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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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Where to connect Blue C Wire at old furnace?

I have looked at other responses and each layout is a little different. Looking to connect a Smart Thermostat and need to know where to connect the Blue wire at the Furnace. See the attached picture....
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2answers
37 views

What's wrong with my heater?

My heater only turns on if the temperature inside the home is 68 degrees or above. If the temperature inside the home is below 68 degrees, I can hear the thermostat click when I turn on the heater but ...
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1answer
37 views

Figuring out electrical connections for THREE electric baseboard heaters with single pole thermostats

I recently purchased a home (triplex) and in the basement unit, which is a one bedroom apartment, there are three baseboard heaters (bedroom, washroom, and living room). The issue is that the living ...
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0answers
23 views

How can I install a Y wire for a Nest thermostat?

Installed a new Nest thermostat yesterday. My setup is a 4 wire system. Green, Blue, White, and red. I have central air and gas heat. They had the Blue wire "C" into the Y for the AC. Since the Nest ...
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0answers
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Nest E without common wire stuck in purge loop as soon as the Rheem heat furnace ignites

I have a honeywell hz432 and just installed a few NEST thermostats with a common wire and they seem to run fine. I added another NEST E thermostat, but this one didn't have a common wire, and when it ...
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10 views

VENSTAR T2800 thermostat “dark” and unresponsive [closed]

Thermostat not working, no battery in unit, NO HEAT!! Help
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0answers
21 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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0answers
20 views

Ecobee install with AC system disconnected

My house which was purchased from a bank (foreclosure) was originally wired with both central air and heater (forced air). But when the previous owner left, he took the air conditioning unit. The ...
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1answer
26 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
25 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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1answer
32 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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2answers
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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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0answers
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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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1answer
31 views

C wire - thermostat - not providing power

I'm replacing my old Honeywell thermostat with a new Wifi thermostat. My old/current one is battery powered and doesn't use the C wire. I found the C wire behind the plate. I connected the c wire to ...
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1answer
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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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0answers
54 views

C-wire on Weil-McLain CGA Series 2

I have an old thermostat with only 2 wires connected to my Weil-McLain CGA Series 2 boiler. I would like to replace it with a Nest thermostat. I need to add a C-Wire in order for it to work. Luckily, ...
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32 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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24 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
68 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
33 views

How Do I Wire A Toggle Switch between (2 ) 24V heating only thermostats to switch between thermostats?

I have a gas-fired forced air furnace which I need to control two separate heating zones from. One zone is to heat a crawl space only to 45 degrees and the other is the space temp of the cabin. I ...
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1answer
38 views

Bad gas furnace install?

I just got a high efficiency condensing gas furnace installed. I feel like it was done poorly, but I'm not sure. Some questions I'm wondering about are: Do furnaces need to be level? It is visibly ...
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1answer
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Swapping to Hive thermostat. 4 wire communicator has 2 wires per post

I'd previously asked if I could swap my wires from the 4 wire communicator to the larger board and was told I could. I finally found time to do it. However, as I was preparing to move the wires, I ...
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1answer
61 views

Can't get wifi thermostat to work with gas boiler

I bought a Sensi WiFi thermostat and I have been trying to install it. I can't quite figure out how this wiring should work. Here is a link to pictures of the boiler and the current thermostat. The ...
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1answer
32 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
33 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
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Main burner in NG fireplace goes out

What could be the reason of main burner going out intermittently. The pilot stays on. The voltage of the thermopile is 638mv when burner is off. The thermostat is a manual heat only. When I short out ...
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1answer
34 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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0answers
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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0answers
67 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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1answer
21 views

In floor heating GFCI thermostat failure?

Fifteen years ago, a contractor installed Easy Floor heating system under tiles in our lower level. There are four GFCI programmable thermostats wired to 240v service. About five months ago, one of ...
2
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1answer
31 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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1answer
24 views

how to connect C wire for ecobee lite to Weil-McLain EG Series-5 gas steam boiler

I want to upgrade from a battery powered Honeywell thermostat to an ecobee3 lite. This is for heat only. My current Honeywell has two wires: Red and White. Missing is the C cable. There are enough ...
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44 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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1answer
52 views

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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0answers
13 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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0answers
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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0answers
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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
34 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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0answers
50 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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0answers
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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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0answers
23 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
38 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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0answers
26 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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31 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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0answers
45 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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0answers
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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0answers
26 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
37 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
47 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
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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 ...