Questions tagged [thermostat]

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

257 questions with no upvoted or accepted answers
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59 views

Very Old thermostat with TR wires

I want to buy a new smart thermostat, but am confused on the old wiring. I have single zone 120year old gas boiler (converted from coal, then oil, now gas). No cooling. The old honeywell thermostat is ...
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208 views

Nest Thermostat E wiring with a C-wire adapter

I wanted to get a Nest Thermostat E, but my current thermostat doesn't have a C wire. From what I read online, it's better to use a C wire, so I was considering adding a Venstar Acc0410 adapter. ...
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139 views

PTAC heat troubleshooting

I own a condo with two Islandaire EZ09EBMXH8N10AA PTACs, one of which is acting weird. They have self-contained A/C mechanisms, but the rooms are heated by pumping hot water from the building through ...
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29 views

Pretty basic Honeywell Wireless Thermostat Questions

I thought I knew at least the basics of how the Honeywell Thermostat worked, but testing with a multi-meter dashed those presumptions. I have another question posted, but until I get the basics ...
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1k 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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3k views

Carrier Furnace (6-wire) to Honeywell thermostat --> no cooling :-(

Carrier Furnace w/ Honeywell WiFi Thermostat I have a Carrier furnace with the cheapest programmable thermostat (TB-PHP01) that came with my house. The thermostat uses six wires: Y, C, R, G, W, and O. ...
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53 views

Separate Thermostats for Heating and A/C

I recently purchased a vacation home that has two thermostats for a forced hot air gas furnace and a separate A/C unit that shares ductwork. The A/C also cools better when both the A/C and furnace fan ...
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99 views

AC unit not turning on

My A/C doesn't come on when I set the temperature on the Braeburn thermostat very low. Also, the recirculation fan doesn't come on when I set the thermostats fan setting to 'on', as though the indoor ...
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1answer
2k views

Converting I+ I- thermostat to 'standard' wiring

I've been replacing my thermostats with the RadioThermostat CT50, which reports to my home-brew home control/alarm system. I have a 3-year old AireEase 4-ton unit in the shop that has a Comfort Sync ...
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1answer
79 views

Hook up new thermostat

Top brown picture is my old thermostat white is the new one , do I have it wired correct? On out side unit we have replaced motor, fuses, compassator ,cc contactor ,relay . We have a heat pump. But ...
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175 views

Controlling one FCU with two thermostats

I have a chilled water fan coil unit that will feed two areas, living and the bedroom. I want to control the FCU with two thermostats, one in the living and one in the bedroom, (preferably) in a ...
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1answer
2k 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 ...
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1answer
90 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
14k 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 ...
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1answer
45 views

How can I control my furnace fan from a secondary thermostat?

I have a WaterFurnace geothermal system with upper and lower level zones. I recently added an outdoor wood burner and my issue is that I want to use a secondary stat to run the furnace fan during the ...
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101 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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31 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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1answer
2k 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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196 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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56 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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52 views

How to Run Fan Only with Thermostar Furnace With G Wire

I have a Thermostar Furnace that works great for Heating our home. We do not have AC and do not want that. But, we do want to be able to just run the fan without heat. The W and RH wires were ...
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1k views

Where should I connect my C wire on Goodman GMP075-3 Rev.B

I am trying to install an ecobee4 to replace a digital battery powered thermostat. I removed the existing thermostat and found that there was a spare blue wire that was wrapped around the others that ...
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1k views

How to wire a Taco zone valve controller with ecobee

I'm having an issue with wiring my Weil McLain gas boiler. It was wired up fine and working for a single zone. I added (2) 4 wire zone valves in. So I now have 2 zones, a Taco zone valve controller(...
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20 views

Do I need to replace the thermostat wiring leading to my boiler?

I have a boiler in an old building with four different apartments. There are two thermostats that call for heat from the boiler, and valves that direct the hot water to the respective part of the ...
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1answer
607 views

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

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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289 views

Changing AC Fan Motor/Capacitor with No Luck

Issues with a central AC unit: Turned it on and heard a buzzing sound, but the fan didn't start. Started by looking at the dual capacitor. We happen to have two identical units, so I tried the ...
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35 views

Portable heat pump strange thermostat

I've got an Olimpia Splendid Ellisse HP portable heat pump with strange/incorrect thermostat readings. According to another thermometer the room temperature is currently 16.9C, the heat pump ...
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294 views

Nest + opentherm + zone valve

I have a Nest 3G, I'm now considering to change my boiler due to age-related issues. Can someone tell me if I can connect the Heat-Link to both zone-valve (on/off contacts) and boiler (OpenTherm). I ...
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84 views

Smart Thermostat (Nest, Honeywell or Ecobee) from KMC wiring?

I moved into a 1br condo recently and was looking to update the thermostat to Nest (or other Smart home thermostat). The current thermostat model is KMC and when I took off the casing, the wiring does ...
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1answer
8k views

Honeywell RTH6500 WiFi Thermostat wiring questions for a heat pump

I'm trying to install a new Honeywell RTH6500 thermostat on an old heat pump system that has regular plus emergency heat and the closest matching diagram says to put both the white "W2" wire and black ...
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45 views

furnace wont kick in

My furnace seems to work intermittently. overnight its seems to stop... i have checked the thermostat and it shows says it is heating. fan is on auto, but nothing coming out. when i turn heat to off, ...
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4k views

Nest thermostat - electrical buzzing/humming noise

I have recently installed two nest thermostats (the black gen 3, and white model E). The system is gas radiator heat wired to the model E via the usual Rh and W wires, and Rh, Rc, Y, G, W wired to the ...
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806 views

Voltage Drop between W1 and Rc wires

I recently converted from Oil to Gas. One of my zones is no longer working post conversion (it was working, then nothing worked, and then after they replaced a defective unit on the boiler it didn't ...
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426 views

3 wire heating system, has 3 unused wires with 16v, can any be used as a common wire?

I hopefully have a quick question. I am thinking of getting a Ecobee or Nest smart thermostat, but doing my checks/research before getting one for this house. I rent, so I can only do minimal changes. ...
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248 views

Thermostat for my furnace has no power during fan-off delay?

I have an older Tempstar 5000 furnace and a newish Honeywell wifi thermostat. The furnace works fine and the thermostat appears to be wired correctly (4 wires including C wire) but for some reason, ...
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90 views

B and Y wire connected to Y terminal?

Is it common to have the blue and yellow wire both connected to the Y terminal in the thermostat? I went under the house and looked at the HVAC unit and it looks like blue is connected to C out of the ...
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1answer
1k 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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2k views

Installed new Sensi Thermostat, Everything Works Except No Cold Air

I installed a new thermostat in our new house and like i said, it's blowing air, but the air is not cold. Here's how it was set up when it was working: Here's what Sensi said to do on the app as I ...
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2k views

Controlling 110v swamp cooler(Mastercool) using Nest thermostat

Afer hearing many great things about Nest Thermostat, I decided to buy the 3rd Generation Nest thermostat. But after doing much research, I came to know that my MasterCool Swamp Cooler will not work ...
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13k views

'Wait' indicated on my Honeywell RTH7400 thermostat after 1 week vacation

New Homeowner (December) and I need help troubleshooting. Everything was peachy keen until I returned from a week vacation. A/C will not cool, but fan will turn on if I take it off of auto. "Wait" is ...
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1k views

Should I pull ethernet cable to my thermostat?

I'm going to be installing an ecobee3 smart thermostat, and need to pull some additional #18 thermostat wire. Since I'm going to be pulling cable anyway, and I have a box of cat 5e ethernet cable, ...
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207 views

Can I usefully control an electric baseboard heater in 1 room with the same thermostat as my central heat?

My house has a gas furnace and heat pump (and AC). Unfortunately, one bedroom does not have air ducts hooked up. Is there a way I could install a baseboard heater in that bedroom and have it ...
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79 views

What is this device connected to my HVAC unit?

I have this device connected to my HVAC unit in my apartment. I only have it in two of my rooms. In one of the other rooms I do not have this unit and was able to install an ecobee seamlessly. However,...
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362 views

Installing new thermostat without a C wire. Can I use my heater/R wire instead? Random 13V as well

I'm installing a thermostat, but I don't appear to have a C wire. My old thermostat had R/RH,Y,G,and W. It's an AC system that was setup before I got here. The actual AC unit is a long way away and ...
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54 views

Added load to thermostat circuit?

I have a couple Nest thermostats that I want to power when my boiler is powered off. My plan is to hook them up to a 24v transformer using the existing R/W wires (no C wire and I don't want to run ...
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661 views

Adding a C wire

I know this question has been asked multiple times and I'm going to try some of the methods I have read in other threads but wanted to ask this question since I didn't see anyone else's wired the way ...
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2answers
5k views

Why might a thermostat refuse to switch from Heat mode to Cool mode?

I have this Honeywell RTHL2410C programmable thermostat and typical Florida electric AC system. Starting this Spring, it has started behaving strangely when switching from Heat to Cool mode. The ...
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78 views

Possible of override 2 zones with one thermostat

I have a vacation home with 2 zone heating. In the winter, it would be nice to be able to have remote access to the thermostat and 'turn on the heat'. Normally when vacant the 2 zones will be set to ...
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1answer
520 views

Why might a central heating programmer no longer override a room thermostat?

My central heating and hot water is governed by a Danfoss FP715 Si. Using this I can set the time each day when the central heating and the hot water come on and off. When the central heating is on it ...
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9k views

My furnace has a C - common wire but air conditioner uses it - how to hook up smart thermostat?

I bought an ecobee3 smart thermostat which requires the C wire. At my furnace there is no circuit board but there was a diagram and I was able to locate the C - common wire, but it seems to be used ...