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Thread: Wiring baseboard heaters

  1. #1

    Default Wiring baseboard heaters

    does anyone have, or can explain how to wire two separate rooms each with a heater and individual t-stat, both going back to the same double pole 20 amp breaker on the same line?

  2. #2
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    Assuminf that the heaters are 240 volt units, the basic idea is this: the 240 would go to a junction box somewhere, and from that box, two cables would run, one to each thermostat. The rooms would work independent of each other.

    Are you sure that a 20 amp breaker will support 2 heaters? Each heater would need to be probably a max. 1500 watt unit. Ideally, you should not run two 2000 watt units off one breaker.

  3. #3


    I know that here in this house, the electrician wired it so that one 12/2 wire was run back to the panel box. That 12/2 was for 2 heaters and 2 t-stats.
    I know he didn't overload the circuit.

  4. #4


    So, how do I tire the wires together? Panel box to one- 12/2 wire.. and then? How do I connect the T-stats to this?

  5. #5
    ACO Shower Drain Sales johnfrwhipple's Avatar
    Join Date
    Jul 2009
    North Vancouver, BC
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    Default Baseboard Heaters

    For the record I'm not a ticketed electrician but we have done this many times.

    Your electrician most likely measured the room size for each room being heated and calculated what the right wattage output for each heater should be. Assuming his math was right he then calculated that a 12/2 wire was OK.

    This doesn't seem wrong as many jobs we have done we have had multiple baseboard heaters running of one 12/2 wire.

    You have two thermostat locations. The wire from the panel will run to one of them. There should be in one thermostat location 3 12/2 wires in the other 2.

    The one with 3 12/2 wires need to be sorted out if they are not all ready labeled. you need to be able to check for continuity of the 12/2 lines. With the power off of this circuit twist the 12/2 wire coming out of the wall for the baseboard heater toghter and go back to the thermostat location and find which one of the 3 12/2 wires tones or beeps. This is your 12/2 feed leg to the heater. The remaining 2 are a jumper to the next thermostat and the feed from the main panel. Leave the wire that powers the baseboard heater untouched and twist toghter the remain two wires with an extra pig tails for the thermostat. Cap these 2 pig tails with merrits and go to the next thermostat location.

    There should only be 2 wires here. separate the two and put the breaker back on to see which wire is hot. Label and switch the power back off.

    You now have 2 pigtails capped at one location and the second location labeled. These 2 sets of 12/2 wire represent the power from your panel (your line voltage 220). Your thermostats will be labeled with instructions on how to hook them up. Which wire goes to line which wire goes to load etc.

    Make sure you have your tester and make sure you where your safety shoes or boots. Have the city inspector come by and check the final job for peace of mind and remember that only a liscenced electrician can work on heating needs for a rental unit or basement suite...

    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  6. #6
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default heaters

    You are not going to like this reply, but if you do not know how to make these connections, since they are the most elementary, and intuitive, ones in the business, maybe you should not be doing this project.

  7. #7


    20A dbl pole breaker connected to 12/2 which goes to a junction box. Junction box then feeds a 12/2 to each T stat. Therefore the J box will have 3 12/2 wires connected to it and each other. Each T stat now connects the load side to the heater with 12/2.

    Take out a permit and get the job inspected.
    My answers are based mostly on the ICC codes. Advice given is my personal opinion and every person performing work should acquire a permit from his/her jurisdiction and get the work inspected. My opinions are not directions to follow for DIYs or professionals


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