Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

outdoor reset for radiant floor heat

dave63 Member Posts: 3
I am working on a Firehouse/social hall with radiant floor heat. The system has a simple Tstat that controls the circulator. The problem is the room temp overshoots in the afternoon and runs continuous in the morning. I think I want to add a outdoor sensor and slab sensor and control it with an outdoor reset.

Will a Honeywell outdoor reset boiler control work for this? What control should I use?


  • SWEI
    SWEI Member Posts: 7,356
    What kind of boiler?

    If it's a conventional boiler, I'd suggest adding a motorized mixing valve controlled by ODR.  A Taco iSeires-R is usually the least expensive way to accomplish this.
  • dave63
    dave63 Member Posts: 3

    The system has a conventional boiler with 2 indirect fired water heaters. The system circulates 120 deg. water through the floor from the indirect water heaters. I can adjust the floor loop temp by changing  the thermostat setting on the indirect water heaters.

    What I am looking to do is shut down the floor loop circulator before the room temp climbs and start the loop circulator early when the outside temp drops.  
  • Zman
    Zman Member Posts: 7,330

    It sounds like an unusual setup. Are either the boiler or the radiant loops tied into the domestic water or are they isolated?

    It sounds like you need to vary the temp in the tanks based on the temperature outside (outdoor reset control).This will help you apply the correct amount of energy to the floor based on your actual heat loss a any particular time. There are quite a few ways of doing this. If you post a picture or drawing of your system we should be able to point you in the right direction.

    Depending on how much solar gain you are experiencing, you may want to consider Tekmar TN4 controls. The TN4 system has the ability to anticipate an overshoot. They work pretty well. With a high mass slab it is very hard to completely eliminate overshoot.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • dave63
    dave63 Member Posts: 3
    edited June 2013

    I looked into the Taco mixing valve. I was hoping to gain better control without doing any plumbing but I believe this will give me the best control. And I don't have to do all the zones right away. This setup is Odd, the only one that I have seen this way and it does not work well.

    It looks like I could do away with the indirect water heaters after I put mixing valves on all of the zones.

    The boiler has a domestic HW jacket. The Radiant loop has its own pressure reducing supply and expansion tank. I also have a problem with migrating heat the tank temp overshoots from time to time. I was planning to install a solenoid valve to prevent this but I like the idea of eliminating the water heaters.  

  • Rich_49
    Rich_49 Member Posts: 2,692
    edited June 2013
    Operators of Hall

    using setback thermostats on this area ?
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • Gordy
    Gordy Member Posts: 9,514

    is on to something assume setback is being used to react as it is. This sounds plausable with a hall type of building.
  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    I would add

    that if you already have the indirects, keeping them is fine, they are good buffer tanks. mix off of them if you like.

    I would hope this is a tank in tank style indirect as well... certainly not that you are pumping potable water through your radiant?
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
This discussion has been closed.