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High thermal mass control strategies?

JL_2 Member Posts: 17
Does anyone have any ideas on controls foe high thermal mass? I came across a low mass atmospheric boiler with a high mass slab panel. It has been condensing most of its life partially due to the way it is piped and partially because of the application. I am going to add a primary loop with a four way motorized mixing valve with out door reset. Hopefully taking care of two issues, boiler perfection and adjusting supply temps to comfort zones with outdoor reset. In hoping the outdoor reset is going to help with the overshooting problem. Is there anything else I can do? I can't incorporate slab sensors but maybe there is some sort of retrofit slab sensor?


  • SWEI
    SWEI Member Posts: 7,356
    Outdoor reset

    is the primary strategy, so start with that.  Consider the outdoor temp sensor location carefully -- you can do a lot with that, especially with solar gain.  Are there indoor heat sources like a woodstove or fireplace insert?  Consider zoning the affected rooms separately, using a thermostat as a high limit control for them.
  • Zman
    Zman Member Posts: 7,328

    Take a look at the tekmar TN4(or TN2) controls.

    It sounds like you need a combination of outdoor and indoor feedback. The tekmar will learn from past indoor overshoot and anticipate to some degree.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • jch
    jch Member Posts: 29

    Makes a couple of thermostats that you can specify either low- or high-mass with a switch. For high-mass it uses pulse-width-modulation to vary the amount of heat applied to the floors from the desired temp. Take a look.
  • JL_2
    JL_2 Member Posts: 17
    Tn2 vs Tn4

    Yes. Looks like the tekmar indoor feedback with outdoor reset is the best thing to do.

    Do you know the difference between the tn2 and tn4? The only thing I can see is 2 wire vs 4 wire but I don't know what the extra two wires do?