2 wires for my thermostat?

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  • This topic has 3 replies, 4 voices, and was last updated 21 years, 3 months ago by Avatar photoNOS Plumbing and Heating</titl.
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    • #278302
      Avatar photoMasterPlumbers
      Keymaster

        hi all,
        installing a new thermostat (LUX 500) and I’ve only got 2 wires from the old thermo…I hook them up and get the furnace to fire and blow hot, but I don’t seem to have any control over it. I crank the heat and it blows hot but then I lower it to 15 degrees, but it still blows HOT air? wazup with that?

        cheers,
        marc

      • #298241
        Avatar photoSelgas
        Participant

          Still blows hot air after the thermostat has closed off??? You sure you are not just getting the residual heat from when the burner was firing up. You may have a lowering setting on your system as well – it would help some if you were to tell all of us poor Plumber fellas what exactly you have there – after all we are not mindreaders although a lot of our customers think we are!



          Selgas Services Ltd
          Craftsman Gasfitters, Plumbers, Electrical Service Technicians

        • #298242
          Avatar photonicktheplumber
          Participant

            It sounds like your thermostat is telling the furnace to provide heat no matter what you set the dial to. You need to remember that the thermostat is basically an on-off switch that opens or closes depending on the ambient temperature (at the thermostat). The kind of problem you describe is due to one of two things: 1) the thermostat is faulty; or 2) the gas regulator at the furnace is faulty. There is a third possibility, that the wiring between the thermostat and the rgulator is shorted, but that’s unlikely and easily checked with an ohm-meter.

            You need to tell us whether your regulator uses a millivolt thermopile or low voltage current through a transformer. This gets a bit complicated for the layperson. I could suggest a few procedures to fix your problem, but at this point I recommend that you have a licensed HVAC professional check out your particular system. It shouldn’t cost you much.

            NtP

          • #298243
            Avatar photoNOS Plumbing and Heating</titl
            Participant

              do you have a coelman furnace b/c they use a scrud up sistem, it involved about 10 different parts thru out the furnace that it does not need

              is it a other traler house furnaces are like that and some houses to.

              make sure your therm is a heat only thermistat.

              do you have cental air, using the furnace blower???

              you could test your new therm with a Ohm meter.

              reply with answered ?’s and we can help u more.

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