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Best Thermostat for Radiant Slab Floors

BigRob Member Posts: 322
Happy Thanksgiving!

I've been pretty unsatisfied with my Nest E and the new EcoBee Premium controlling my hydronic slab. Lot's of over heating on sunny days. The Nest radiant feature doesn't seem to do much and the Ecobee may not be much better, even with the remote sensors.

Is there a solid, internet connected, radiant floor focused thermostat out there?

I was not smart enough to add a slab sensor during my last remodel. Nest and Ecobee should offer a remote slab sensor and the logic to interpret it!


  • hot_rod
    hot_rod Member Posts: 19,869
    You are correct that being able to sense or know the actual slab surface temperature can add more controllability. Slabs can be unruly as they are high mass and don’t respond quickly. South facing slabs with lots of solar gain can be a bear to control

    Ecobee had some weather responsive features where it monitored incoming weather/ temperature in an attempt to anticipate and begin the ramp up or down. I don’t know how successfully that function was?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • BigRob
    BigRob Member Posts: 322
    edited November 2022
    Their tech support just said to make sure the Ecobee is in "boiler" mode as there is some residual heating compensation in that mode. I'll let it learn and feedback in a month. I like the ecobee premium a lot more than the Nest E, anyway.

    I mentioned to Ecobee support to make a "floor" mode for their existing sensors or create a new housing that could be placed on a floor. Seems like a good way to address a decent high-end market. I would pay ~$100 for a floor sensor. I also tweeted them. : ) Anybody know a product person at Ecobee?
  • BigRob
    BigRob Member Posts: 322
    I will put a remote on the floor and play around and see how the averaging between all three of my sensors works out. The main display sensor has some compensation adjustment, so maybe I can get it to react correctly and have an accurate temp display.
  • nibs
    nibs Member Posts: 499
    We too have no slab sensor, but after much study and information given here, decided to use a Honeywell round mercury switch thermostat, with the advice to set it and forget it, we have been using it for about 5 years now and are completely satisfied. Our home has huge thermal mass so is a little unusual in that.
    In the fall we gradually raise the setting about 1/2 a degree at a time, (reverse in the spring. In summer we turn off the boiler, and in winter we leave it set at around 72F. Very rarely we get a temperature overrun and simply open a window or two to control it. We were a little concerned because as we opened the package we saw that we had a Nest box, but opened the box to find a new unused Honeywell with the plastic tabs still in place. I think perhaps the vendor was pranking us we had a chuckle.
  • Tinman
    Tinman Member Posts: 2,806
    tekmar 519 comes with the slab sensor. I’ve used them and like them. 
    Steve Minnich
  • BigRob
    BigRob Member Posts: 322
    Thanks for the Tekmar suggestion. The 561 looks good and is wifi, plus has floor and outdoor sensors, and of course the logic to address common radiant floor use cases. I may see if I can finagle a floor sensor somehow.