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Why is my radiant heat water hotter upstairs than downstairs?

nickgirard21 Member Posts: 2
edited October 2021 in THE MAIN WALL
Hello, I recently purchased a new home with radiant heat in both the upstairs and downstairs. My downstairs thermometer attached to the circular pump(s) runs at 135 degree which is normal to me, but the upstairs registers at 180 degrees which seems extremely high. Is there a reason behind this and something that I should do to look into it? the systems are both ran off the same boiler which is set to 130 but just want to be sure i'm not at risk of damaging anything as i've never had radiant heat before.
Any help is appreciated.
Thank you


  • Jamie Hall
    Jamie Hall Member Posts: 22,947
    is way too high for a radiant floor -- if that is what you have. But then, so is 135 -- just not as far off the mark.

    So... is this a radiant floor installation, or is it baseboards or conventional radiators? Makes a big difference!

    In any event, there most be a reason for the temperature difference -- if only a wonky thermometer. But before going any farther... radiant floor, baseboards, or radiators? Zoned by pumps or valves? And at least a description of how it's piped -- better yet, a few photographs would help a lot.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • nickgirard21
    nickgirard21 Member Posts: 2
    Two pictures attached are the mechanical rooms, the upstairs is now down to about 120 and the downstairs at 140. This is the first time we have turned the heat on at all this year and in this new house, so i'm wondering if it was just initially heating which is why it was running higher? It is a fully radiant floor installation, home was built in 2001-2002. No baseboard or radiator. there are 4 zones downstairs (including the garage which is not on) and 5 zones upstairs (every room, but only 3 of them are currently "on" As I mentioned i am new to radiant heat so not sure the most practical method of using it. Thank you!

  • Jamie Hall
    Jamie Hall Member Posts: 22,947
    I think what I was really looking for was photos of the piping and arrangements around the boiler... in any event, I can't access those photos.

    Most radiant floor installations use water at no more than 110 or so so as not to overheat the flooring materials -- or the people walking on them! And, also normally, the arrangement is that the water is circulated in the zone loops by a circulating pump. Some of the water does return to the boiler, but some of it is returned to the loop before the circulating pump by a mixing valve which controls the water temperature in the loop. That valve, in turn, in the best installations is controlled by outdoor air temperature -- called outdoor reset -- but I expect given the age of your system that what happens instead is that the valve position is fixed and a room thermostat turns the circulator on and off to control the space temperature.

    It is possible that a simpler arrangement -- without the mixing valve -- is used. But I'd need to see the piping arrangement near and around the boiler. It is even possible that there are mixing valves, and that they are set for the temperatures you are seeing -- but that the circulation is on only for very short periods of time to avoid overheating the floor.

    Bottom line -- need to know a lot more about the system and how it is piped and controlled.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England