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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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Old thermostat to Hive thermostat

My wife decided we needed a smart thermostat... which means I need to install said thermostat... Currently a Bryant Evolution series is mounted. She purchased the Hive with Hub when it was on sale. ...
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12 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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18 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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11 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
28 views

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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38 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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14 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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20 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
21 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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18 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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29 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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39 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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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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0answers
20 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
32 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
36 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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0answers
16 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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24 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
66 views

Old furnace with no “C” terminal for wifi thermostat

I'm new to this forum and was wondering if I could get some help regarding installing a Honeywell WiFi thermostat that requires a "C" terminal. I currently have an older thermostat that has only 4 ...
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17 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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38 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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13 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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1answer
28 views

nest 2nd gen, no common wire/terminal in the fan coil unit

I'm trying to install an older nest in my condo but it immediately complains that there's no common wire attached (error e24). I opened up the fan coil in my condo and there is no specific terminal ...
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18 views

Hooking up C-wire 24v for Honeywell T5

I’m trying to add a C-wire (extra wire available) and my A/C unit has this electrical panel where the R, G, & Y are hooked up. Is one of these terminals the right place to hook up a C?
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1answer
60 views

What powers a Nest thermostat? [duplicate]

I have an older thermostat I'd like to replace with the more modern Nest thermostat. The online Nest compatibility checker tells me that I have a compatible device. However, I'm not sure how it could ...
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10 views

Wiring Thermostat on heat pump

I have a Lennox Heat Pump. Putting in a nest thermostate. Wiring is not assigned common colors. The attic unit has brown as common, Blue as W1, White as W2. But the current thermostat reverses w1 ...
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1answer
28 views

Install Hive Thermostat - C wire power

I am installing a Hive Active thermostat. My previous thermostat was battery operated and did not use a C wire. However, I found a 5th, blue wire, behind the thermostat so I used that as the C wire ...
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0answers
33 views

Can this mess up my thermostat

I have some people living living downstairs, running a little portable heater all the time, so my thermostat is upstairs and my home feels so much colder up then down, can their heater be affecting ...
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0answers
25 views

thermostat does not accept C wire connected to AC unit

I have three identical thermostats, model Radio Thermostat CT101. Two of them have C wires connected to the burner and work fine. The third one controls a heating zone and also central AC. It has R ...
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1answer
41 views

Will my wiring setup work with the Nest Thermostat?

I would like someone who is smarter then me to let me know if this current wiring setup would work with the Nest Thermostat? Thank you for your help
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1answer
57 views

How do I create a C wire? [duplicate]

My furnace is old and only has 4 wire connections, but I require a C wire. How can I create one based on this diagram? I do have 5 wires running between the furnace and thermostat.
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1answer
42 views

Honeywell thermostat issue

I have a Honeywell thermostat with M-F schedule like so... 6:30 am (wake) - 70 6:45 am (leave) - 63 4:00 pm (return) - 70 9:00 pm (sleep) - 63 The Honeywell actually displays wake, leave, return, ...
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Replacing a thermostat

I am about to install an ecobee 4 thermostat.  I checked the wiring in my thermostat and furnace which was: Thermostat Red to Rh Blue to Rc White to W Yellow to Y Green to G Furnace Red to R Blue ...
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38 views

How can I use home automation with hot water heating radiators?

My apartment (in a condo building) is currently using stationary PTACs (using electricity and hot water), which I'm planning to replace with a split-level A/C system (for cooling) and hot water ...
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37 views

Installing new Nest thermostat, wire help

I bought a 3rd generation Nest home thermostat and attempted to install it last night. I live in a home with a heat pump and whole-home humidifier. Removing the faceplate of my old thermostat revealed ...
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1answer
80 views

nest 3rd generation compatibility with honeywell

My home has a honeywell thermostat (THM5421C)! It has 3 wire: DATA,R and C. Humidifier is Aprilaire 700 Series and Furance is Armstrong A97USMV! furnace side: The wire connection as below: Is it ...
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1answer
26 views

Will a Gledhill Boilermate 2000 work with a Honeywell Evohome thermostat?

Our flat uses a communal CHP system, with a Gledhill Boilermate 2000 in our flat (i.e. we don't have direct access to a gas boiler). We're looking to set up a Honeywell Evohome system consisting of a ...
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0answers
11 views

What is difference between return flow temperature controlled thermostat with control based

I bought Tado smart Kit and wanted to replace my radiator wave controls with smart connected one. However, I was not able to install it. I thought I need an adaptor. When I asked support I got an ...
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0answers
28 views

Installing Honeywell T5 WiFi Thermostat

Hoping someone can help me out here. I am wanting to install a Honeywell T5 thermostat, but I’m a little confused with how to proceed. The kit came with the C-Wire adaptor. I have included pictures ...
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2answers
61 views

Electric Baseboard Heater Thermostat Replacement

My house is mostly steam heat, but prior owners put on a small addition and also turned an upstairs closet into a bathroom. These new rooms have electric baseboard heat. Heaters work fine, but ...
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1answer
30 views

thermostat connections with different size wires

my current thermostat has 14 gauge wires connected to it and the wires are supplying 24 volts to the thermostat. i want to get a new thermostat but will need 18 gauge wires. since the voltage from the ...
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0answers
27 views

Building36 thermostat won't turn off heat

I combined the heat (boiler) with the A/C thermostat and I used the same location that the wires were in when the thermostats were working independently. Heating: RH - Black W2 - White Cooling: RC ...
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1answer
57 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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28 views

Can I use C-wire come from air-conditioner rather than heater?

We have a heater in the basement and the A/C in the attic. The wires from both come to the old thermostat: The cable from the basement has only two wires in it -- the R and W. The C-wire comes from ...
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0answers
37 views

Ecobee Smart Thermostat- Using Room Sensor as primary control

This is ultimately a fairly simple question about the Ecobee3 thermostat and the wireless room sensor functionality, but I'll explain my situation first. Twin home, 2 stories + finished below grade ...
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2answers
45 views

control for attic fan

I have an attic fan with an old (MH Rhodes 90015 /marktime) mechanical timer switch. I want to replace the timer with a thermostat (presumably a line-voltage thermostat). To my surprise, in the ...
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0answers
16 views

15vAC at new lyric t5 using g for c wire

got a Honeywell lyric t5 I'm trying to replace my old mercury style one with in order to try to fix a problem with my furnace. From R to C at the tstat I have about 15vac. Everytime I power on my ...
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0answers
46 views

Hydro air and baseboard on single thermostat?

Just bought a new house and I have a big room that currently has 2 old manual thermostats right next to each other. This room is its own zone. One thermostat goes to the air handler in the attic and ...
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1answer
52 views

Replace existing thermostat with diy solution [closed]

I currently have a wireless Altech thermostat. Is there any chance I can replace it with an diy solution (based for instance on a Raspberry Pi)? The idea will be to only replace the transmitter and ...
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1answer
54 views

Can’t turn off power to thermostat

I’m installing a nest thermostat and trying to turn off power to the thermostat before doing so. I’m using a voltage tester and can see the wires coming in have power. I have two systems, one for ...