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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16 views

New Thermostat Won't Engage Plinth Heating in Kitchen Island

I have two plinth heaters on either side of my kitchen island. Since the rest of the house is hydronic, I presume that these are hydronic (there is a zone valve at the boiler) with electric fans ...
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1answer
46 views

Millivolt fireplace turns on by the thermostat but will not shutoff

I inherited a freestanding direct vent fireplace and I'm trying to get it to work with a thermostat. It functions fine using the ON/OFF/PILOT switch but will not work with a thermostat. It is a SIT ...
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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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1answer
30 views

Honeywell thermostat doesn't seem to be connected to standby generator

Honeywell thermometer doesn't seem to be connected to standby generator. Heater is linked to generator panel, but thermostat loses power with outage. Ideas??Thanks
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1answer
32 views

Heatpump Wiring Color Convention

A heatpump thermostat is to be upgraded. I am unsure of: Which color wire is the Common (thought to be BLUE) Where should the brown wire be connected? (B node?) Is the 'B' node in the photo ...
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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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2answers
111 views

Using a ground wire as a thermostat C

Just theoretically, A C wire is just a return for 24v transformer right? So if you were in a situation where you have access to the slab, or just a standard outlet or switch receptacle could you wire ...
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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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8answers
56k views

How can I use a separate transformer to provide a C wire to my thermostat?

Update 02/02/2019 I appreciate all the responses and help but unfortunately i must have not seen the emails stating there were responses! I am now looking into a NEST thermostat and was curious if ...
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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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2answers
74 views

Two mysterious white thermostat wires in an unfinished wall outlet near the floor — what?

About 10 years ago, our house's builder added a small room above the garage. Since they left in a rush, they left an unfinished wall outlet located 1' above the floor. For 10 years, we ignored it. ...
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1answer
115 views

How to connect c-wire to Burnham Series 2 boiler?

I am trying to install my ecobee 3 light but the previous thermostat did not use any c wire. Fortunately, there was an unused wire in the wall and I would like to set it up as a c-wire. The problem is ...
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1answer
37 views

Propane wall furnace not firing

I have a propane wall furnance that is'nt firing, the thermostat is not appearing to trigger the unit. The pilot is fine and the thermostat is a simple unpowered one with mercury that appears to be in ...
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1answer
189 views

How to remove the wall plate behind Honeywell thermostat

I'm trying to install a smart thermostat. I have a Honeywell programmable thermostat now. However, I found that there's a wall plate in back of the back plate, and it's secured to the wall (not by ...
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1answer
38 views

C-Wire identification

I am interested in replacing an older thermostat with a modern networked 'smart' thermostat \ humidity monitor. That being said, does the photographed thermostat have a C-wire? The thermostat ...
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126 views

Adding C-Wire for Nest to Triple Aquastat Relay L8148J

Need some extra eyes and advice on how to add a common wire to our current boiler setup. We have a Triple Aquastat L8148E that has 2 wire that connect to our thermostat. Like many before me, I'm ...
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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
2k views

Where to add C wire on this air handler?

Thanks for helping me here. I am adding a new wifi thermostat to my system but need to add a C wire directly to the air handler (system is a First Co air handler with hot water boiler for heat and ...
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1answer
85 views

Why is my thermostat turning the heat on too soon?

I have recently come across an issue with my thermostat and when and how my heat comes on. My thermostat seems to be an old round Honeywell. I set my temp at 65 typically. As of last night my ...
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108 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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3answers
3k views

My eq-3 Bluetooth Radiator Thermostat CC-RT-BLE is just showing “UPD”. How can I “unbrick” it?

The thermostat just shows "UPD" and there is no way to return to the operating mode. How can I complete the update when I didn't pair the device before or deleted the device from the app?
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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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2answers
24k views

Why “W” (heat contactor) and “E” Aux Heat connected in Thermostat

I'm trying to update my thermostat to one that has a scheduling feature. My plan is to just copy how it was hooked up in an old 129N Thermostat from Armstrong however, I can't figure out why the "W" ...
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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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1answer
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Can't find HVAC C terminal

Could any of these be the c terminal on my hvac unit? There's already a c wire there, just can't figure out where to connect it.
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2answers
12k views

Can I use the T terminal in my furnace as the C for a Wifi Thermostat?

I've read many posts on this, and believe I know what to do, but want to make sure. My furnace (a Lennox G14 Series) does not have a C terminal which needs to be connected to the C terminal in my new ...
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3answers
49k views

Hvac Fan only blows in 'fan on' mode while heating

Our HVAC Fan only blows in 'fan on' mode while heating. In other words the fan will not blow in heat mode if switched to "fan auto". Both fan on and fan auto modes work when cooling. See image below, ...
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216 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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29 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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1answer
110 views

Zone Controller T-Stat Wiring w/ 24V transformer, isolation relays for 2 zones

I have a new Navien SmartZone+ 6-Zone Control for my boiler-based heating system. It is great, except it provides no power on C. I realize the internet has researched the heck out of adding a C ...
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87 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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2answers
28k views

Correct Wiring for Furnace Blower Motor

After getting my furnace blower motor replaced, it now runs only in the following scenarios: 1. Mode "Cool" Fan "Auto" 2. Mode "Cool" Fan "On" 3. Mode "Heat" Fan "On" In other words it will not run ...
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1answer
758 views

UK Nest Installation - Underfloor heating including floor temperature sensor/cutoff

I would like to use Google Nest with my underfloor heating system which is under a wooden floor. Other thermostats allow the user of a floor sensor which monitors the surface temperature of the floor ...
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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. ...
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35 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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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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54 views

Thermostat has two wires going into C terminal

Trying to help my dad install his new Nest thermostat - for some reason his thermostat has two wires going into the C terminal. I've searched and cannot find any other question about a setup like ...
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1answer
44 views

How long you can keep gas furnance heater bypassing thermostat

Thermostat is broken but needed to heat the house. I decided to jump R and W wires to get some heat this cold night. The question is for how long I can run the heater (gas)? Is it Ok to leave it on ...
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2answers
78 views

Electric baseboard heater thermostat.

My the upstairs of my house is filled with electric baseboard heaters that use these thermostats that are mounted right on each heater. My house is a bungalow and the upstairs gets no heat or AC. ...
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36 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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31 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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2answers
3k views

How can I connect a WIFI thermostat to a Honeywell R845A switching relay?

I'm trying to install a wifi thermostat and it won't power up. The old thermo was battery operated 2 wire but there were spare wires. At the R845A relay, red and white whites connect to terminals 5 ...
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1answer
194 views

Can't get fan working on thermostat

I recently purchased a new thermostat. My old thermostat worked for heat (no AC either) but the fan wouldn't go on when I turned to "On" (in hopes to move some cool air from the basement up during the ...
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23 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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4answers
5k views

Can a wifi thermostat to control milivolt operated fireplace?

Have a propane gas fireplace, controlled by a hand held remote control thermostat. Wish to install a wall mounted wifi controlled thermostat, heat only. Seems that all available thermostats operate ...
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3answers
12k views

Thermostat is completely blank. How to troubleshoot

I have a thermostat that is completely blank (no display). I'd like to troubleshoot it myself even if I do ultimately hire a pro! We're in sunny southern california, so it's possible it's had no ...
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2answers
5k views

Need help wiring a new double pole line voltage thermostat

[ Just bought my first home and this is my first time posting, so please forgive me if my terminology is incorrect. I currently have bedrooms upstairs each with 1 baseboard heater and thermostat for ...
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43 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 ...