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Thermostats and outdoor resets

Champ6 Member Posts: 19
Just a homeowner here ( with some steam locomotive experience!) who has questions on controlling our temperatures, especially of somewhat mild days, as is becoming more common.

Our Weil McClain gas fired steam boiler was installed about 10 years ago, replacing an ancient oil burner. The installer is from Chicago and has lots of experience with steam, but moved down here to Asheville to get away from winter. Back in the day with the 'old dragon' boiler, we switched to a programmable thermostat from Lowes.. just a basic Hunter I think. We were both working, so it was nice to cut back fuel use during the day. Now my wife is retired, and we don't change the settings much.

Ever since we got the new boiler, the interior temp overshoots, especially on mild days. Since we also have a heat pump for central AC, we've been using it on these days, but I'd rather use steam, so it's time to address this finally. The old Hunter T'stat does not have much in the way of an anticipator, so what is a good t'stat for steam? Would an ORM also be beneficial in reducing overshoots?



  • Champ6
    Champ6 Member Posts: 19
    One more thing: we have a separate thermostat for the heat pump. Is there a single thermostat that will work, including a choice of steam or electric heat (should the boiler be down)
  • mikeg2015
    mikeg2015 Member Posts: 1,187
    Honeywell pro series l T6 will work and you use a separate “R” for each System. T6 can Take an outdoor sensor and do dual fuel.

    Bonus it has adjustable cycles per hour rather than a fixed differential like the cheap thermostat you have now. Boiler should be 1 or 2 CPH. Heat pump 3.

    You can configure it non programmable too. Most of our customer prefer that.

    Warning the outdoor sensor MUST have a dedicated 2 wire connection other wise to will get interference on the signal and not work. Trust me.

    Supplyhouse.com has them. I think for dual fuel you need the more expensive version.
  • Champ6
    Champ6 Member Posts: 19
    2H/1C means 2 heat sources and one cooling? And is the sensor also a good idea? which one?
    HVACNUT Member Posts: 5,026
    edited October 2019
    The T6 model(s) you're looking for are the dual fuel TH632OU or the TH622OU. You need 3 heat, 1 cool. Heatpump, Aux. and steam. Reliable at a good price. The Prestige line is a nice thermostat but pricey. Worth it IMO. You wont find either at a box store. Try www.supplyhouse.com .
  • Champ6
    Champ6 Member Posts: 19
    Is the outdoor reset a good idea though? Or just a better thermostat?