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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.

219 questions with no upvoted or accepted answers
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87 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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36 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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45 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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1answer
259 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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27 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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352 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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1answer
53 views

Finding Common Wire on Laars JVT boiler

Replacing mercury thermostat with wifi. I have just a red and white wire connected to current thermostat and boiler. There is a green present, but it isn't hooked to anything on boiler. So I can ...
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472 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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16 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
392 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
90 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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154 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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95 views

Correct wiring for Nest thermostat with dual HVAC system

Trying to wire up this new-fangled Nest Thermostat E (the cheapy edition) to my home HVAC system, but unsure of what to do. At the thermostat, I have G, W, Y, R, AND Rc wires, but the R and Rc wires ...
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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 ...
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2answers
838 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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29 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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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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67 views

Is this line voltage thermostat sufficient?

I'm replacing a bad Aube line voltage thermostat for my electric baseboard heaters. I liked the model, so I purchased what I thought was the same one - however I missed a letter in the model. What I ...
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226 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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70 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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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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1answer
5k 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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43 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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3k 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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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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517 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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364 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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2answers
1k views

Why does hot air from my fan heater stop after 4 to 7 seconds?

Product: Challenge fan heater: model E9907R-N -- 230-240V -- 50 Hz -- 2750-3000W. While off, something fell through the grid. I opened the fan heater to remove it. It now doesn't blow hot air (...
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208 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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86 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
694 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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845 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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1k 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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10k 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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606 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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181 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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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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1answer
615 views

Wiring a C (common) wire to a Triangle Tube Prestige Excellence 110?

Wiring noob here. Can someone give me step-by-step instructions for where and how I should attach a C (common) wire to a Triangle Tube Prestige Excellence 110 boiler for a ecobee3 thermostat? I think ...
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78 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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335 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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53 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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604 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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106 views

Thermostat replacement in a double wide

We have a new double wide and I want to replace the thermostat with a new programmable one. We took off the old one and it has 3 red wires, 2 yellow, 1 white and 1 green. I get the 2 red indicate a ...
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645 views

Honeywell WiFi thermostat newly installed--not working

I just replaced a 2 wire thermostat with a wifi one that required a c wire. There was an unused blue wire which I attached to the C connector on the transformer at the furnace. At the thermostat, the ...
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3answers
1k views

Boiler heating extra zones

Background: This is a new house, with a boiler system I'm not familiar with. Instead of zone valves, each zone has its own pump (4 zones). There is a fifth pump on the other side of the boiler. Not ...
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69 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
395 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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1answer
692 views

Need help adding a C wire for a wifi thermostat

With the increasing popularity of wifi thermostats I know this question has been asked many times, however I'll ask it again fr my specific situation. How do I add a "C" wire to my existing air ...
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7k 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 ...
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46 views

How to connect 4 fan coils with one wall control thermostat?

I have 4 fan coils (Sabiana sk-22)and I want to connect them with one wall control thermostat. How can I do?