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Recently purchased a Honeywell CT87K

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To replace an older than dirt honeywell thermostat in my apartment. Know literally nothing about these things am hoping someone can offer some guidance.

As you can see in the pictures the circuit board?? Has an R wire W wire and a B wire?
The 87 has an R W and a Y. I have attached the B wire to the Y terminal. Is this correct? Or should i just tape up the B wire and leave it unattached. Thanks for anyone who can help

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,117
    edited October 2023
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    This will depend on what the thermostat is connected to. Most controls will use R and W on a thermostat to turn on an heating device and when R and W contacts break the heating device will stop heating. This is true for gas valves that turn on burners in furnaces and boilers, this is true for oil burners that are on furnaces and boilers. This is true for most zone valves. Power on and the motor opens the valve. Turn off the power and a spring will close the valve.

    There are some rare circumstances that require a power to open and power to close valve to operate a heating zone. This means that when R and W make contact the valve will open and allow heat to go thru a pipe or a duct. Once the room is warm and the thermostat is satisfied, R and W will open. At the same time R and B will close sending power to the valve motor to close the valve. If you have one of those controls, you may not be able to use the CT87K thermostat. I'm thinking that you have one of those controls by the moniker you selected @itswaytohot

    Can you take a picture of what control is on the other end of that thermostat wire (Maybe in the basement). It will definitely be in or near the heating system somewhere.


    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,117
    edited October 2023
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    I am not sure that this will work for you but you can try it.

    To fool the thermostat into thinking it is a SPDT thermostat like the one you need for WhiteRogers 3 wire zone valve or a Honeywell series 20 control try this

    1 set the dip switch on the thermostat Wall Base to E for electric heat.
    the Y terminal on the CT87K will now be W (from the old base)
    The R and RC jumper terminals will be R (from the old base)
    The W on the CT87K will now be the B (on the old base)

    If this does not work then you may need to use an isolation relay and a separate transformer

    Let me know tomorrow, I'm heading to bed now. Oops it is already tomorrow. Let me know later this morning. LOL

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • itswaytohot
    itswaytohot Member Posts: 6
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    Hi thanks for both of your replies. A little about myself I’m just a tenant in an apartment building and have no access to the boiler room. The reason why i went ahead an purchased and installed this unit was because the heat had been off in my building for the summer months. Then they suddenly they switched it back on (water baseboard heaters) and it was going full blast. The old thermostat which was as you can see in the picture was a mercury bulb type. And was completely unresponsive. Since it was a long weekend in my neck of the woods and the building manager doesn’t respond at the best of times. I researched online and thought that I had found something comparable in the 87. But i now think it has to do with the check valve. Since the heat is still going full blast. Just like with the old thermostat. Finally got a response from the manager late last night and shes sending their “hvac” guy out soon? Have been suffering for days with 80+ degrees of non stop heat and decided to take things into my own hands looks like that may have been a mistake. Thanks again for the replies and will update the final result once it gets fixed.
  • itswaytohot
    itswaytohot Member Posts: 6
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  • itswaytohot
    itswaytohot Member Posts: 6
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    Just a few numbers if this helps anyone.
  • Jamie Hall
    Jamie Hall Member Posts: 23,447
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    It is very unkkely that the old thermostat was not operating -- but it is very easy to check. With it off the wall, use an ohmmeter or multimeter and measure the resistance between R and W. With the thermostat held so that the mercury is towards the wire end of the bulb, the resistance should be very low or zero. If the thermostat is tilted so that the mercury goes the other way, the resistance should be very high or show open circuit.

    It the thermostat passes that, it's working just fine.

    HOWEVER. They are very sensitive to being mounted level. Even a few degrees off level will throw them off several degrees F.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Steamhead
    Steamhead Member Posts: 16,902
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    Look at the model number- it's T26A, which means it's a Series 20 control that "makes" one wire to turn the heat on, and another to turn it off. Also, it's branded "Heat-Timer" which is a company that makes specialized control systems for larger buildings. So it's anyone's guess what it is connected to, if it's connected at all. Whatever it is, is probably in the boiler room- do you have access?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • itswaytohot
    itswaytohot Member Posts: 6
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    You are correct Steamhead and thanks. Unfortunately no access to the boiler room. I live in a 60 year old apartment and getting any kind of service done takes weeks. Due to the fact that it’s blasting out nonstop heat 24/7 and my apartment is over 80 degrees i decided to take matters into my own hands… from my research the B wire appears to control the shut off valve?
    Actually broke down called Honeywell tech support. Was instructed by them to just tape off the B wire. But that did nothing for the nonstop hot water heat blasting into our baseboards. So put in a request a week ago now to get this thing fixed and now have no other option then to sit and wait and sweat it out. Will update with the final fix once it’s done. I want to thank everyone for their input and suggestions. Thanks.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,631
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    I agree with @Steamhead that is likely a T26 used on zone valves etc
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,117
    edited October 2023
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    Hi thanks for both of your replies. A little about myself I’m just a tenant in an apartment building and have no access to the boiler room. The reason why i went ahead an purchased and installed this unit was because the heat had been off in my building for the summer months. Then they suddenly they switched it back on (water baseboard heaters) and it was going full blast. The old thermostat which was as you can see in the picture was a mercury bulb type. And was completely unresponsive. Since it was a long weekend in my neck of the woods and the building manager doesn’t respond at the best of times. I researched online and thought that I had found something comparable in the 87. But i now think it has to do with the check valve. Since the heat is still going full blast. Just like with the old thermostat. Finally got a response from the manager late last night and shes sending their “hvac” guy out soon? Have been suffering for days with 80+ degrees of non stop heat and decided to take things into my own hands looks like that may have been a mistake. Thanks again for the replies and will update the final result once it gets fixed.

    You should already know about the NYC tenant thermostat... Open a window if it gets too hot. Place a blanket over the radiator(s). Then walk around the apartment (condo) naked.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • itswaytohot
    itswaytohot Member Posts: 6
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    Was a valve problem in the unit below us. Don’t think he even used the B wire now have a fancy T6 pro to replace.