Questions tagged [thermostat]

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

217 questions with no upvoted or accepted answers
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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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22 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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35 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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39 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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52 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. ...
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17 views

Mercury thermostat behaving strangely

I reinstalled an old mercury thermostat. Heat and air both work, but they won't cut off until I move the thermostat switch to Off. In other words, when the switch is on Heat, the furnace and blower ...
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42 views

Lennox G12D2E-55C-6 with a Johnson Control G779LHA-1 ignition control and Mercury Thermostat

I am looking to replace the mercury thermostat with a Lux Kono thermostat simply to have the ability to run the fan only and circulate the air. I believe this thermostat does that periodically. I'm in ...
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32 views

AC Common wire disappears

On my furnace there is a wire that is labeled C/Common. But at my thermostat there is no common wire. Wires on furnace control panel: W - White Y - Yellow G - Green C - Common Wires at my thermostat: ...
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25 views

thermostat issues with honeywell

I've gone thru 3 thermostats in the last 6 months, and the temperature on them goes wacky. I've tried everything except call someone. is there a trick or solution. this is the third honeywell ...
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44 views

Can a Nest work in my setup (or am I stuck with Lyric, as they claim)?

Before crucifying me for the subjective question let me clarify that my question is quite specific if you read on. I bought an old home with bad insulation and a 55-year-old furnace 3 months ago. I ...
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24 views

Need C wire for Nest thermostat with zones. From zone panel to thermostats?

If I have a C wire connected from the furnace to the zone panel (but not to the thermostats), do I only need to run new C wires from the zone panel to the thermostats?
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44 views

Temperature monitoring for storage hot water system (RP-2 connection)

My HWS has a secondary outlet connection I don't use, and I'd like to use it to install a thermal probe I can monitor. HWS RP ¾ / 20 temp probe? Does anyone know of a practical way to install a ...
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199 views

Connect Wifi Thermostat to Goodman GMP050-3?

I'm trying to connect up a wifi thermostat to Goodman furnace, specifically the GMP050-3. I've done some reading on this but I'm still not quite sure how to go about it. Specifically, I'm not sure ...
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269 views

Nest for this setup

Is this the correct wiring setup for nest.
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167 views

Wiring for a new honeywell thermostat

I am trying to install a basic Honeywell Programmable thermostat, but the wiring is a bit different, and I am reluctant to start taking it apart. I have a Goodman heat pump, which is occasionally ...
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73 views

Identify furance/cooling system from wiring?

Is there any way to tell the heating/cool system you have from the wiring? I have a Honeywell th6320wf02 that was correctly working and then I accidentally overwrote its system type. It's wired like ...
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55 views

Two Separate Systems on one Thermostat?

I have a baseboard hot water system and a separate gas furnace with heat and AC. Thus far, they have been on two separate thermostats. Is there a way to put them on one thermostat or is there a ...
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42 views

Is my control board bad?

I have a Goodman evaporator/gas heating unit that runs the central fan motor constantly after it is powered up a couple of seconds. This happens regardless of what wires are hooked to the control ...
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189 views

Connect C wire to Carrier board

I got Carrier board HK61EA010 and extra C-blue wire that is not connected to the board. I wanna use this wire to power WI-FI thermostat. I cannot find the manual for this board. Does anyone know where ...
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2k views

Where to connect my “c” wire on the boiler side. Weil mclain gas boiler

Im just curious if the “c” terminal on the plug in relay is where im suppose to connect my “c” wire on the boiler side. I have 18/5 wire ran already. Just need to find out where to terminate. To the ...
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64 views

Furnace and Thermostat Issue

One day my parent's furnace and thermostat stopped working. The thermostat is a smart thermostat that depends on 24volts to the R and C wire. We measured voltage between the R and C wire and was ...
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2k views

How to wire C wire to the transformer of HVAC?

How are you all doing? I tried to connect the digital thermostat (Ecobee3) instead of my old honeywell thermostat. The original wiring is below (figure 1) HVAC is located on the ceiling of bathroom ...
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297 views

Master thermostats on a multi zone heat system

I have a 5 zone split level house with forced hot water heat. The issue I’m running into is that my house has an in-law apartment that I rent out and it occupies 2 of the 5 zones, and the other 3 are ...
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1answer
238 views

Replacing old thermostat with 2 white wires for zone boiler heat

I am replacing our basement thermostat that had a white and orange wire together and a white and blue wire together. That is all there is. I ham trying to put in a heat only non programmable honeywell ...
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56 views

Thermostat & transformer

I want to ensure I'm safe. Is it normal to find fluctuating 12 volts when the thermostat (2-wire heat-only) is at "rest" and not calling for heat? The thermostat appears to function normally with a ...
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775 views

How to insulate a thermostat

Some previous owner of my home moved the original round 2-wire thermostat to a wall of the vertical chase used for the hot water heater vent, the gas lines, etc. The wall is quite a bit colder than ...
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802 views

Need Help on Adding a Common Wire for Nest

I recently purchased a Nest thermostat. After couple weeks of usage, the Nest is constantly shut down due to low battery. I search online that adding a common wire is the go solution for this. However,...
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1answer
110 views

Ecobee3 lite connected to Lennox Pulse G14Q Heat/Air Condition

I have read a similar wifi thermo connection feed here and they had success hooking the C wire to the T terminal on the furnace. I can get power to run the thermo from the T terminal, but when I do, ...
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1answer
192 views

Ecobee3 Setup and furnace only has W G R

My existing thermostat has 4 wires (missing C) so I'm attempting to use the Power Extender Kit (PEK) at the furnace control board. Only problem is, I only have 3 wires that are obviously labelled at ...
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1k views

Thermostat won't display temperature and won't control heater (although fan works)

I'm having issues with my Honeywell RTH7600D thermostat. It's a couple of years old and has worked fine until recently. We're in Southern California and the cold weather has recently started so I ...
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1answer
63 views

Rapid on/off cycling of furnace

My 50-year old wall furnace keeps cycling on and off as it gets near the set temperature. Can I fix this by changing to a new thermostat? It's a 2-conductor cable (no blower).
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1k views

fireplace thermostat will turn off fireplace but won't turn it on

I have a propane fireplace that wouldn't start. Cleaned the thermopile and thermocouple and got the pilot to work fine. Then the main burner wouldn't light from the thermostat--it only lit if I jumped ...
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189 views

How to connect wifi thermostat with a boiler after cable upgrade?

I have an old battery operated thermostat right now with two wires (18/2) attached to it running to a boiler. No AC, fan, etc.-- just a boiler. I can easily replace the wire with 18/5 one, however I'm ...
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61 views

My thermostat and heating system was working fine but the batteries read low power

So my Honeywell non WiFi Thermostat was working fine except for the low battery signal in the top right-hand corner. We took the face off of the thermostat of course shutting the Heat and fan off ...
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66 views

Problems with my thermostat

My thermostat will turn on the baseboard electric heater but will keep running till you turn it all the way off.
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359 views

NEST thermostat for hydronic floor heating: the three wire setup

I'm trying to install a 2nd generation Nest thermostat for my hydronic floors. So it's only meant for heating and not for cooling. Someone else removed the old thermostat a long time ago so I don't ...
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33 views

WIFI “C” terminal

I recently purchased a WIFI thermostat that requires the use of the "C" terminal. I do have an extra wire available to use on the C terminal that runs from the wall unit to the furnace. However, ...
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491 views

Need help going from single pole to double pole thermostat

I am trying to replace single pole thermostats with double pole in two adjacent rooms. In each outlet there are three black, three red and three grounding wires. When I removed the single pole ...
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2k views

How to connect Nest thermostat to Evaporative Cooler (Swamp Cooler)

I have reviewed the post here, Controlling 110v swamp cooler using Nest thermostat It discusses how to connect an evaporative cooler using 110v to a standard thermostat. I am looking for a specific ...
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371 views

Help me to find C wire on A/C side

I replaced my old AC only thermostat with Honeywell RTH6580WF smart Thermostat. Also replaced existing 3 terminal wire with 4 for C wire hookup. TSTAT specs h t t p yourhome.honeywell.com/en/products/...
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730 views

Thermostat wiring with external transformer

So I am trying to wire a Honeywell lyric thermostat and I tried following videos but got a little stuck. So I have wires R, W ,Y , G coming to my original thermostat. I bought an 24V external ...
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52 views

Getting 24v for my new wifi t stat

I just got a Honeywell RTH6500 thermostat and I don't think my existing boiler has a spot to hook up a C wire or to get me the 24v I need. Can anyone tell me if I can grab that voltage off of ...
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384 views

Should I connect the white wire to the aux connection on my new thermostat?

I changed my old thermostat to a honeywell rth3100c. I was instructed to attach the white wire to the aux. connection. I do not have a heat pump. all electric system. Is this correct and if so for ...
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485 views

Putting a WiFi thermostat on a Milli volt system control of a fireplace.

I under stand that it can be done using a transformer and a relay along with a WiFi thermostat. I want to keep the present Milli volt thermostat functioning in case I loose electrical power and I ...
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150 views

Why does my non-vented gas fireplace turn off after a few minutes?

I have a non vented gas fireplace, brand new, it has a screen on the front and logs. The pilot light is strong and stays lit, however the main flames turn off after a few minutes even when the ...
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1answer
142 views

Smart Thermostat and 24 volt transformer direct to thermostat

I have a hot water boiler and separate AC system and bought a wifi smart honeywell thermostat to get a C wire- installed a 24 volt transformer that has two wires if one goes to the C where should the ...
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999 views

Honeywell TH6110D1005 Thermostat keeps resetting itself

I have a Honeywell TH6110D1005 thermostat. I do not use the program mode, I keep my temp set to 71° at all times when it is on the Cool setting. Sometimes, it resets itself to 65° for no reason ...
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216 views

How to wire new Honeywell smart wifi thermostate( RTH9590WF) to replace older Honeywell thermostat using only 3 wires

Old thermostat was only using 3 wires, connected to W, G and R-Rc jumper. no C wire. Does have extra wires not being used at each end. Big question is what to I connect to at the furnace for a power ...
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61 views

Why Does My Heil Furnace Start When It Should Be Off?

My Heil furnace starts with the thermostat set to off. I disconnected the thermostat wires at the thermostat and it still starts randomly. I disconnected the heating wire at the board and it still ...
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149 views

C Wire in HVAC Unit

I am looking to install a new style thermostat in my apartment and it requires a C wire. I do have an extra wire run from my HVAC unit to where my thermostat is. But when tracing it back to my HVAC ...