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Questions tagged [thermostat]

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

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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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190 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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377 views

Help with smart thermostat wiring

Installing an ecobee4 thermostat. Have a 2 stage furnace with ac. Had a Trane furnace installed couple years ago and just noticed it's jumpered between W1-W2. Old thermostat wire was only 4, ...
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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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361 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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123 views

A/C Electric Blower Motor issue

My A/C system uses an electric furnace blower motor for heating and cooling. The motor jerks violently when cycling off when the thermostat is set on auto for cooling. The motor was recently replaced ...
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2answers
909 views

Where to connect C-wire on old furnace (diagram attached)

I've got an old steam furnace and would like to add a common wire. The wire is already ran, I just have no idea where to connect it. I thought it would go to TR but that didn't work. Thanks in ...
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372 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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734 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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152 views

Why my thermostat is cycling on and off immediately?

I have gas 80% furnace and is controlled by Honeywell thermostat (rthl221b1008). It didn't use to do this before, but it is acting weird for the last day or two now. It would run for about 10 minutes ...
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ecobee3 thermostat on old 2-wire boiler

Situation: 2 lugs on boiler control, one I'll call "red" or "R" that comes from the built-in transformer with ~14v and one I'll call "white" or "W" which, when jumpered to R, turns on the boiler. ...
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487 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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143 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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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 ...
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Can the cooling wire (Y) be used to activate the furnace fan with a programmable thermostat?

Simple question I think, but you guys make the call. Can the cooling wire (Y) be used to activate the furnace fan? My neighbor has a Honeywell RTH7400 programmable thermostat used for natural gas ...
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Multiple C wires? [duplicate]

I recently received a wifi enabled thermostat which I thought I could install easily since I saw an unused wire (Blue) which I assumed would be the C wire behind the current thermostat. When I went ...
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732 views

How to wire A/C Thermostat given different wiring conventions

I've just moved to a new apartment in which I'd like to replace the current central A/C thermostat with a new one with WIFI control. I hope it's possible! I have basic diy electric skills but no ...
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1answer
345 views

Wire in parallel thermostat and timer to an air extractor [duplicate]

as the title: i have a room with with a heat generation that i need to keep under a certain temperature. Anyhow, i want to grant a minimum of air circulation even if the temperature is not reached (...
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470 views

Temperature of water in the shower fluctuates - will a cheap thermostatic tap help?

I recently moved to an apartment where temperature of water in the shower fluctuates and we called for a plumber. He either cleaned up or replaced one part (I think it was the mixer - nothing visually ...
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3k views

Nest thermostat - combi boiler and UFH set up question

We recently had some work done, a new open plan room, a new boiler and underfloor heating (UFH) put in. We had some confusion, a lot of which comes from not having a basic understanding of how the ...
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2k views

Add a c-wire to 25+ year old Rheem furnace

I've looked at just about every post on adding a C-wire to power a WiFi thermostat but remain uncertain on how to proceed. The current installation on a Rheem RGAC-080A is two wire as here: XFMR - ...
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Can I shorten my in floor heating cable?

Just wiring up an in floor heating thermostat. I have two separate two wires going into my flooring as well as another coming from the panel. I am wondering about the two wires going down to the ...
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5k views

AC Compressor outside is not running with new thermostat

my old thermostat stopped working, so I purchased a new one to replace that. The old one was powered by two AA batteries. A green wire connected to G, a white wire connected to W, a blue wire ...
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1answer
1k views

Changing Trane Baystat240a to another thermostat

I want to change my current thermostat to a programmable electric one (no batteries). Could someone verify if it does have a common wire and if all wiring could fit modern thermostats? Looking at the ...
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423 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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55 views

Thermostat needs to be set very high to work

Our home thermostat is behaving strangely. Let say it shows that the current room temperature is 60F. If we set it to 63F it will start the Fan (ventilation) but will not actually start the heating so ...
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Honeywell WiFi Smart Thermostat Wiring

The Honeywell WiFi Smart thermostat was operating fine when on AC until the heat went on this fall. Now, each time the fan goes on, the thermostat loses the connection, turns blank, then reboots ...
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466 views

My attic unit already has a wire connected to C, can I still connect a wifi thermostat? [duplicate]

I have an extra wire I can use for the C wire on both ends but in my attic the main unit has a wire already attached to the C spot and going away from the unit to something else. Can I attach two ...
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1answer
2k views

How can I install a Honeywell RTH65800WF Wifi thermostat?

I am having some difficulty figuring out the correct wiring for my new wifi thermostat. Before I bring out the A/C technician, I was wondering if anyone here might be able to help? Searched other ...
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62 views

Keep finding thermostat on heat

On multiple occasions now, I have noticed odd things going on with my HVAC system, only to go to the thermostat and find that it has been set to heat! This happened once in the middle of summer, when ...
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541 views

Thermostat replacement

My old thermostat is a carrier t-stat and has a jumper wire between o/w2* and L I am upgrading to a honeywell wifi t-stat, should I install the same jumper wire on the new thermostat? I have an ...
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177 views

Connect Taco Radiator system to a new Honeywell wireless thermostat

I have a Taco model 572 valve connected to an existing wired Honeywell TH8110 thermostat for my oil fueled radiator system. I'm getting a new Honeywell TH6320 wireless thermostat for a new A/C ...
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163 views

Which wire is the C wire?

Model: Goodman AWB30-08C Electric AC/Heat I'm hoping someone can help me identify the 24V C wire. Fortunately the thermostat line has a spare wire already run, so I just need to find the C wire in ...
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2k views

Master-Slave type Thermostat?

I have 4 thermostats located in four different zones and a separate AC thermostat. I want to get some programmable thermostats for each location. I could buy 4 individual programmable thermostats ...
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1answer
2k views

Is it possible to use add-a-wire with my current configuration to add a C-Wire? [duplicate]

I only have four wires: Red, Blue, Yellow, and Green. My old thermostat jumps the R to RC and leaves C empty. I have a new thermostat that wants 5 wires, but I don't have C. I am not sure what the ...
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why does my heat pump wiring diagram show 7 wires going to the thermostat but the thermostat only says it needs 5?

Here is a link to the wiring diagram for my heat pump. The thermostat that I am planning on buying has the following terminals C, G, Y, O/B, RC, R, Aux, E, and L. The instructions say to jump the RC ...
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79 views

Can I use a transformer to power a thermostat? [duplicate]

So I bought a Nest Thermostat off amazon, I read they used batteries and what not and after I purchased it I was looking at the description on amazon and it said it was a built in rechargeable battery ...
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2answers
1k views

No electricity going to thermostat

Our old thermostat is working but I want to change to a new one (nest thermostat). I have two exact HVAC unit at home. I change one it works but when I change the second one it doesn't work because ...
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976 views

How can I add a C-wire to a Venstar T5800 thermostat?

I am trying to replace my existing thermostat. My old thermostat has: Rh, W (coming from the heating unit). Rc, Y, G (coming from the AC unit). On the Venstar T5800, I can map as follows: Rh+Rc -...
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730 views

Why isn't my thermostat working?

I have an old Lennox (gas heat only) thermostat. There are 3 wires coming from the wall. Black, yellow and a light blue color (could be a faded green or an old dirty white). The thermostat wouldn't ...