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  • Changing 240V to 120V for Baseboard

    Hey All,

    I was wondering if I can change my baseboard heat from 240 to 120?

    THe reason is that I am installing 120V radiant floor heat and had planned to use an existing but unused 240 circuit that had been used for a baseboard heater. I jsut discovered the circuit I planned to use is shared with another 240 V basebaord from another room.

    I don't want to run another circuit and can easily enough convert the line to 120 by changing one fo the hots to a neutral at the breaker panel.

    But I want to know if it is safe to convert the 240V baseboard to a 120V basebaord. It is rated at 240V and 2000W at 8 Amps. So I would wire it as a 120V and 2000W at 16 Amps. Does a baseboard ahve that flexibility?

    Thanks in advance,

  • #2
    Re: Changing 240V to 120V for Baseboard

    Most heaters that were made for 240 Volts can't be changed. If run on 120 Volts nothing bad will happen but they will just get a bit warm and not heat up a cold room. The only way you can make this work is if there are 3 wires and a ground. This would be black and red as hots, white as neutral and bare/green for ground. You might take a look at the wiring to see if by any change that's what was used. If not, then you'll need to pull new wiring or use a step down transformer to convert 240 to 120 Volts. You might look into changing the baseboards to 120 Volt ones but do watch for overloading of the circuit. Can't you get the new heat in a 240 Volt version? I'm sure such is made by one of the major brands. If you can tell more about just what you want to add, maybe I can help with finding such.

    RobRo, You will be far better off if you can run all of your electric heat on 240 Volts. I hope you haven't yet purchased the radiant heat.

    WARNING: Electrical work is not for the DIYer unless he/she really does know how to do the work properly. In addition insurance companies take dim views of non licensed people doing such work. Always try to think about safety.

    UPDATE: This came out all wrong. What I was thinking and what is there now are just not the same. Forget doing anything wild or you'll just end up with a real mess. Please see warning above.
    Last edited by Woussko; 11-25-2007, 12:10 AM.


    • #3
      Re: Changing 240V to 120V for Baseboard

      Thanks for response. Unfortunately I have already purchased adn installed the 120V radiant floor heat. So I am stuck making this work. I am going to call the vendor on Monday to see if the radiant floor heat can be run on 240V instead. It is the only item Lowes/HD carry in stock.The manufacturer does make it in 240V and I was surprised to see they sold it only in 120V. All the baseboards are in 240V. Why does it matter so long as the wattage is the same (2000W)? 120V 8A vs 240V 16A? If the wattage is the same wouldn't the heater warm the same amount?

      I will check the wires, ,it woudl be a great simple solution if they ran a 12/3.

      Maybe I will look into the transformer for this one. Any idea how muhc they cost and how big they are?

      I appreciate the words of caution. I am good at doing my homework to get it right. I have wired enough to be dangerous and usually get an inspector for the big projects.

      Thanks for your help.


      • #4
        Re: Changing 240V to 120V for Baseboard

        No, you can't just change one wire of the circuit to pull 120v off of if you are using any of the 220v baseboard heats.
        IMO you should consult a qualified electrician to do the work you want.

        BTW, you can get 220-240v floor heat systems. But, if you're running (2) 2000w electric baseboard heats that's over 18a, close to the limit of the application of the 12g that it probably is ran in. Again, a new circuit would be your best route. Calling a qualified electrician would be your best AND safest!


        • #5
          Re: Changing 240V to 120V for Baseboard

          Even if they ran 12-3 you're going to overload your circuit. You need a new circuit.


          • #6
            Re: Changing 240V to 120V for Baseboard

            Let's get things straight about the load now. Is there a total of 2000 Watts of heat on one 240 Volt circuit or do you have 2 such heaters on the same circuit?

            Please state exactly what loads (all) are currently on the circuit you have.

            2 X 2000 Watts on 240 Volts = 16.67 Amps and to be safe you really do not want more than 16 Amps of load on a 20 Amp circuit when the load will be on for long periods. Put simple you have maxed out now. If you only have 1 of the 2000 Watt baseboard heaters then you could add more.

            Where is the radiant heat being installed and under what kind of flooring?

            Forget about the transformer idea. It would cost far too much and you really should run a new circuit to the new heating load(s).
            Last edited by Woussko; 11-25-2007, 12:12 AM.


            • #7
              Re: Changing 240V to 120V for Baseboard

              You are WRONG if you think you will get the same heat from a 2000 watt 240 basebord hooked up to a 120V line. The 240 volt basebord will NOT draw 2 times the current and make the same 2000 watts of heat. What WILL happen is the heater will draw 1/2 the current and you will get only 1000 watts of heat. That is the way it works, not the other way round.
              What you could do here is this. I don't know how you buy this floor heating stuff, but you could buy 2 120v sections and put them in seires on the 240 line you have now in the bathroom from the old heater. Lets say you buy the heater stuff in square foot coverage. Instead of buying one set at 100 sqaure feet, can you buy 2 at 50 square feet? Then you put the 2 in series acorss the 240 line you have and problem solved. Lou


              • #8
                Re: Changing 240V to 120V for Baseboard

                Actually I think some of us forgot the power law rule. Where there's a resistive load it's Voltage squared divided by resistance. A heater designed for 240 Volts will only put out 1/4 amount of heat and take 1/4 the power to run it on 120 Volts. I have run a baseboard heater designed for 240 Volts on 120 Volts. It just gets a little warm but is pretty much useless as a heater.

                What needs to be known is if there are 2 heaters of 2000 Watts each on the 20 Amp 240 circuit or is there just one such heater.

                RobRo: Whatever you do don't connect up a 120 Volt (design Voltage) anything to 240 Volts unless you want wild things happening at your place. The only way this could work is if there are 2 elements per heating unit and they are currently connected in parallel. Then if reconnected in series they could be used on 240 Volts. This is where contacting the manufacture will be a good idea, but there should be wiring diagrams with the heaters. As for your baseboard heater(s) please please leave them as is.

                Bottom line: What is currently connected to the present heating circuit? How many and what?
                Last edited by Woussko; 11-25-2007, 02:06 PM.


                • #9
                  Re: Changing 240V to 120V for Baseboard

                  RIGHT Wousko, 1/4 the power. Thats even worse than 1/2 the power. The way I see it, the easist way is to put 2 120v heaters in series or just get a 240 heater strip. I think he said it is already installed and may have already installed the concrete over it.


                  • #10
                    Re: Changing 240V to 120V for Baseboard

                    You guys are getting way over the head of even a homeowner/diy-er with above average electrical knowledge.

                    RobRo, call a qualified electrician. Make sure they're licensed and insured.


                    • #11
                      Re: Changing 240V to 120V for Baseboard

                      Originally posted by GilBeQuick View Post
                      RobRo, call a qualified electrician. Make sure they're licensed and insured.
                      Very good advise