Questions tagged [thermostat]

Mechanical or electrical device used to control a heating, ventilation, and air conditioning (HVAC) system, or other temperature reliant system.

215 questions with no upvoted or accepted answers
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418 views

How can I tell if C wire is active and connected to Thermostats?

We are trying to install a smart thermostat (Ecobee 3) so we are in need of a C wire from our boiler. We see a green wire in the wall, but it's not connected to our thermostat currently since it ...
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310 views

Why won't a NEST that shares control of a furnace with a conventional thermostat turn on the heat?

I have three floors in my home. The bottom floor has its own gas furnace and the 2nd and 3rd floors share another gas furnace. Everything was working great until I added a NEST to the first and ...
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119 views

Why doesn't my A/C get power when using the alternate C-wire thermostat hook-up method?

I changed my old Honeywell thermostat for a new Honeywell WiFi thermostat. I installed it just as the directions stated. I used the alternate C-wire method as the old unit did not have one. ...
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1answer
899 views

Fan works for heating, but not for AC, where to start?

Our new place has a working AC (meaning that the physical box outside spins and can produce cold air) and a working fan (meaning that the fan spins and is able to put air out to the vents in the house)...
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1answer
560 views

Temperature in Condo hotter than thermostat setting- Gas Furnace

I recently bought my first place (a condo) and I have a gas furnace. The thermostat is set for 72 and most of the time it seems to be following this alright but periodically even though the thermostat ...
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2answers
2k views

Why might a thermostat refuse to switch from Heat mode to Cool mode?

I have this Honeywell RTHL2410C programmable thermostat and typical Florida electric AC system. Starting this Spring, it has started behaving strangely when switching from Heat to Cool mode. The ...
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1answer
753 views

How can I consolidate different heating/cooling systems into a single system?

I have 3 different types of heating/cooling systems that I inherited. Hot water heat. This heats the whole house/garage via 3 zones. Zone 1: Kitchen/Livingroom Zone 2: Bedrooms/Bath Zone 3: Garage ...
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1answer
2k views

How to connect Nest in Europe

I found a question regarding the Nest thermostat here. But that is only a question "Will it work?". Thanks to that I know it WILL, the problem is...HOW. I know the wire naming conventions are ...
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What is likely the problem with this HVAC system?

After running either just the central HVAC fan, or the central HVAC AC for just a few minutes, the Bryant thermostat (Model TSTATBBPB101, C Wire attached) screen momentarily shows "PF", and then goes ...
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18 views

Condo fan coil thermostat fan never turns off, cooling is humid

My thermostat in my condo is a honeywell thermostat and it the only options it has are System and Fan. Fan is set to auto (other option is Lo Med Hi) and the System is set to Cool (or Auto or Off). ...
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11 views

Ecobee installation with two Rh wires, occupied G wire and HRV

I just moved to North America from Europe (hence why furnaces, HRV systems etc are totally alien to me) and I'm having trouble understanding how to wire up an ecobee3 lite to replace my Honeywell ...
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1answer
48 views

Need a common wire

So, I recently moved. In my old place, I used my Nest without a common wire and never had an issue. However, in my new place, my Nest thermostat was working fine for about 20 days and started losing ...
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64 views

Did the handyman screw up or is there something wrong with my AC unit?

My landlord recently hired someone to install a common wire from my Goodman AC unit on the roof down to where the thermostat is. The current thermostat works fine, but is non programmable and battery ...
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33 views

Try to rewire Nest and Furnace but Y is not used on Furnace

I installed a Nest at home and it worked OK. Recently, I noticed there was a power issue. Google and others suggested adding a power supply by using the existing G wire because there are only 4 wires. ...
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40 views

Thermostat wire does not go to Furnace

My thermostat wires go to a control panel heat pump system which go to the furnance , i need to wire a c wire but not sure how to go about this with the york control panel
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16 views

Lennox Furnace Blower not working on AC In On or Auto

Please Help! I have a Lennox Furnace Model G60uhv(X) after years of working fine I switched the thermostat to AC and it failed to start the cooling cycle. I suspect some sort of problem with the ...
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18 views

Only blows hot air on both modes

I just installed a new Honeywell WiFi thermostat and my heat pump only blows hot air on heat and cool mode.
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13 views

Heat not kicking on

I live in an apartment with radiator baseboard heating and an old Honeywell round dial thermostat (no external switch). Heat has been working fine all winter. Weather has warmed up past few days- it'...
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25 views

Installed Honeywell R8285A 1048 control center combined with a Honeywell PRO 8000 thermostat

to operate an inline duct fan on a long run to a new addition. Thermostat in the new addition activates fan when the thermostat is set to cooling perfectly. I can use it to manually turn on the fan. ...
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35 views

Weathertron Xl1200 to Nest Thermostat

We have a Trane Weathertron Xl1200 heating pump with the thermostat pictured below and are trying to replace it with our new Nest thermostat. Our old system has a variable speed air handler and we ...
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1answer
43 views

Complete power loss in over-the-range microwave

The over-the-range microwave in my kitchen (GE, 1500W) has completely lost power. The power loss was intermittent for a day, but then at some point it never came back. I have checked all fuses that I ...
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9 views

Manually Toggling Heatpump Reversing Valve to enable cooling

Background A Radiothermostat CT80 fails to signal heatpump cooling, so jumpering the RED node with the GRN (Fan) and YEL (Cooling) node has successfully enabled cooling. The weather became cold, ...
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9 views

Evaporator fan motor does not turn on, could it be thermostat?

If thermostat freezes, will it not turn on the fan motor? It will turn on if I spin it manually. Whirlpool fridge with freezer on the bottom.
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10 views

Thermostat frozen over

I have a whirlpool fridge, with freezer on the bottom drawer? Freezer part freezes, but does not throw cool air to fridge part. Took apart freezer to check fan motor, spin the fan blade manually and ...
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21 views

No furnace fan in cooling mode while hooked to a fresh air damper controller

I added a fresh air damper and control, ( Soler Palau MD6-ES24VK) to my furnace (2006 York GY9S). The damper worked great in the winter but now that I am doing some cooling, I noticed that the outside ...
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47 views

Thermostat Upgrade, furnace C-wire reading low voltage

OK so here is the scenario. Upgrading thermostat from dumb to smart (Ecobee). I've done 2 others in my house that required re-wiring so I have a good sense for what should be done but I'm stuck. My ...
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1answer
74 views

Direct Wiring (bypass thermostat) of heatpump cooling

Last September my CT80 radiothermostat would not signal cooling despite the measured temperature exceeding the temperature setpoint. It would be nice if a relative could manually switch the cooling ...
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20 views

CT80 Thermostat Wiring Diagram Selection

Which terminal should the brown wire be connected to the RadioThermostat CT80? The original thermostat was wired as depicted: The brown wire is connected to terminal E (not F). As I understand it: ...
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27 views

Are my new thermostats compatible with my system?

My two old Lux Pro PSP511LC are dying (LCD going out on both!) so I got two new thermostats from a friend he didn't need we both thought I could use. They are the Orbit Clear Comfort 83521 thermostat. ...
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21 views

Nest E without common wire stuck in purge loop as soon as the Rheem heat furnace ignites

I have a honeywell hz432 and just installed a few NEST thermostats with a common wire and they seem to run fine. I added another NEST E thermostat, but this one didn't have a common wire, and when it ...
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31 views

Smart thermostat that accepts TWO heat inputs?

I have a center split ranch that uses baseboard heating. The heat is divided into two zones, so the boiler is currently controlled by two different thermostats. And that has little to do with the ...
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22 views

Thermostat with an external transformer

I am trying to hook up a Vine TJ-610B-W WiFi thermostat to my heater. The original thermostat had only 2 wires, hooked to R and W, none hiding in the wall. I plan to use an external transformer for ...
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1answer
217 views

C wire - thermostat - not providing power

I'm replacing my old Honeywell thermostat with a new Wifi thermostat. My old/current one is battery powered and doesn't use the C wire. I found the C wire behind the plate. I connected the c wire to ...
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37 views

Help adding C wire to furnace - Heat only system

Looking to add C wire into my furnace. Heat is currently running on two wires with older thermostats. Luckily the in wall wiring has three wires. Any help to point out the C wire for my setup? Or ...
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42 views

turn on furnace blower with temp sensor

I have a wood stove in my finished basement. I am looking for a way to turn on the blower fan of my furnace once the temperature in the basement reaches a certain setting like 75 degrees, that is ...
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1answer
51 views

How Do I Wire A Toggle Switch between (2 ) 24V heating only thermostats to switch between thermostats?

I have a gas-fired forced air furnace which I need to control two separate heating zones from. One zone is to heat a crawl space only to 45 degrees and the other is the space temp of the cabin. I ...
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1answer
68 views

Bad gas furnace install?

I just got a high efficiency condensing gas furnace installed. I feel like it was done poorly, but I'm not sure. Some questions I'm wondering about are: Do furnaces need to be level? It is visibly ...
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1answer
22 views

Main burner in NG fireplace goes out

What could be the reason of main burner going out intermittently. The pilot stays on. The voltage of the thermopile is 638mv when burner is off. The thermostat is a manual heat only. When I short out ...
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8 views

Jumping AC fan to separate Gas Boiler Heat

I have 4 zone boiler/baseboard heat and a new Trane XR 5ton central A/C system. I also have a woodstove that is mainly used for heating except at night when the upstairs are closed. I just got the AC ...
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1answer
43 views

how to connect C wire for ecobee lite to Weil-McLain EG Series-5 gas steam boiler

I want to upgrade from a battery powered Honeywell thermostat to an ecobee3 lite. This is for heat only. My current Honeywell has two wires: Red and White. Missing is the C cable. There are enough ...
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112 views

Using T-Terminal for C-Terminal on Lennox Furnace — Thermostat will not power

Furnace: Lennox Pulse Thermostat: Honeywell RTH6500WF I have the similar setup as the person in the below link Can I use the T terminal in my furnace as the C for a Wifi Thermostat? When I ...
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15 views

how to communicate thermostat to turn on wood heat system when during heat pump defrost cycle

I have physically disconnected the strip heaters in my air handler but the fan still runs which I do not want. I have a wood boiler I want to run in place of the aux heat Can I disconnect the white ...
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19 views

Not sure what colors go to my new thermostat

Not sure what colors go where from my old one to my new one the old is on top and new is on bottom
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14 views

Lost on how to set the comfort range

I am hoping someone can help me. I have read through the questions and answers on here but I am still lost. I have the same GeneralAire M3 thermostat and it does not indicate to me what the percentage ...
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229 views

Nest 3rd Gen 24VAC two transformer issue

Hopefully this will finally solve the issue with my Nest. I bought a Nest 3rd Gen Learning Thermostat and followed the instructions to the tee. I have a two transformer system (Forced Air A/C and ...
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21 views

Furnace, heating when thermostat is at much lower

I have an oil furnace that heats the house with water pipes, and heats the hot water used personally. There are two thermostats used, one for the house and second for the back porch. The issue is ...
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30 views

Fan Blows Constantly Even With C Wire

Nest stated that my furnace only set up (we have an evap cooler) would work with their Nest E product. I self installed only two wires, R and W. The heating works; however, the fan always blows ...
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93 views

Nest thermostat installation to furnace and heat pump

We have T874G1196 thermostat by york (can only find honeywell documentation) MB7BM-1200K-B air handler H8HK015H-21 electric heater Thermopump (heating and cooling) We want to connect it to a nest ...
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36 views

How to identify a c wire?

I have 3 wires coming out from the wall at my new house (red, white, blue). It is a water boiler heat only system. The tstat was already removed unfortunately. I thought the blue wire was the C wire, ...
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50 views

Heating System Premature CutOff / DIY Options?

I've collected all of the facts about my system and the problem we are seeing. We have two external air pump units outside the house and a Rheem furnace (GH36S, 36000 BTU) that appears to be working. ...