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220V baseboard heater

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  • 220V baseboard heater

    This is in a 1980's apartment building. The baseboard heat is always on except when the breaker is flipped off. I checked the wall mounted thermostat (3 wire r, b, and w) and across the red and black the circuit opens when the thermostat cycles off using an ohmmeter and those two wires out of the circuit. At the heater there is a 12/2 romex coming in (at this point I'm guessing from the dp circuit breaker) as well as a 12/3 presumably going to the thermostat. The way it is wired both legs of the 12/2 (white is black striped ) are going directly to the red and black wires for the heater, but are also wired to the 12/3 wires going to the thermostat. At the stat I get 120v at the red and at the black. I don't know if there is a junction box burried in the wall somewhere, but I doubt it as this place was built to a strict code, but you never know. Other buildings in this complex have the same set up, but at those heaters there is a summer/winter toggle sw. and an outlet that I'm sure is for a window a/c that can be controlled by the wall stat. So, in the unit I'm working, there's no summer/winter set up. I'm thinking that at some point in time a couple of years ago or so, someone took out the switchover panel and put in a plane panel on the heater and rewired the thing for heat only. I have no other idea as to how this could be wired the way it is and be controlled by the thermostat (Mears).
    So, my question is, can I rewire the circuit so I break one leg of the incoming 220 and send it up to the stat and back down via the red and black leads in the 12/3? Is it ok to leave one side of the heater hot and regulate the other side? Knowledge wise, I'm ok with 110v and can get by with most aspects of 220v work, but I'm not sure with this one. Since the power appears to be at the heater and the thermostat is controlled with a 12/3 switch leg I can't do a double pole wiring at the stat, I don't think.
    Thanks, Mike

  • #2
    Re: 220V baseboard heater

    Hi Mike, it appears that the power (12-2) is at the baseboard. Not the usual way to wire, but not illegal. That being said, there should be 4 wires coming in from the thermostat. Actually 2 going out to it and 2 coming back so you can break both legs of the 220V. Since you only have a 12-3 going out to the T stat, you can only break one leg of the 220. So what you need to do is connect one leg of the 220v coming in from the 12-2 to the heater. The other leg of the 12-2 connects on one of the 12-3 wires, make it red. Then at the T stat, switch the red leg through the single pole T stat and return it on th black from the 12-3, connect the black to the other heater wire. You are only breking one leg, but it will work. You should use a single pole T stat. Obviously the white wire will not be used and should be safed off. Lou

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    • #3
      Re: 220V baseboard heater

      Thanks Lou. I'll do just that. I didn't know what would happen leaving one side of the heater hot and interrupting the other, but I thought from other info I gathered I could do that. Really appreciate your input.
      Mike

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      • #4
        Re: 220V baseboard heater

        The basebord will work fine breaking one leg, but the drawback is that someone later on trying to work with it might think the voltage will be off at the baseboard if the T stst is in the off position, when in fact one leg is still hot. Other than that it will work fine. You should really break both leads, but you can't. Someone that knows what they are doing always puts a hotstick on wires before they touch them just to be sure. I am an electrician and I always hotstick my wires before i work with them so i know what is what. It only takes 2 seconds to wand them. SAftey first. Lou

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        • #5
          Re: 220V baseboard heater

          I've run into some "creative" wiring in a number of situations in the past that mandate checking all of the leads in a box to make sure the power is off before I start working in it. Can't say I haven't done some stupid things, but safety, as you say, comes first.
          Baseboard heater now works the way it should. The guy before me, whenever that was, apparently was having a bad day.
          Mike

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          • #6
            Re: 220V baseboard heater

            Mike

            You would do well to put a label on the thremostat cover with the correct circuit breaker number and a warning that the t-stat only breaks one hot side.

            Update: Please see Robert's posting above this one. I do NOT like the idea of ever breaking just one hot side. It's far too easy to get zapped. I'm glad to see the codes address this. I really wish they would demand (I bet some areas do) that for any 240 Volt single phase circuit that the white wire is only to be used for Neutral and thus the need for 12-3 or 12-2 special. The special would not have a white, but rather a black and red with ground. Red taps helps, but people don't always use it or use near enough. What people do and what they should do ____ well you know.

            Mike, With this being a commercial building (correct me if wrong) you might be wise not to touch it. If anything ever goes wrong even if it's the year 2050 someone is going to be wanting your hide. I think it would be wise to correct this all the way with help from an electrical contractor. You really don't want/need to deal with a greedy lawyer later on, or worse yet an angry D.A.
            Last edited by Woussko; 03-30-2007, 07:31 PM.

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            • #7
              Re: 220V baseboard heater

              It is actually required to have a disconnect for the heater, so using a single pole thermo to control it would require the installation of a double pole switch at the heater. Article 424 - Fixed Electric Space-Heating Equipment.
              Licensed Philadelphia electrician
              Philadelphia emergency lighting certification

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