the electric bill.

Still reading? That probably means you’re wanting to know how you can hook up multiple heaters to one thermostat. Here’s what you need to know:

Rule #1:

The number of heaters that you can safely wire to one thermostat will depend on the size of your breaker in the electrical box, what type of wiring you are using and the wattage of the individual heaters.

So a 240-volt circuit running on a 20-amp, double-pole breaker, can have any combination of heaters up to 3,840 watts.

For example, using just one thermostat, you can install:

  • Two 1,500 watt heaters, or
  • Three 1,000 watt heaters, or
  • Five 750 watt heaters

This helpful chart provides more information.

Volts 

Size of breaker

Wire size

Maximum watts on circuit

240

20 Amp Double Pole 12/2 with Ground

3840

240

30 Amp Double Pole 10/2 with Ground

5760


Rule #2

All heaters must be wired in parallel. You can either do that by connecting each heater to the thermostat directly, or by connecting each heater to the next — just be sure that each heater is connected to the source wires. (You can also check out the wiring diagram at the top of this post — it shows how to wire multiple baseboards together.)

Multiple heaters
This photo shows how you would connect wires to use multiple Com-Pak heaters to each other. One of the building wire lines (a.k.a. Romex) is going to the next heater, the other is coming from the wall thermostat. The looped copper wire would be connected to the green grounding screw in the heater wall can.

I know that’s a lot to take in. If you’re at all confused, leave a comment and we will get back to you or get in touch with our Tech Support department. They’d be more than happy to walk you through the process over the phone or through an e-mail.

Paul Suarez

Paul Suarez

Paul is a highly caffeinated, uber organized family man that keeps himself busy finding and sharing the stories that make Cadet a great company. When he isn't writing, or shooting photos and videos, you'll likely find him searching for killer deals on Craigslist, playing classic Nintendo games or quoting his favorite movies and TV shows.

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  • selias33

    I am replacing an 10ft old Federal Pacific baseboard (240V) heater in my dining room. It was installed by an electrician in the late 1970’s (before I bought the house). There is a wall thermostat, but only 12-gauge romex is coming into the heater. I replaced and wired a 6F1500W (cutting only one of the factory connectors on the left side). Can I simply add a 36” 240V heater from the right side of the one I just installed to the left side of the 36” one by wiring directly using the wires in the heater and adding a ground wire between them?

  • Jeremy

    Hi – I have a three season room that I’m placing some baseboard heat in – Based on my calcs I’m going to use 2 1500 watt and 1 2000 watt heater – I’d like these controlled by 1 thermostat – Am I correct in that this would need a 240V 30AMP breaker? ANd could this load be controlled by 1 thermostat such???

    • Hi Jeremy, Could you tell me a little more about the room you’re heating? 5,000 watts should heat about 500 – 600 square feet of space in most cases. You could need more or less than 10 watts a square foot depending on factors like your insulation. You are correct that a 240-Volt 30-AMP breaker will work for these heaters but 5000 watts is too much heat to be controlled by one line-voltage thermostat. You could look into using a relay and low-voltage thermostat to control those heaters. For some more information on that, please call our tech support team: 855.223.3887.

      • Jeremy

        Hi Lena – Sure – So I’m looking at heating a 3 season room – The room is over a deck – 1 side is connected to the house, the other 3 are outside walls (so this is really an outside room on top of a deck)- In addition there is a twelve foot ceiling with insulation – There are a total of 7 exterior windows – The rooms dimensions are 15 1/2 X 12

        • Thanks, Jeremy. That information helps a bunch. What’s the climate like where you are? Keeping in mind the 186 square feet, higher ceilings, 3 outside walls and limited insulation, you’ll need about 1,500 – 2,000 watts to keep your room warm. If you’re in a colder climate then we’d recommend sticking closer to 2,000 watts. That wattage will fit onto your 240-volt breaker and on most thermostats. If you have the room, we recommend you use two 1,000-watt baseboards hooked up to one thermostat. If not, a single 2,000-watt baseboard should do the job too. We would also suggest an electronic thermostat, like this one: http://cadetheat.com/products/thermostats/TH115, because it is going to be more accurate than a mechanical thermostat. We hope that helps, and if you have any further questions, please let us know.

  • dcstaley@hotmail.com

    Hi. I have a four room and 1 bath apartment. Each room is approximately 120 square feet. I have ample pace on my electric panel for whatever is needed. Can my licensed electrician connect all of the baseboard units to each other and then to the thermostat? If so, what size units, wires, etc. will I need.

  • Richard Ryan

    I have built three small rooms in my basement. Each room is approximately 100 sq ft or less. I’d like to use three 1000W heaters each with their own built in or external thermostats. If I use one 20Amp 240V breaker with 12/2 will this be sufficient for all three without overloading? How is the best way to wire each from my breaker source? I’d like to bring my source to the middle of the basement into a junction box and than run a line to each room from there. Does this sound correct?

    • Richard,
      Thanks for reaching out. Our tech team says that a 20-amp, 240-volt breaker with 12/2 wire will be perfect for this installation. As far as how to wire, you have two options:
      1. Run wires from your circuit to a junction box and then run wires to the three heaters from there.
      2. Run from the circuit to the first baseboard, then to the second, then the third. Just be sure to install them in parallel.

      We’re in the process of updating our baseboard owner’s guide with better instructions on how to wire multiple heaters on one circuit. I’ve posted a screenshot of that section since the PDF isn’t on our website just yet: http://cadetheat.com/blog/wp-content/uploads/2017/04/multiple-baseboards.png

      If you have any questions, please reach out to our tech support team: http://cadetheat.com/support/customer-service

      • Richard Ryan

        Thanks Paul. Very helpful.

        • Happy to help. Please let me know if you have any other questions.

  • joshgrimes

    Paul,
    I’m remodeling a studio apartment and installing baseboard heat. Since it’s an open floor concept I wanted all heating units on one thermostat (with the exception of the bathroom, I ran a direct line to that). Because of the size of the space the number of necessary heaters (and wattage) was in excess of what your chart recommended for 12/2 wire but fell easily in the 10/2 30 amp range. I ran 10/2 wire to all units (starting with the t-stat) but now I’m having trouble finding a thermostat that can handle 30 amps. Any recommendations?

  • Gregory Malcolm

    I did an upstairs renovation where I turned 2 rooms and a bathroom into one larger open concept master bedroom. I want to wire 3 baseboard heaters to one single thermostat. The easiest way for me to do that is to send the wiring from each heater straight down to the basement.

    My question is regarding the wiring of the heaters to the thermostat. My thought is Ill install the thermostat in a central location on the upper floor, wire it to the basement panel. Send another 12/2 wire from the thermostat to a junction box back down in the basement. Then send the wiring from each of the heaters to the junction box and connect them all together.

    Would that be ok? My thought is that the thermostat will turn on all 3 of the heaters that way, and of course turn them all off.

    Thoughts?

    • Gregory,
      That’s a great work around. If you have multiple heaters in one room, having them all connected to one thermostat makes a lot of sense. Just be sure that your junction box is large enough to make all of the connections and that the circuit breaker and thermostat are rated to handle the load of all 3 heaters.
      If you have any more questions on the specifics, our tech support team would be happy to walk you through the process on the phone or online.

      • Gregory Malcolm

        Thanks for the reply Paul

  • Gods Savior

    Hi Paul, nice site…
    I remodeled and converted a family room to a bedroom. It is an old house. There is one (apx 6ft) 50,000BTW Gas wall heater sharing a common wall, with one thermostat. Question is, can I replace the existing 50Kbtu with two (6ft) wall gas 35,000BTU in the same opening sharing the same exhaust. I will have to have a custom 2:1 exhaust made(easy) into the existing 4″ oval exhaust. This will allow privacy (I can see and hear through the existing one) and will also allow a thermostat in each room. I’m considering Home Depot Williams 35,000(or 25,000)

    • Sorry we didn’t get back to you for a few days. We can’t advise you on the specifics of products that aren’t our own. I’m curious though, how large are the rooms that you’re heating? That seems like a lot of BTUs.

      • Gods Savior

        The (new) Bedroom side is 12 x 13 x 9ft ht. The dining room side is 14 x 17 x 9ft ht which is open to a similar size living room. I know it is imbalanced that is why I would like two separate thermostats, again, a 100yr old house, inefficient layout. Bottom line is sharing the “proposed new” 4in oval exhausts into the existing single 4″ oval exhaust. Maybe it is best to just put a single electric wall heater on the bedroom side and put a 35,000BTU single sided replacement on the Dining room side.

  • pwo511959

    I AM GETTING READY TO WIRE IN 3 BASEBOARD ELEC HEATERS IN MY HOME. IM LOOKING FOR AN ELEC. DIAGRAM OF SORTS TO GUIDE ME THRU. 240 FROM THE PANEL WILL GO DIRECTLY TO THE WALL THERMOSTAT.. WHICH WILL CONTROL THE FIRST TWO HEATERS ONLY.. THEN i WANT TO JUMP INTO THE NEXT ROOM AND INSTALL A SMALL ONE IN THAT ROOM.. AND THAT ONE WILL HAVE AN
    ON BOARD THERMOSTAT iM AWARE OF THE AMP LIMITS ON THE HEATERS.. WOULD JUST LOVE A DIAGRAM TO PRINT OUT AND FOLLOW

    • Thanks for the question. We’re having Steve from our tech support department reach out to you through e-mail. It may be best to have him walk you through this over the phone. This post is on our short list to be updated with more diagrams, visuals and a how-to video.

  • grad

    hi I’m planning to have 4 baseboards 1500 w each on a 600 Sq ft basement what options do I have to control them can I have 2 thermostats side by side one for the left 2 and one for the right 2 or is this against code also is there a thermostats big enough to handle this load
    relay or contactor not an option for me
    thanks for your time

    • Thanks for the question. You can get away with using two thermostats for this install if you’re using 240-volt power. You’d have two heaters on one circuit, controlled by one thermostat and another two heaters on a second circuit, controlled by a second thermostat. Just make sure that the thermostats can handle 3,000-watts of power each. You can install the thermostats side by side if you like.

      We always suggest you go with electronic thermostats for better comfort and to save a little energy.

      If you’d like a programmable thermostat, we’d recommend the TH115: http://cadetelectricheat.com/products/thermostats/TH115/TH115A-240-D-B?search=th115

      For a basic thermostat, go with the TH114: http://cadetelectricheat.com/products/thermostats/TH114/TH114-A-240-D?search=th114

      If you have any other questions, please let us know. I’d be happy to connect you with one of our tech support people on the phone, through-email or live chat.

  • joe

    Can i install 2 heaters on one circuit, each with their own built in thermostat? I purchased 2 – 48 in. 1,000-Watt 240-Volt Electric Baseboard Heaters. I have a 12-2 supply connected to a 20 amp double pole breaker. The heaters are going on either end of a finished attic space. I prefer not to wire them together on one thermostat because i really only ever need to keep half that space warm at any given time (one half of the room is a home office – during the day, and the other half is a guest bedroom that we’ll only need to heat at night, occasionally.)

    Should I have simply run two 120v/20amp circuits up there, one for each baseboard?

    thanks in advance.

    • Hi Joe,
      Sorry for the delayed response. I ran you question past Thomas in our Tech Support department. Here’s his answer:

      Yes you can install two basebaords on one circuit and have each one independently controlled, you’ll just need to make the connections on the line side (the line that directly connects to the circuit) of one of the thermostat so each can work independently.

      If you have any other questions, or want more clarification you can e-mail Thomas directly (tjones@cadetheat.com). He also included this diagram, which may help explain what I’m saying.

  • Jay

    It is not necessary to run a wire from each heater unit back to the thermostat. This would create quite a bit of box fill in the thermostat box. There’s no reason they cannot be daisy-chained. It is still a parallel circuit. In order for the circuit to be wired in series, the current path would have to go through the heating element phase-to-phase. No one wires them like that! In any case wiring anything above 24V to ground in a home should be done by a licensed electrician. DIY is great for putting in ceramic tile or some built-in cabinets, but not when life safety is on the line. At least if you’re going to offer DIY advice, it should be accurate.

    • Jay,
      Thanks for brining this post to our attention again. I asked our engineering and tech support teams to review the post and your comment and they say you are absolutely correct. We will update this post.

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