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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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1answer
29 views

Switching from a Mercury Switch Thermostat to a XT500C Thermostat

I only have a white, red, green and yellow wires, from my old thermostat. I see multiple Red wires... where does a single red wire go... to the R connection...
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1answer
218 views

Adding a C wire to older 3 wire

How do I use the green wire as a C wire as suggested in most installation instructions for the newer wi-fi thermostats? They all reference terminal strips at the furnace, all I have is the 3 wire ...
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1answer
112 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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2answers
2k views

Nest thermostat gen 2 won’t turn off furnace

I’m struggling to find a solution for my furnace. It’s an older Lennox furnace and runs fine. The problem I’m having is that it keeps burning up my thermostats and once it does it won’t let the ...
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0answers
51 views

Replacing old thermostat and two unidentified wires

I'm replacing an old thermostat from the early 90's with a new wifi thermostat. When removing the old one, it only used R,G,Y,W wires, and the new wifi thermostat requires a C. After fully removing ...
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0answers
48 views

Only getting 15-16 volts from Furnace R and C

I recently purchased a smart thermostat. Because it needed a common wire and I only had a 3 wire setup, I ran a new thermostat wire to my furnace. However, I now get only 15 volts (inconsistently, ...
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1answer
737 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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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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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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1answer
399 views

Connecting Wood/Electric Furnace to Smart Thermostat

UPDATE: I spoke with an ecobee tech and they pointed me to an alternative solution. If I get an adapter called a "Fast-Stat Common Maker", all I need to do is figure out where to connect the C-Wire ...
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1answer
94 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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6answers
830 views

Why can I not find a 120V programmable 2-pole thermostat

I'm wanting to connect a 120V wall heater to a programmable, 2-pole thermostat. The difference between 1 vs. 2 poles involves whether or not the thermostat can truly, completely cut power or not. ...
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1answer
91 views

Ecobee 3 lite Installation — Confusion about C wire (on furnace but not at thuermostat)

I am about to install the ecobee 3 lite thermostat. On the thermostat end, there is no C wire - just the typical 4 wires - R,Y,W,... On the furnace end though, there is white C wire too, which I do ...
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1answer
975 views

C wire and smart thermostat (with pictures)

I'd like to install an ecobee3 thermostat, but I'm not entirely sure about my wiring. The current thermostat seems to only have a W and RC wire coming into it. There is also what appears to be a blue ...
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2answers
841 views

Installing thermostat - No C wire or C terminal available on furnace

So I've looked through many posts all over reddit and other websites but it seems every furnace is slightly different. I am an early twenties guy who doesn't want to burn down his apartment. If ...
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2answers
14k views

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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2answers
78 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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1answer
45 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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1answer
2k views

Hooking a wifi thermostat to a 2 wire boiler

I'm in the process of figuring out how to swap my existing thermostat for a new WiFi thermostat. Naturally it's connected to my home's boiler by 2 really old cloth wrapped wires. Examening the wires,...
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2answers
27 views

Thermostat settings two hvac units older house

So I purchased a historic house built in 1920. The house has two HVAC units, one for the upper floor, one for the lower. Total sq ft 3300. I had been setting the upstairs thermostat at about 83 ...
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1answer
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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1answer
759 views

How to install a 4-wire a/c & fan thermostat with only 3 wires

My home currently has a central a/c unit which is controlled from an 3-wire old mercury switch thermostat. I want to replace it with a newer Honeywell that requires 4 wires. The existing thermostat ...
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1answer
3k 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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1answer
697 views

Can I run a C wire from Fan Relay

We've just moved into a new home with an heat only, oil, forced hot air furnace. The current thermostats are very old and we'd like to update them to something like a nest. The furnace is currently ...
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1answer
261 views

Old Thermostat with just R and Y wires?

UPDATE: this may be R and V, not R and Y, although I'm still not sure how it was set up. I am replacing an old thermostat in my house (the house is from the 60s, I'm not sure how old the thermostat ...
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1answer
144 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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3answers
32k 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
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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2answers
3k views

Installing Nest 3rd generation thermostat from Old Trane Weathertron Thermostat (Mercury one)

Nest is not detecting Power (Rh) Showing error that power is not connected. Please help. Installing Nest 3rd generation thermostat from Old Trane Weathertron Thermostat (Mercury one) New stat wiring:...
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2answers
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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1answer
240 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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1answer
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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1answer
152 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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1answer
1k views

Why my baseboard heater won’t turn with new thermostat?

I have a pair of electromod basement heater. The label on each of them show them show 750/1000W. Power supply to this is 240V I am trying to replace the old manual thermostat with a progrmabale one. ...
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1answer
51 views

Where does my C wire go in this splice connection?

I'm looking to install the Ecobee3 Lite thermostat. My current thermostat has a blue C wire running to it, so my understanding is the PEK doesn't help because that is used if you have no C wire. On ...
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1answer
148 views

Thermostat C Wire (Possibly Unconnected)

I purchased a Honeywell RTH6500 Wifi Thermostat, which requires a C wire. My old thermostat showed a connected blue C wire. However, it was battery-powered. If I removed the battery, the thermostat ...
0
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1answer
205 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 ...
2
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1answer
415 views

Installing a Hive Thermostat

I purchased a HIVE thermostat and want some assurance before I go about installing this. First of all i was wondering where to put the receiver as I thought it would just replace one of the ...
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1answer
530 views

Is my Nest thermostat wired correctly?

I've been having issues like the heat pump not heating. Now that it's hot outside, my A/C isn't working. Can someone tell me if my Nest thermostat is even wired correctly? If it helps any, here is ...
2
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1answer
533 views

New Thermostat installed but compressor comes on immediately

I have a new Insteon Thermostat that I'm using to replace my prior Honeywell t-stat. This is installed to a relatively new HVAC system (both AC and Heat) that DOES have a "c" wire. I've attached the ...
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1answer
58 views

Another “How do I add ”c" wire to boiler for Nest

I have tried searching this forum and others, but I could not find anyone with a situation like mine. I thought it better to ask here, rather than damage something. I have a Lennox wall mounted ...
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2answers
85 views

Thermostat White-Rodgers 1F82-261 switches to stage 2 heat for no apparent reason

I am running a central heat system that uses a heat pump as stage 1 and a gas furnace as stage 2. The thermostat used is the White-Rodgers 1F82-261 which supports 2 stages of heat. When using regular ...
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1answer
62 views

Connecting Common Wire to Control Board

I have a heat pump and want to add a thermostat that requires a common wire. I have read through many threads that show how to add a wire but I already have a few extra in the bundle so its not so ...
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1answer
45 views

Is the PY4G HVAC unit compatible with Nest Thermostat?

I recently bought a Nest Thermostat and I've had nothing but trouble with it. The main symptom is the fan and the AC compressor won't run at the same time. Power only comes through the green wire, not ...
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4answers
6k views

How to wire a relay for an evaporative cooler to a thermostat?

I have an evaporative cooler with 120VAC control that I want to switch on and off using a relay that is activated when the cool call comes from my thermostat. I plan on just using 1 relay to activate ...
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7answers
107k views

Should I use 12/2 or 12/3 to wire a 220V electric baseboard heater and thermostat?

When I bought my baseboard heaters, thermostats and 220V breakers I was advised to get 12/3 wire. When I attempted to install the heaters I found that the thermostats, heaters, and even breakers have ...
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2answers
326 views

How to hardwire combined HVAC system for cooling?

I had to borrow the Nest thermostat from one of my units for another one where it was more needed, while a replacement is on the way. The unit from which I borrowed is combined HVAC (heat+cool) with ...
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1answer
53 views

Plz help me, connect a common wire for smart thermostat in furnace

I bought a 3rd generation Nest. It doesn’t turn on after I hooked it up. I did research saying I need a common wire as power supply. I have closely look all the wires in my system and drew a diagram....
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2answers
77 views

How can I install a Honeywell Wifi RTH6580WF1001 thermostat in place of a Honeywell RTH2300b?

I have separate heating (hot water) and air handler (cooling System). The current thermostat I'm using is a Honeywell RTH2300B and the new one I want to install is a Honeywell Wifi RTH6580WF1001. The ...
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1answer
376 views

Central Heat Won't Turn On When I Raise the Temperature on Nest Thermostat

I'm sure my heater is working. It's 47 degrees outside, and I'm only a little cool inside. My Nest thermostat is set to 67 degrees. The screen on my app (which agrees with the thermostat) is shown ...