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electric radiant heat (ceiling) thermostat

sachimay Member Posts: 3
I own a house built in 1961, it has radiant heat in the ceiling, the thermostats we have (Mears M602 Double Pole) don't seem to work well with our system. I will set the stat to 65 and put my son to bed, then last night for example, he was coughing so went into his room and it was nearly 90degrees. It seems to be either all on or all off. There are some clicks we hear which seem to turn it on or off, but is there a better thermostat we can get or are they perhaps adjustable or hooked up wrong.....

any assitance or suggestion on replacement thermostats would be great....

Also, I have no idea what the voltage is for my heat, does that matter or will any thermostat work with it?


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    Yeah, that is a problem...

    It works perfectly when you are at "design" condition, but other than that, it runs WAY too hot.

    The problem is that it is depending upon archaic control technology to make it function. It uses a line voltage thermostat that is either on or off, and has no anticipation capabilities. Consequently, by the time the thermostat realizes it should be shut down, the thermal mass momentum of the gypsum is charged up and projectile vomiting BTU's into the room, causing the room to over heat.

    As for replacement thermostats, you must match voltage and ampacity for the connected loads. The bimetal line voltage thermostats do have a lot of slop to them. If in doubt, hire an electrician to do the work for you. You could try swapping that thermostat for one in another room and see if it shows the same characteristics.

    Also, check the insulation in the space above the ceiling. In 1961, the heating contractors knew a lot less about the need for insulation then they do now. Whatever your minimum R value requirement is for our area, add 50% to that to insure minimal back loss to unheated spaces.

    Ideally, there would be a control logic in place that would change the operating temperature of the emmitting surface based on outdoor and indoor feed back. It is technically feasible with off shelf components, but would be tough to retrofit without having a lot of exposed wires running around.

    Best bet is to start low, and go up slow. Once you hit your "comfort" zone, turn it back a bit.

    Most common complaint from radiant heating systems, is discomfort due to over temp.. That is what you are experiencing.

    Great concept, just short some logic.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
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