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Replacing a thermostat wiring questions

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danspawn85
danspawn85 Member Posts: 14
in A-C, Heat Pumps & Refrigeration

Hello all,
My central air is messing up, and I don't know if it's related to the wiring, or if the mercury switches are going bad. The heater will come on and run for a time, then shut of, however the fan continues to run, and run, and run, then the heater will kick on again. I have to manually turn it off most of the time.

As you can see from the picture the brown wire that goes to E has been severed and the W2 wire goes to E and is then jumped to W2.


I rent so I'm not sure if the Emergency heat doesn't actually work, and that's why it's been severed.
If the thermostat doesn't have a place for C is it really needed?

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
    edited January 2021
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    Your system is a heat pump. The G with the green wire is the fan relay. Your thermostat has a C terminal and yes it needs to be connected so the indicator lights will have a return path to the control transformer. If you are renting is the landlord responsible for HVAC repairs?

    The W2 and the E are jumpered together because you have only one bank or electric backup heat. E is used when you switch from Normal to Emergency heat. W2 is used when you switch to Normal heat and the compressor is unable to keep up as the outdoor temperature goes below the break-even point. That is when the second stage of heat (usually electric resistance heaters) kicks in. That is connected to the second mercury bulb that tips.

    By the way that the brown wire is wrapped around the rest of the wires, that is an indication that it is not connected to anything on the other end of the wire. It is a way we indicate that it is an unused wire.



    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • danspawn85
    danspawn85 Member Posts: 14
    edited January 2021
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    Yes, he is, but due to Covid-19 I won't be bothering him with it.
    If I need to get a replacement that has the C hook up, then that's what I'll do, but the replacement I bought doesn't have that particular hook-up.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    What thermostat did you select?
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • danspawn85
    danspawn85 Member Posts: 14
    edited January 2021
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    Honeywell Home digital for gas/oil or electric/ heat pump. non programmable
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    Not enough wire terminals for your system. There is no way to connect the electric heat relay on that model.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • danspawn85
    danspawn85 Member Posts: 14
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    I don't suppose you could send me a link to an affordable one either at a Walmart or Lowes. I'm not really sure what to get, and you can't exactly remove them from the package to see.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    You need to have a thermostat that has 2 stage heat for a heat pump system. Here is one that will work for you

    https://www.supplyhouse.com/Honeywell-TH3210D1004-PRO-Non-Programmable-Digital-Thermostat-2H-1C-Horizontal-Mount-5471000-p?gclid=Cj0KCQiA0fr_BRDaARIsAABw4Ev0jLgCKumzWjJCCGutIxQMxatTAIvM1__Qb26KuzkV-2Pq4FAgTSsaAioSEALw_wcB

    After you replace the thermostat and the fan does not stop running, What will you check next?
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • danspawn85
    danspawn85 Member Posts: 14
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    Why would the fan continue to run then?
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    is it possible that the green wire is shorted somewhere? You can check by removing the green wire from the G terminal on the thermostat. Then power the system up and see if the fan operates.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • danspawn85
    danspawn85 Member Posts: 14
    edited January 2021
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    That's a no, I removed said wire, turn the heat on, it turned on. I then turned it off and put the fan on "on" it did nothing.
  • danspawn85
    danspawn85 Member Posts: 14
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    It doesn't do it when I run the A/C at all, just the heater, I don't know if that helps.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    There is an issue with the air handler. You will need to get a pro that understands the wiring of heat pump control wiring
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • danspawn85
    danspawn85 Member Posts: 14
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    After watching several videos, most don't cover the problem. It's not constantly on, I can shut it of by sliding the temperature slider up and down.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
    edited January 2021
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    so let me understand your explanation.

    when you set the thermostat to Heat. The fan operates constantly. This means when the outdoor unit operates the fan is blowing warm air, then when the outdoor unit goes off because the room temperature reaches the set point, the fan continues to operate blowing cold air.

    But in a later post, you said you can control the fan by turning the setpoint to a lower temperature. This means when the setpoint is reached the fan goes off. This is the way it is supposed to operate.

    Both of these statements contradict each other. Can you please explain more clearly what you believe to be the problem?
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
    edited January 2021
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    danspawn85 said:

    That's a no, I removed said wire, turn the heat on, it turned on. I then turned it off and put the fan on "on" it did nothing.

    Please explain "IT"

    If I read IT to be THE FAN then your statement reads as follows:
    danspawn85 said:

    That's a no, I removed said wire, turn the heat on, THE FAN turned on. I then turned THE FAN off and put the fan on "on" THE FAN did nothing.

    Sorry, this does not make sense.




    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    How long have you lived in this rental unit? Is this your first winter?
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • danspawn85
    danspawn85 Member Posts: 14
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    The furnace turns on, runs for a time. Then the heat turns off, the fan continues to run. Sometimes the fan can run for 10 minutes and shut off by itself, other times it will continue to run till I get up, slide the temperature slide up and then down. Shutting both off. It's fickle. It won't turn the fan off if I just move it to a lower temp, I have to engage the heater, and slide it back to a lower temp or turn the whole system off.
  • danspawn85
    danspawn85 Member Posts: 14
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    danspawn85 said:

    That's a no, I removed said wire, turn the heat on, the heater turned on. I then turned the heat off and put the fan on "on" the fan did nothing.

  • danspawn85
    danspawn85 Member Posts: 14
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    No it's just the first winter in which it has done this.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    When you say Furnace, are you speaking of a Gas-Fired furnace? Or is the furnace you refer to an electric furnace?
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • danspawn85
    danspawn85 Member Posts: 14
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    It's an electric trailer furnace/ heater whatever you call it.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
    edited January 2021
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    danspawn85 said:

    That's a no, I removed said wire, turn the heat on, the heater turned on. I then turned the heat off and put the fan on "on" the fan did nothing.

    Ok, your test did what I would expect Since the G terminal on the thermostat is the one that operates the fan, then the fan should not operate at all when you set the fan switch to FAN ON while the G wire is disconnected. When set to automatic the fan on a Gas Furnace would operate after the furnace heated up the plenum chamber where the temperature limit control is located.

    Do you have a control that looks like this?



    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    Electric OK that makes sense now. Does the outdoor unit run for heat? or does it only run for AC
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • danspawn85
    danspawn85 Member Posts: 14
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    this is the underneath, don't know if it's under thereThe outside unit does both.
  • danspawn85
    danspawn85 Member Posts: 14
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    If any contacts were fused together, it wouldn't shut off at all would it? 
    I'd have to shut it off at the breaker box.

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    I do not believe your thermostat is the problem. The cold temperatures cause the outdoor unit to operate constantly. it will never cycle off when the outdoor temperature is below the "Break Even" point of the system (usually near 30°F). As the outdoor temperature drops lower to say 25°F the heat pump compressor operates but can not supply enough heat. In this case, the other mercury bulb tips and the electric resistance heat supplements the heat pump in order the provide enough heat for your home.

    Once the electric resistance heat is no longer needed the mercury bulb will tip the other way and the electric resistance heat will stop heating, but the heat pump will continue to heat the home. The auxiliary electric strip heat may come back on then shut off, again and again, the whole time, the heat pump compressor will continue to operate along with the indoor blower fan.

    once the electric strip heat activates, There is a control inside that makes sure the fan stays on until the electric strip heat cools down. This video is helpful in seeing the cycle of the heat pump with auxiliary strip heat https://www.youtube.com/watch?v=Qa5Ou6NUjH0

    Electrical controls on a heat pump can be difficult for professionals to troubleshoot. You will need an electric multimeter to determine where your problem is. One of the relays inside the control panel may be defective or the system may just be operating the way it should. If you are not familiar with heat pump control wiring, you should let a professional handle the problem.

    That is my recommendation

    Yours Truly
    Mr.Ed

    Good night

    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics

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