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Honeywell Wi Fi Color Touchscreen Programable Thermostat RTH9580

I replaced an older programmable thermostat with this one as the older one would not shut the boiler off. The boiler is a Mini Star 30KW by Super Hot. Yes it is too big for my house but it has three stages so it does not run full tilt unless it is very cold out. With this fall weather, mostly the one stage with a few jumps up to the second stage. The thermostat seems to be holding a very constant temp in the house. As far as I can tell, it is working better than I expected. So my question, The thermostat shows outdoor temp (from the WiFi). Is the thermostat using this as a outdoor reset to control the supply temps? I have the boiler supply max set at 110 and it seems supply temp very rarely reaches this temp. Sometimes when it calls for heat, the supply temp can be as low as 80. Only the first stage of the boiler running. Dont get me wrong. I am very happy with this. In the manual it said that this thermostat will learn your system. Just trying to figure out if I have chosen the perfect thermostat for my system.


  • njtommy
    njtommy Member Posts: 1,105
    edited September 2016
    The T-stat will stage your boiler a couple of ways.
    It will go to 2nd or 3rd stage depending on space temp and how many degrees it is off of set point. Like 65 in the house and t-stat set to 70. This works well for night set back or your recovery times.

    It will also bring on all your stages depending on if you have the t-stat set to bring on all stages of heat at the end of each heating cycle. Most likely not in your case.

    I'm not sure if your t-stat will do this like the Honeywell prestige will basically the same looking t-stat. But the -t- stat will bring on stages of heat depending on run times. So if the boiler runs for 20 mins non stop it will bring on second stage. So it basically times staging. But this I believe is a setting in your t-stat when it's programmed.

    Not sure if your t-stat has Data log or a performance log but that tracks all the info from your t-stat including out side temp, inside temp, and run times for each stage.

    You can call and ask Honeywell they have great tech support.
  • ricking
    ricking Member Posts: 34
    Thank you sir. Good info.
  • John Mills_5
    John Mills_5 Member Posts: 950
    Never heard of them using outdoor temp reading as boiler outdoor reset. Other than telling you the temp, only thing I know its used for is dual fuel applications.