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Selecting a Heating and Cooling Control System

Building a house and we installed the following...
  • Radiant PEX Heat with aluminum heat transfer plates...
  • 1000 square feet 1st floor - zone 1 - 6 loops
  • 600 square feet 2nd floor - zone 2 - 5 loops
  • 3 pumps, one pump for each zone, and a primary loop
  • target water temp 120 degrees F
  • Hardwood Maple floor

  • Mitsubishi Mini-Split...
  • 1st floor - zone 1 - central located ceiling mount caste
  • 2nd floor - zone 2 - 3 wall mounted units, one for each bedroom
Questions, is there a way to centrally control all of this?
If so can we control the loops (manifold actuator) and not just the zone pumps. Each bedroom on the 2nd floor has a dedicated loop. In this way each bedroom would have it's own thermostat, and individual control of the rooms temperature.
Ideally this same thermostat controls both the radiant heat and min-split.
The system would also monitor the floor temp and prevent overheating of the hardwood maple flooring.

Looking for ideas and suggestions on a control system that can do both the mini-split and radiant heat, the zone pumps, and loop (manifold actuators), and underfloor temp monitoring.

Thank you


  • Jamie Hall
    Jamie Hall Member Posts: 18,951
    Your radiant heated floors should be controlled with outdoor reset and should always be on -- no setbacks. You may need to have separate mixing valves for the various radiant zones, since it appears you want to have the various zones at different temperatures.

    Don't even try to vary the space temperatures using the radiant floors. The lag is way too long. Once you get the mixing valves and outdoor reset curves set, leave it be. Use the floors to maintain a desired low base temperature

    You should be able to control the mini-splits with regular thermostats, and raise the temperature in individual zones that way.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 9,765
    Anything can be done, it is just how complicated you want things to be.

    Looking ahead to 10 years and some component dies and the entire system is not working, who will figure it out?

    You may be installing all this yourself and know all the functions.

    I did this and was certain I had a handle on everything.
    25 years later I have to think a lot about how everything should work.
    Then in 10 more years I might not be able to travel to, or even find, the basement.

    A little reading on this site will reveal how little some techs know about controls.
    Their answer is to tear it all out and put in a fully ducted forced air system.
  • RodHot
    RodHot Member Posts: 22

    Thank you for the feedback!

    Jamie Hall - the point of using an ODR and mixing valves to keep the radiant heat at a steady/consistent temperature makes sense. This would be your "base" room temperature. I assume though one could adjust the flow through the manifold to have some areas (rooms) consistently cooler (bedroom) or warmer (bathroom) by a few degrees? And the lag is also understandable.

    JUGHNE - Keeping it simple is prefeed. I think back on things done 10 or 15 years ago and not sure I could revisit and figure out what I did then now. So I can't image what another 20 or so years will be like.

    Of biggest interest in the control setup is floor temperature monitors (thermostat sensor), are they necessary to protect wood floors from damage due to over heating? I read in many places, including here, that 85 degrees is the max temperature for the wood floors. If my target water temp is going to be 120 degrees will I run the risk of overheating the wood floors over time?

    For example would a device like the Watts Radiant 519 with floor sensor 079 be sufficient? One for each floor (zone).

  • Jamie Hall
    Jamie Hall Member Posts: 18,951
    Yes, with the loop setup you have you could easily modulate the flow to the various loops to run your floors at different temperatures if you wanted to. Not a problem.

    Having a floor sensor isn't a bad idea, but it would be there only to shut things off if for some reason that system started overheating the floor -- not really a control, then, but a safety device. You may find that your target water temperature is less than 120 -- in fact that wouldn't surprise me at all. And also yes, there is a risk of overheating wood -- or vinyl tile! -- floors. The device you mention will do nicely.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 9,765
    I have a sun room with infloor heating. Ceramic tile over concrete.
    That water temp is mixed down to 95-105.
    The boiler max is 120, so if mixer fails tubing is still safe, just hot floor.

    I accidently lucked out by placing the tstat such that the winter sun hits it and shuts down the floor heat during a good heat gain day.

    We did embed a piece of 1" soft copper with a sweeping bend coming up out of the floor into the plate of a wall. The buried end is sealed shut and the open end in the wall has a blank electrical plate for access.
    This potentially would be for a infloor sensor, presently has only a thermometer probe inserted.

    Saw this done in hog farrowing barns with electric pads in place for piglets.
    Sensor tube had a sealed end and then filled with oil. A copper cap tube tstat bulb was inserted down into the oil to get a stable reading of the slab.
  • RodHot
    RodHot Member Posts: 22
    Again, thanks for your input.

    How many floor sensors should be installed? I have 5 loops for my second floor zone. Should 5 floor sensors be installed one for each loop, or install one floor sensor for the entire zone (5 loops)? If one I assume attempt to install it in the hottest loop?
  • neilc
    neilc Member Posts: 1,805
    5 loops, but how many zone(s) ?
    one sensor per zone should do you,
    unless you have some crazy local solar gain, or other distinct situations
    you would balance the loops per zone at the manifold
    known to beat dead horses
  • RodHot
    RodHot Member Posts: 22
    edited March 7

    Thanks, we have two zones. Zone 101 has 6 loops. Zone 201 has 5 loops. One zone for each floor.