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outdoor reset

Smitdy Member Posts: 15
I got a question for other contractors regarding outdoor reset controls. My question is -The part that mounts on the outside of the structure, are they Universal/ interchangeable? My assumption is it's simply a resistor and that they are. I ordered one for a customer the other day that the previous contractor had not installed and the supply house gave me one for a different boiler model & manufacturer but said it will work for this one as well... and it did. If this is the case for all of them I will only have to stock one or two on my truck. -Chris, DBA: A-Plumbing&Heating


  • Big Ed_4
    Big Ed_4 Member Posts: 1,649
    It's just a resistor , If the sensor rating is the same for what it is called for on the ODR control it will work .. The sensor belongs on the NorthWest side of the building , not above a heat source like a window ...
    I have enough experience to know , that I dont know it all
  • Smitdy
    Smitdy Member Posts: 15
    @Big Ed, yeah I always follow the manufacturer's recommendations and mount the control where they say. I downloaded a compass app to my phone to find locations.
  • Jamie Hall
    Jamie Hall Member Posts: 15,415
    Well, a fancy resistor. Technically a thermistor -- that is, a resistor the resistance of which is proportional to the temperature. Any thermistor with the same relationship of temperature to resistance should work.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • The Steam Whisperer
    The Steam Whisperer Member Posts: 629
    IIRC there are typically two different types, a 12K (12,000ohm @ 72F) and a 20 K ( 20,000 ohm @ 72F) Just make sure to get the right matching setting.
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • PC7060
    PC7060 Member Posts: 274
    Also important to know that many sensors are non-linear so the replacements needs to match the profile in the Boiler manuals
  • Smitdy
    Smitdy Member Posts: 15
    @ steam whisperer I messaged the rep from Emerson Swan he told me all of their boilers (HTP) use 10k sensor.
  • Eric_32
    Eric_32 Member Posts: 267
    They aren't really that prone to failure to stock them in the truck. I think in 20 years I've had one or two give false readings that had to be changed.
  • ratio
    ratio Member Posts: 2,732
    There's actually a number of common thermistors and a whole passel of uncommon ones. You gotta pay attention to the details. There's at least two common 10K thermistors & one or two more uncommon ones. If you use them right around 25° C (77° F), any one of them will work—that's the 10K part. The further you go from 25° C, however, the further apart the different thermistors will measure, so it's not good to switch the thermistor type for an outdoor sensor.
  • Smitdy
    Smitdy Member Posts: 15
    edited February 21
    @Eric_32 the issue isn't that they are prone to failure is that another contractor has not installed it. Most recently I had to install one because the garage door installer had removed it not knowing what it is and thrown it away. He said it was in his way... of course he was a moron.
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