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Stat with 12k sensor

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Jeff Perry_3
Jeff Perry_3 Member Posts: 99
in THE MAIN WALL
Anyone know a 24volt thermostat available that uses a 12k ohm floor sensor rather than the more standard 10k ?

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  • mattmia2
    mattmia2 Member Posts: 9,639
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    It is a curve that varies by specific thermistor. Simply knowing the 25 c resistance doesn't tell you enough about what its curve is, there is another parameter or 2 that indirectly describes the slope of the curve.
  • Jeff Perry_3
    Jeff Perry_3 Member Posts: 99
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    I should have explained better..... I have an existing stat that uses a 12k ohm floor sensor. The idiots that installed it didn't make it accessible for me to be able to change it. I need to change the thermostat so if I want to continue to use the existing floor sensor I need to find a stat that uses 12k instead of 10k.
  • pecmsg
    pecmsg Member Posts: 4,845
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    Mount a new sensor on the return line.
    mattmia2
  • Jeff Perry_3
    Jeff Perry_3 Member Posts: 99
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    And what, we're going to assume the return is going to be the temperature of the floor? I don't think I want to go there. I know the Europeans use 12k sensors so I really just want to find a Stat available here that uses it too.
    Thank you though.
  • hot_rod
    hot_rod Member Posts: 22,139
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    Shop some offshore suppliers, Amazon UK for example
    Salus is a common brand in Europe
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • pecmsg
    pecmsg Member Posts: 4,845
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    Jeff Perry_3 said:

    And what, we're going to assume the return is going to be the temperature of the floor? I don't think I want to go there. I know the Europeans use 12k sensors so I really just want to find a Stat available here that uses it too.
    Thank you though.

    Actually the return should be a few degrees above the return.

  • pecmsg
    pecmsg Member Posts: 4,845
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    Sorry
    A few degrees above the floor temp.
  • ratio
    ratio Member Posts: 3,626
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    It may be possible to use resistors to tweak the 12K sensor into something close enough to 10K to use. It probably wouldn't be terribly accurate across it's entire range, but it should be good enough at the target temp & some few degrees on either side.
  • mattmia2
    mattmia2 Member Posts: 9,639
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    ratio said:

    It may be possible to use resistors to tweak the 12K sensor into something close enough to 10K to use. It probably wouldn't be terribly accurate across it's entire range, but it should be good enough at the target temp & some few degrees on either side.

    Maybe if you calibrate it for a specific temp. It wouldn't work well if you changed the setpoint by more than a couple degrees from the point you calibrated it at.
  • ratio
    ratio Member Posts: 3,626
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    mattmia2 said:

    Maybe if you calibrate it for a specific temp. It wouldn't work well if you changed the setpoint by more than a couple degrees from the point you calibrated it at.

    Right. Not perfect by any means, but if you dial it in at the temp you plan on running at, you should be fine. At worst, you'd have to think of the settings as 'warmer' and 'cooler', rather than a whatever° temp setpoint.

    The first 12K thermistor table I found (PDF here) shows around ±1 KΩ difference for 2° C around 25° C (77° F), which is a fairly close match for a 10K type 2 sensor, with types 3 and 4 being progressively poorer matches.

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