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Smart stat and hydronic heat

Gta
Gta Member Posts: 133
edited February 2020 in Radiant Heating
Hi folks

What smart stat would work best for radiant heat? Are there any to avoid? I’m looking at getting all 3 replaced in my house thx Sean

Btw I’m currently running the rehau dual sensing digital ones

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 17,049
    By radiant heat, do you mean a radiant floor or radiant ceilings? If so, the response time of that type of heat to changes in thermostat settings is on the order of many hours to days. I cannot recommend using a smart thermostat which is allowed to ask for setbacks on lack of occupancy, or even overnight, for such applications.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Jean-David Beyer
  • Gta
    Gta Member Posts: 133
    Radiant floor
  • Jamie Hall
    Jamie Hall Member Posts: 17,049
    Gta said:

    Radiant floor

    A radiant floor takes hours to days to change the space temperature. They are great at holding a constant, comfortable temperature.

    Therefore, I honestly don't know what a "smart" thermostat is going to do for you.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • nibs
    nibs Member Posts: 462
    Thin slab radiant floor with lots of thermal mass.
    Turned down the thermostat to 50 Deg F when leaving for the south for 3 weeks mid Dec, took six days for the boiler to light up at 50 Deg.
    On our return took 2 days to bring house back to 70 +/- on our return.
    Set it and forget it unless you will be away for a week or more.
  • Gta
    Gta Member Posts: 133
    Thx for the input....
  • Gta
    Gta Member Posts: 133
    I just honestly don’t like the rehau stats ...they turn on the boiler with barley any temp drop... I was hoping the smart stat could allow me to adjust it ...
  • Jamie Hall
    Jamie Hall Member Posts: 17,049
    The best setup for a radiant slab, if your system has the option, is going to be primary/secondary, with the secondary always on and a mixing valve controlled by outdoor reset and a floor sensor. The boiler would then be controlled at the boiler -- not with an in-house thermostat at all. If it's a mod/con you can get the thing to run in condensing mode (and hence very high efficiency) most, if not all of the time.

    If you need to boost the temperature in one specific space from time to time, I'd suggest a separate zone with panel radiators (or possibly baseboards) controlled by a local thermostat -- I'd probably use a simple Honeywell, but there are others. Don't try to manipulate the temperature of the slab.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Jean-David Beyer
  • Gta
    Gta Member Posts: 133
    It’s a 23 kw lion electric boiler.... I’m not sure how I can make it more efficient
  • HVACNUT
    HVACNUT Member Posts: 4,194
    A simple Tekmar 161 will be fine. Set it and forget it.
  • Gta
    Gta Member Posts: 133
    Guys another question... I have a Erie boiler boss SR301. My question is I have 3 zones : with 3 separate pumps and 3 separate t stats.

    The main house is priority. When it runs the other 2 will wait .

    But If the other 2 happen to call for heat at the same time they run together...?😮😡 that can’t be right? Especially as one is the garage set at 11c and the other is my bonus room set at 20c

    How can I set it to run only one pump at a time ?
    Thx
  • SuperTech
    SuperTech Member Posts: 1,687
    edited February 2020
    > @Gta said:
    > Guys another question... I have a Erie boiler boss SR301. My question is I have 3 zones : with 3 separate pumps and 3 separate t stats.
    >
    > The main house is priority. When it runs the other 2 will wait .
    >
    > But If the other 2 happen to call for heat at the same time they run together...?😮😡 that can’t be right? Especially as one is the garage set at 11c and the other is my bonus room set at 20c
    >
    > How can I set it to run only one pump at a time ?
    > Thx

    What's wrong with two zones calling at the same time? The boiler doesn't care what the thermostat is set for. Priority zone is normally used only if you have a domestic hot water zone. Typically a correctly sized and installed boiler should be able to operate if every heating zone is calling simultaneously.
  • Gta
    Gta Member Posts: 133
    Hmm good point , I only ask because I’m my mind it would be easier to heat 1 zone at a time .

    Anyway I’m using only 90-95 * water the house/ zones are getting to set temp easily. At this temp only 1-2 elements are coming on ... if I set it any higher all 4 go on then shut off repeat over and over .

    Anything wrong using such a low boiler setting? Thx
  • Jamie Hall
    Jamie Hall Member Posts: 17,049
    I would get your automatic controls set up properly and make sure that all the zones are circulating all the time with primary/secondary piping, mixed -- using the outdoor reset -- to the required temperature. Then the boiler should run just enough to maintain the required heat input to the floors -- whatever that is. A significant advantage of an electric boiler is that it can run at whatever temperatures are needed.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England