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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5k views

Need help wiring a new double pole line voltage thermostat

[ Just bought my first home and this is my first time posting, so please forgive me if my terminology is incorrect. I currently have bedrooms upstairs each with 1 baseboard heater and thermostat for ...
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43 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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1answer
80 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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22 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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81 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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1answer
43 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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2answers
274 views

Nest E Thermostat Power

My thermostat is in the basement, connected to a Honeywell R845A to run a circulating pump for heat. I bought an Nest E for the main house and it works great. I want to replace the thermostat in the ...
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1answer
49 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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34 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
1k views

Honeywell thermostat oozing yellow and programing not working

I installed a Honeywell thermostat last year for our boiler and it worked perfectly. This year we were having issues with it not following the program schedule. The thermostat should be sleeping and ...
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1answer
50 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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44 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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59 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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5answers
4k views

Is there a filter-reminder thermostat that uses run-time instead of total time?

My HVAC filter is in my crawlspace and is a hassle to change. I don't want to change it more than needed. "Change it every month" is bogus advice because in some months (like May) we don't have to run ...
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43 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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5answers
12k views

Should I replace my mercury switch thermostat?

We have an old mercury switch thermostat in our house, You know the type, gold ring, very common. We are in new England on a gas/steam system. There is no central AC. We have been told by more than ...
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197 views

Lennox G16Q3-50 Furnace with AC, Door Interlock Switch and Main Circuit Breaker

If the door of the Lennox G16 is removed, thus the door interlock switch unpressed and system off. Does this mean that I only need to shut off the AC power from the outside breaker panel and leave the ...
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1answer
223 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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2answers
2k views

Pulling wire using previous wire?

I’m trying to pull a new thermostat wire down from a first floor room down into the basement. The exit point in the basement is in the ceiling, between two ceiling boards pretty inaccessible. Would it ...
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3answers
729 views

The blower on my HVAC runs sometimes when it should be off

The blower on my HVAC runs sometimes when it should be off. It does not run all of the time. The furnace is in the attic and the abnormal running seems to be related to the attic temperature. ...
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2answers
95 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
29 views

re-wiring/retro-wiring a Carrier 40MVC024 ductless A/C for external thermostat: guidance

My server room has two air-conditioning units, with acutely counterproductive controls. I want to rewire them for external thermostats. Can I simply splice a traditional thermostat inline with the "...
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1answer
40 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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108 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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1answer
1k views

How do I install a WiFi thermostat with a Well-McLain steam boiler?

I have a Weil-Mclain 150000 BTU steam boiler, and have only 2 wires connected to my thermostat, but would like to add a new Honeywell WiFi thermostat. I have no C wire, no A/C, or any other type of ...
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1answer
182 views

Wiring Baystat240a to Honeywell RTH2510 w/ picture

I tried to hook up the wires but all the lettered terminals on my old thermostat don't match the letters on the Honeywell thermostat. I have the AC working but I still have three wires left over. I'm ...
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2answers
2k views

“C” wire in wall! Where does it go in air handler/furnace?

Got a wifi thermostat. Behind the old thermostat was a blue "C" wire. The other side of the blue wire in the equipment room isn't plugged into anything. I need to get the 24v common hooked up to this ...
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1answer
80 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 ...
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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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4answers
4k views

G to C trick not working for cooling. Honeywell RTH9080WF

My electric furnace has no c terminal. Furnace is heat & cool both. (Lennox Electric Fan coil Model CBS18-21-3P). I installed Honeywell RTH9080WF. I switched G to C on my thermostat and got the ...
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1answer
193 views

Where is the C wire terminal on my boiler

I am trying to connect the T5+ smart thermostat to my oil based furnace. I see there are only two used wires at the thermostat R And W but 3 additional cores available. My boiler is a old Weil McLain ...
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0answers
22 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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2answers
2k views

Electric baseboard heaters stuck on with digital thermostat

I have two electric baseboard heaters in my house that are both controlled by a single digital programmable thermostat (King ESP-230). I believe each heater is 1500w so 3000w total. Twice now in the ...
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3answers
2k views

How do I connect a C wire to an Utica PEG112CDE steam boiler?

I want to upgrade my old mercury thermostat that I currently have to a newer programmable thermostat. This little DIY project is for my first late 1920's home that I recently purchased. I currently ...
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1answer
585 views

Is it possible to add a “C” wire to my electric heater?

I bought a Wifi Thermostat but my old thermostat did not have a Common Wire. I can't use any of the swapping the G for the C solutions because I have an electric heater. I was told by Honeywell that I ...
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0answers
294 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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3answers
294 views

Making sure old Honeywell Thermostat (round dial) doesn't turn on

I've had to cover my baseboard heater with painter's tape and duct tape because I keep getting click beetles strolling into my apartment after 6pm (I live in Michigan, and the temps are dropping). I ...
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1answer
3k views

Furnace reaches temp, shuts off but wont come back on

I have an American Standard furnace (natural gas)with a manufacture date of 2004. The thing won't come on unless I power it off (have a switch right beside it that serves this purpose), let the fan ...
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393 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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0answers
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
45 views

Upgrading from a two wire analog tstat to a Nest, need help

I am looking to upgrade from an old analog tstat to a Nest. My old stat had only two wires connected (R and W) but the wire bundle had three. So I tried connecting the green wire to C and then turned ...
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1answer
90 views

how to get 240V to 4 wire 240V thermostat

I have a 2 pole circuit breaker in the panel with a 2/12 cable connected to it. Black wire is connected to one pole, white wire is connected to other pole and bare wire is connected to ground bar. ...
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3answers
560 views

Wiring for ecobee3 lite

I recently purchased the ecobee3 lite and am now stuck trying to install them. I have 3 Honeywell thermostats I am looking to replace and my heating system is oil/hot water. My home was built in 1970 ...
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2answers
254 views

Checking voltmeter on my Honeywell Wifi Programmable Thermostat

I have a wifi programmable Honeywell thermostat. Worked fine for 3 years, this morning I turned on my gas furnace for the first time this year and it would not go off, even when I set the "Heat" / "...
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2answers
945 views

How can I replace an old dial thermostat on an oil furnace with Hydrostat 3250 Plus?

I recently bought a home with an oil fired Biasi furnace that has a Hydrostat 3250-Plus attached. It uses an old analog round dial thermostat, and I'd like to replace it with a new digital (wifi) ...
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1answer
66 views

replacing old line voltage thermostat

My old 4 wire 240V mechanical line voltage thermostat stopped working. I want to replace it with a digital thermostat. Problem is I don't know the amp rating of the old thermostat. I checked with ...
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1answer
2k views

How do you remove a Carrier / Bryant Infinity thermostat control from the wall?

I have a Carrier Infinity system with model # SYSTXCCUID01-V thermostat/control. I need to temporarily remove it from the wall. I found a diagram of how to install it: (diagram source) I do not ...
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2answers
260 views

How to hook up new 5 wire HVAC cable to newer HVAC unit with only 2 wires coming from it?? WITH PHOTOS

I have a newer HVAC unit that was installed using only 2 wires to control the heating only on the unit. The unit is capable of having AC connected and I would like to wire it so that it will work with ...
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26 views

Troubleshooting remote AC (heat pump)

BACKGROUND The system was working well in July: 6AM: AC turns on and reaches target temperature of 77 deg ISSUES Although it is a heatpump in cooling mode, I will refer to the system as an AC for ...
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1answer
716 views

Turning off Power to Thermostat to Replace It

I'm replacing my old thermostat due to issues with it somehow not staying at my set temperature. It's a Simple Comfort 2001, and I'm replacing it with a newer model, a Simple Clean 2001L. Both of them ...