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Honeywell Mechanical Thermostat Calibration

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watercress
watercress Member Posts: 31
edited October 2023 in Gas Heating
I have several of these Honeywell Mechanical Thermostats, they look like this:
https://www.honeywellstore.com/store/products/the-round-non-progammable-thermostat-ct87k1004.htm

One of them does not engage (you can hear it click) at the right temperature. It is about 5 degrees off. Since I have several around the house, I went ahead and popped the face off one, and stuck it on the other. That narrows it down to being the face itself, not the mount or if its level (not sure if these really require to be level since it is not mercury).

So wondering is there a way to to "calibrate" these things so they engage at proper temp? By proper I mean the temperature thats on the bottom dial... when you turn the top dial beyond what the bottom dial reads, you should hear the click. On this one unit, it does not engage until turning the top dial 5 degrees past the bottom dial.

Or is it just a junk unit?

Comments

  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    If there was a meme of someone throwing something into a trash can or a bonfire, this would be a good place for it. Wait...think I found one.
    https://youtu.be/FhOy6YAQmpI?si=dIGJgEXXKbSxGh_Y

    There was an error rendering this rich post.

    watercress
  • watercress
    watercress Member Posts: 31
    edited October 2023
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    Suggestion on what I should replace it with? Easy thing to do would go return this one and hope the next one actually works properly since I won't have to unscrew the plate.

    Edit: just had another one stop working... so I only got 1 out of 3 that actually work properly. Probably need to choose a different model if anyone has a suggestion.
  • JUGHNE
    JUGHNE Member Posts: 11,077
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    If the thermometer is off you might be able to tweak it. If on the back of the dial there is a screw slot.

    Otherwise.......
  • ratio
    ratio Member Posts: 3,654
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    They're easily calibrated, check out the last page of the attached manual. While the special tool might not be as readily available as it was in the past, I'm sure a substitute may be found. An original tool is currently available at https://www.ebay.com/itm/325452332265, but that's a little high, even for a stat that will survive the EM pulse that knocks out civilization.

    PS: this stat can not be used to spy on you, like others with video and audio monitoring can (even if the government promises they don't!)

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,634
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    Are these new stats your are installing or are they stats that previously worked ok??
  • watercress
    watercress Member Posts: 31
    edited October 2023
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    @EBEBRATT-Ed They worked okay when I first installed them about 2 months ago.
    @ratio The manual seems to be for mercury switch style, the one I have are mechanical type.

    The stat itself pops off the wall fairly easy. You can pop the face off the stat itself although somewhat more difficult, possibly to change the battery? Here is what it all looks like:




  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    ratio said:

    They're easily calibrated, check out the last page of the attached manual. While the special tool might not be as readily available as it was in the past, I'm sure a substitute may be found. An original tool is currently available at https://www.ebay.com/itm/325452332265, but that's a little high, even for a stat that will survive the EM pulse that knocks out civilization.

    PS: this stat can not be used to spy on you, like others with video and audio monitoring can (even if the government promises they don't!)

    That’s the old one. OP has the new, horrible one.

    There was an error rendering this rich post.

  • Intplm.
    Intplm. Member Posts: 2,011
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    Some of the newer t-stats have a selector switch specific to the type of system it's being installed on.
    @watercress , have you checked for that?
  • watercress
    watercress Member Posts: 31
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    @Intplm. - Yes there indeed is some switches for what type of system on the back of the stat face. For these it is the stock setting for my application. Could be by having it set that way that the thermostat isn't even utilizing the yellow socket.
  • mattmia2
    mattmia2 Member Posts: 9,753
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    what emitters is the hot water heating? Y is for fan. The blue wire may go to common at the boiler or not be connected, you have to find the other end of it if you want to know.
  • watercress
    watercress Member Posts: 31
    edited October 2023
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    all the wires from the wall go to the zones, and then one branches off to the control board:
    image
    its the brown with a blue & green coming out that splice into two black wires and what appears to go to control board.

    All the heat is simple baseboard style copper closed loop hydronic.