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12 Volt, 6 Wire, Hydronic Radiant Floor Heat Thermostat by Radiant Technology

sunsetace
sunsetace Member Posts: 3
in Radiant Heating
I need to replace three of these 12 Volt, 6 Wire thermostats and cannot find them anywhere or in any brand, everything is 24 or 120 volt. The system was installed around 12 years ago and now the thermostats only function in an on/off mode and I can't control the temperature.

Any help or suggestions would be greatly appreciated - short of replacing the entire system :)

Comments

  • Zman
    Zman Member Posts: 7,611
    What is the other end of the tstat wire connected too? 12 volt is pretty unusual as is 6 wires. Is there a floor sensor?
    You are probably going to need to convert to 24 volt.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    sunsetace
  • sunsetace
    sunsetace Member Posts: 3
    I am waiting to get an answer on what it is connected to, was not installed by me, not sure if there is a floor sensor, but I don't think there is - will post the answer as soon as I get it.

    Here is a photo of the wiring.

    How would I go about "converting" to 24 V?



  • Zman
    Zman Member Posts: 7,611
    There is a controller of some sort in your boiler room. It likely has at least 4 of those wires connected. Someone who has seen that t-stat may chime in, my guess is that 2 wires go to a floor sensor and 4 go to boiler room
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    sunsetace
  • sunsetace
    sunsetace Member Posts: 3
    ...and so the plot thickens, or loosens.

    Suddenly, it is no longer 12 volt, it is 24 volt.

    You are correct, 4 wires to controller in boiler room, 2 wires to the floor sensor.

    Most of the tstats I see are only 2 wire, can you recommend a non programmable, 24 v, 6 wire, radiant hydronic tstat?

    Thank you so much for your help, I have been trying to resolve this for a really long time!

  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    Have you looked at Tekmar thermostats. You may not need all 4 wires to the boiler, and they have the 2 terminals for the floor sensor.

    There was an error rendering this rich post.

  • Zman
    Zman Member Posts: 7,611
    The tekmar is probably the way to go. You may have a complication with the floor sensor. I may not be compatible with the tekmar. Do you know where it is? Can you remove it.
    The other option is just to use 2 or 3 wires, use any thermostat and forget about the floor sensor.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • kennyD
    kennyD Member Posts: 3
    I too have this tstat and want to replace. Does anyone have model number and install instructions? What are each wire connected too?
  • hot_rod
    hot_rod Member Posts: 23,385
    That was a very common radiant stat back in the day, most all the radiant manufacturers used it. I think it was made by ESBE in Sweden.

    As I recall it had 24V R&C on two terminals, two switched, and two for a remote or floor sensor. Might find them on e-bay from time to time.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • kennyD
    kennyD Member Posts: 3
    thanks hot_rod
    i am looking to replace with tekmar 518
    any idea which terminals are 24v R&C, which are switched and which are floor sensor
    Thanks for your help
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,214
    edited May 2022
    I remember those thermostats, but not the manufacturer. The removal screw was behind the dial.

    Edit: The picture shows the model number: MTC. Here is a link to more information.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • kennyD
    kennyD Member Posts: 3
    Thanks Alan
  • TAG
    TAG Member Posts: 757
    I had them years ago ... my replacement said OJ Microline with the OJ being the manufacture out of Denmark. Hot Rod is usually correct -- so maybe they are a reseller and actually made in Sweden.

    See them still available ? Do you only have one?

    The OP back in 2019 had three go and that seems odd .... wonder if it was something else.

    My memory is they were simple on off power switch. Two wires for power ... two for control and two to the floor sensor. The OP's picture is odd because the sensor had black wires ?

    I like the Honeywell setup from supply house -- it's both a room and floor in a nice small package for a sub $100 price. The key is knowing about the floor sensor -- compatibility
  • hot_rod
    hot_rod Member Posts: 23,385
    Alan has the correct manufacturer shown 


    They come in line voltage versions also, Watts Radiant used them for electric radiant mats sold as as SunTouch or Heatweave
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,214
    Really? I’m correct? Is it time to change my tag line?
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • hot_rod
    hot_rod Member Posts: 23,385
    Alan (California Radiant) Forbes said:
    Really? I’m correct? Is it time to change my tag line?
    Often right, never in denial😉
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Tinman
    Tinman Member Posts: 2,808
    The tekmar 519 is the same as the 518 but comes with the sensor wire. 
    Steve Minnich
  • Karl Reynolds
    Karl Reynolds Member Posts: 67
    Check with Danfoss. They purchased a lot of the ESBE / RTI product line. Their MTC-39994-UF thermostat is a dead ringer of the photo that you posted. Or the MTC-39914-UF with the floor sensor.

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