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  • Baseboard Wiring Question....

    I'm finishing my attic and I'm installing baseboard heating. So far I've learned; there are 2 hots, no return, you can wire 16ft of baseboard heat to a 20amp breaker, I know my thermostat options, etc....

    My question is this, where there are 2 hots and no return, do I wire the panel any differently?

  • #2
    Re: Baseboard Wiring Question....

    Nope you just need to install a 2 pole breaker (a 240volt breaker) and put one wire under each screw of the breaker and put the ground on the ground or nuetral bar where the rest of them are.

    I have to say as well, 16 ft. is a lot of baseboard heat to put on a 20 amp breaker. Baseboard heat is 250 watts per linear foot. So 16 ft. equals 4000 watts, divide that by 240 volts and you get 16.6 amps. Now you need to multiply that by 125% because it is what is considered continuous duty (means it is possible for it to be turned on for more than 3 hours at a time) and now you are at 20.8 amps ona 20 amp breaker. The 20 amp breaker will never hold that. Either run it in #10 wire and put it on a 25 or 30 amp breaker, or divide the circuit in half.


    Last edited by piette; 01-25-2008, 11:32 PM.


    • #3
      Re: Baseboard Wiring Question....

      Check the baseboard heaters as some run at about 188 Watts per foot but the normal for 240 Volt rated ones is 250 Watts per foot. As stated if you want to use 16 feet on one circuit and it is 250 Watts/foot then you really need to go for #10 copper wire.

      This is something people forget but if you use 12-2 or 10-2 (with ground) normally you have a black and white and bare conductor. Please for safety reasons do not leave the white wire white if it's connected as L2 hot. Put red tape on both ends. You don't want to have anyone confuse it with neutral.

      If you do need 4000 Watts of heat for one large room, you may want to considder a fan forced wall mount heater or two of them at 2000 Watts each with built-in thermostats. It's less work and forced moving air gets the heat around the room faster. Just something to think about. I would try to go with 3000 Watts of heat for this room and see how it works out. If that just won't heat up the place chances are you'll want 5000 Watts or even more and that means 2 circuits in most cases. There are commercial unit heaters but I really doubt you want such in a house you live in.

      This may seem crazy but please think about it and discuss it with a local electrician as this is not a DIY job. My idea is that it seems like you have a finished attic you want to heat and that means other electrical needs as well. My thought is to run 6-3 with ground and connect it up to a 2 pole 50 Amp breaker. Then in your attic have a 8 space sub-panel. Now you can have 2 heating circuits. 1 lighting circuit and 1 receptacle circuit, and if you want to install a good size window AC later you can add another 15 or 20 Amp 240 Volt circuit for it. Be 100% sure not to have the heat and AC run at the same time. In the summer it would be good to shut off the circuit breaker(s) for heating and in the winter shut off any that are for AC. I know this may seem wild, but in the long run I bet you'll be thankful to have 50 Amp service and the sub-panel in the attic. If not for just the attic it helps for adding a circuit in a room below.
      Last edited by Woussko; 01-26-2008, 05:04 AM.


      • #4
        Re: Baseboard Wiring Question....

        Thanks guys, any advice is greatly appreciated...

        I've been doing a lot of reading. I read about the 16ft per 20amp circuit here >

        If you’re interested, it's about the 7th paragraph down. I guess you can't believe everything you read....

        I'm finishing the attic pretty much from square 1. I ran the ceiling joists, installed that recessed lighting, the outlets and have most of the insulation up (foam vents etc).

        I already ran a sub panel up from the basement. It has 8 circuits. The attic is about 15ft by 50ft. I figured on 2 circuits for the heat (2 sets of 8ft baseboard. 1 for an AC, and another for the bathroom. I already had 2 extra circuits (outlets and lights) running up to the attic from the main panel when I moved in.

        How many watts do you think I need for a space this size? And if I use 10-2 wire, How many feet of baseboard could I go with? I considered a fan heated and will probably use one for the bathroom, but I like the quiet of baseboard.


        • #5
          Re: Baseboard Wiring Question....

          Unfortunately I don't have any of my books with me and I can't remember the number of watts per square foot you need for heating.. I am at the hospital, my mom is battleing Luekemia, so my books are at home.

          As far as the 10-2 circuit goes it is pretty simple. Take the number of watts (250 per ft.) and divide by 240 volts. This will give you the straight amperage. Now multiply that by 125% for continuous duty. You don't want to go over like 21 or so to use a 25 amp breaker or 26 to use a 30 amp breaker.



          • #6
            Re: Baseboard Wiring Question....


            I hope everyone that reads this thread will pray for both you and your mom.


            • #7
              Re: Baseboard Wiring Question....


              With the sub-panel installed it would seem you're all set nice there. On a 20 Amp circuit which would normally be #12 copper wire you can safely go with 15 feet of normal 250 Watt/foot baseboard heat on one circuit. On a 30 Amp circuit which would be #10 copper wire you can go with up to 22 feet.

              It's a good idea to check the actual Wattage rating of the brand and type of baseboard heat you plan to install. Some companies don't totally follow industry standards. I understand about not wanting fan noise. If you really want nice heat and quiet, you may want to considder going for a lower Watt density type that run around 185-190 Watts per foot. In many cases it will be rated for up to 277 Volts at about 250 Watts/foot and then lower at 240 Volts and lower yet on 208 Volts. If you have room along long walls it's nice not to have the really hot elements and hot cases. All get hot, just not as hot.

              You might take a look at this .PDF file and also prowl this web site. This company is huge into electric heat. I recommend going to the main home page and clicking on the HEATERS tab and just prowling around. To read up on a given model series look for the link called Bulletin and click it. That will get you a .PDF file with specs and model numbers.
              Whatever you do, don't buy the junk grade from Home Depot or Lowes. They make heat but also in many cases go bang bang bang heating up and cooling down. Also, they won't last near as long as good quality products. If you want something really nice, look into the electric-hydronic baseboards. With a good thermostat they will stay warm rather than switching from real hot to cool to hot again.

              As for trying to figure out how many Watts of heat you need, there are just too many variables. You would do well to go with two circuits and have two thremostats. In mild weather you may only need to use 1/2 of the heaters. Do be sure to get good quality wall mount thermostats with heat anticipators so you don't have wide temperature swings from on to off to on. on to on.

              Special note: Very few built-in (mounts in baseboard and are junky) or wall mount thermostats have switch contacts heavy enough for use on circuits above 20 Amps. They may be rated at 22 Amps but that's the max it can withstand. Like the circuit it's wise to have a safety factor. With this in mind, think about 2 circuits. You might install both wall thermostats near each other and do a split-up overlaping heater layout. This would be where thremostat A operates one baseboard near each end of the attic and the same for thremostat B. This will take more work wiring it up, but the idea is to have circuit 2 as a booster for circuit 1. You would place the baseboard heaters for circuit #1 under windows and in areas that really need heat. Then circuit #2 could have them located where it's less work for you overall.

              Main site:
              PDF files on baseboard heat:
              Attached Files
              Last edited by Woussko; 01-27-2008, 02:02 AM.


              • #8
                Re: Baseboard Wiring Question....

                Thanks guys, really, a huge help.

                Sorry to hear about your mom Piette, there are a lot of services out there for berevement, I actually work as a psych clinician in an emergency room, so I often help people out with this kind of thing.

                If you or your family need support, don't be shy in calling your local health center. I often refer to The Center for Greif and Healing, Danvers, MA (978) 223-9737.

                Good luck and thanks for the advice....


                • #9
                  Re: Baseboard Wiring Question....

                  You did not say how high your ceiling was. If it is at least 8' you might you might want to look into Comfort Cove Radiant heaters.
                  They are like a baseboard heater but they are mounted high on the wall and require less wattage. The other advantage of this heater is since it is mounted high on the wall, you won't be blocking them with your furniture.


                  • #10
                    Re: Baseboard Wiring Question....

                    I would think the last thing you would want to do is raise the heat higher on the wall. The heat rises and the lower the better since you are living in the lower area. That is a big problem with cathedral ceilings since the heat rises to the top and one of the main advantages of in floor radiant since the heat stays lower. Lower wattage is just less heat, with electric heat it is all close to the same for efficiency.
                    Last edited by bluecon; 02-29-2008, 03:54 PM.