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Control Strategy for radiant floor

Wayco Wayne
Wayco Wayne Member Posts: 615
where I have extruded plates upstairs and concrete embedded tubing downstairs. My highest temp need is going to be 120 F. My lowest 90 F. I am using a condensing boiler that has outdoor re-set capabilities. I was going to use a duo-mix 2 injection control, but then thought Why not use the boiler re-set for the 120 F loops and just use a zone valve and tek mar wall t/stat for the concrete. It would be simpler and perhaps less money. What do you guys think??? WW

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  • Dave H_2
    Dave H_2 Member Posts: 534
    Dual Temp system


    Use a manual mixing valve, not thermostatic, it will work proportinately off the boiler.

    As the temp of the boiler changes, so does the temp of the mixing valve.
    Dave H
  • chris smith
    chris smith Member Posts: 39
    quick question

    where are you getting your domestic hot water from any plans for an indirect in your future

    chris smith

    paradise porter maine
  • Embedded mix

    Use an indoor reset control if you can, what it can do for your comfort, efficiency and system operation is most definitely worth investigation. Mix for the 120 degree zones, then use a balancing valve off of the radiant circuit to redirect some of the return water from the slab back into the supply for the slab. You can get a decent, fairly consistent differential between the plate and the slab that way.

    And never use a zone valve where you could use a pump instead. Zone valves fail more often and give you no benefit; not even a cost benefit, usually, unless this is an open system. Circulating cast iron pumps are quite cheap and long lasting.
  • heatboy
    heatboy Member Posts: 1,468
    Dual temp radiant.


    The simplest solution would be to reset the suspended radiant via VSI or motorized mixing valve sized for all of the radaint, then add a manually set three way valve downstream for the lower temp slab. The suspended will, naturally, modulate and the three way will also due to the modulation on the suspended, albeit at a lower temperature. You will need a pump downstream of the manual three way to make it work. Stay away from using boiler reset for the floors. Not enough finite temperature control for the floor, especially wood floors. Someone will tell you that the differential can be tightened to keep water temperature swings lower, but that will lead to some pretty crazy boiler short cycling.

    Other than that, use a two temperature control. A Wirsbo 311 plus either a proMIX 101 or 201 will control two temps plus and indirect. You didn't mention what boiler/control all of this is tying into, so some control options will work better than others. If you let me know behind the Wall what equipment you are using, I give you some input, if you would like.


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  • Paul Pollets
    Paul Pollets Member Posts: 3,648
    That's how

    I do it...with thermometers to be able to check the outgoing temps to the manual mix

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  • Wayco Wayne
    Wayco Wayne Member Posts: 615
    Thank you all for your input.

    I am planning on using a Munchkin on the job, and am hoping to use their new controls with the multiple set points. Not sure how it works yet. Am going to a Dog and Pony show put on by the local rep today. Went to the first meeting of the Washington area RPA. Dave Yates was the speaker. One picture he showed us showed a system shere he used the return water from a higher temp loop to run a lower temp loop. Gawd I love stuff like that. I am wrestling with the idea of an indirect. Not sure yet.

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  • Jed_2
    Jed_2 Member Posts: 781
    Can you really

    run a Munchkin in condensing mode with an Indirect calorifier?

This discussion has been closed.