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

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Is the Nest thermostat smart enough to turn itself on BEFORE you get home?

I'm wondering if in "Away" mode, is Nest smart enough to learn about when you come home, and kick on approximately 30-40 minutes BEFORE then? Or does it only kick on when it senses you've come home? ...
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2answers
1k views

thermostat batteries replaced, AC unit won't start

Came home from work to find no AC. I checked the thermostat and the display was blank. After replacing the batteries and resetting the program, my AC unit never started up. I checked: - The AC unit ...
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1answer
277 views

Replacement thermostat wiring

I have an American Standard heat pump AC. I'm replacing a White-Rodgers manual thermostat (where I move a switch from cold to heat) with a Honeywell RTH7600 (which will automatically switch from cold ...
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3answers
19k views

Adding a C wire to a new Honeywell WIfi Thermostat

I am trying to install a new Honeywell touchscreen WIFI thermostat and need to add a C wire to my terminal inside the furnace (using the help found at How can I add a "C" wire to my ...
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2answers
964 views

Wifi Thermostat wiring

Replacing 2 Hunter thermostats with a Honeywell RTH9580 Wifi. Neither unit has a C wire - I'm comfortable with the upstairs high efficiency unit, but the downstairs older unit has thrown me for a ...
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1answer
885 views

Need to add common “C” for thermostat; can anyone indicate where to connect it?

We just got a new WiFi capable thermostat that, unfortunately, seems to use a form of power stealing in order to charge itself. The problem here is that our house is actually quite well insulated; the ...
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2answers
548 views

Thermostat / Oil Furnace Question

I have an old oil furnace and I am looking for some clarification as to how it is supposed to work. It heats water filled radiators through out the house. Currently it is connected to a thermostat ...
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2answers
4k views

Which terminal should I connect it to for a “C” wire when none are labeled “C”? [duplicate]

I am looking to replace my old battery operated thermostat with a new wifi model. There is no "C" common wire connected to my old thermostat. There is a blue wire that is at the thermostat but cut ...
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1answer
913 views

How to wire a new Honeywell RTF6580WF thermostat to replace a Chronotherm IV?

I have an old Honeywell Chronotherm IV thermostat that I am trying to replace with a Honeywell RTF6580WF wifi thermostat. I have a gas furnace and an air conditioner. Wiring for Chronotherm IV ...
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1answer
1k views

How do I wire this thermostat?

Hello I have a Honeywell FocusPRO 5000 Non-Programmable 1 Heat/1 Cool Thermostat, Large Screen. The wires it needs are: Conventional Terminals: Rc 24VAC power from cooling transformer R ...
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1answer
445 views

thermostat c wire question [duplicate]

I am looking to install a new thermostat that will require a C wire. I have a single stage A/C unit and my current thermostat has Rc, G, and Y wires. There is also an unused blue wire which I traced ...
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1answer
852 views

Why isn't my thermostat clicking on/off automatically?

My thermostat is not clicking on/off automatically, I have called my landlord and they replaced a very old one with a brand new one and it is still not clicking on off automatically, but will ...
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1answer
726 views

Which wall should I install a replacement thermostat on?

I'm replacing an old thermostat that is behind a door to our dining room, that is usually kept open, hiding the thermostat. Given that the wires come from above and I have some flexibility as to ...
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1answer
807 views

How to balance thermostat settings between zones to maximize efficiency?

I recently purchased a house so this is my first winter in it. The house was built in 1939 so most of the house is on a single heating zone using hot water radiated heat. The radiators are cast iron ...
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2answers
2k views

How do I diagnose a thermostat and HVAC that intermittently doesn't respond?

My gas heater for the whole house does not follow the thermostat settings on some mornings. I have set it to 70 degrees at 6 am but now it is still 60 at 8 am. This happens weekly once or so and seems ...
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2answers
488 views

Is there a thermostat-controlled corn heater sized for a shop/garage?

I'm looking for a way to heat my 4-car garage. Two bays are for cars, one is for the mower and other items, one is my workshop. I live in Minnesota, with very cold winters, so a heater is necessary ...
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2answers
17k views

Why won't my heater turn off when it reaches my desired temperature?

My wife and I purchased our first home this past year and we did a bunch of repairs up-front via a rehab loan, and one of the things we replaced was a very old thermostat with a new digital one. I ...
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1answer
14 views

Can't get fan working on thermostat

I recently purchased a new thermostat. My old thermostat worked for heat (no AC either) but the fan wouldn't go on when I turned to "On" (in hopes to move some cool air from the basement up during the ...
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0answers
27 views

Should I install a doorway fan or dehumidifier?

I have central air in a rancher (one floor), and the living room is on one end of the house. That room is on a slab, and has always been noticeably hotter in the summer and colder in the winter than ...
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1answer
60 views

How to override an attic thermostat with a wall switch?

I want to install a fan in my attic. I want the fan to be controlled by a thermostat in the attic, but I want the ability to bypass or override the fan from within my house. Ideally I would like to ...
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2answers
58 views

Why “W” (heat contactor) and “E” Aux Heat connected in Thermostat

I'm trying to update my thermostat to one that has a scheduling feature. My plan is to just copy how it was hooked up in an old 129N Thermostat from Armstrong however, I can't figure out why the "W" ...
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0answers
35 views

How to Change Chinese HVAC Thermostat

I am looking to put Nest thermostats in the house, I have now found out my entire house (one in each room, 6 of them) has been wired with HVAC Chinese U12A UNIVERSAL A/C CONTROL SYSTEM urrgh – they ...
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1answer
140 views

Why does adding a C wire for a thermostat blow the fuse?

I am adding a WiFi thermostat. I have R,W,G,Y wires. Plus 2 extra coming from upstairs that go between humidifier and humidistat. So I ran an extra wire for the C wire. When I attach it to the C ...
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1answer
304 views

Adding a C/Common wire to HVAC system

So I'm looking for some help in identifying where I can attach a C/Common Wire to my HVAC system, but unfortunately my system doesn't have a control board that I can easily attach a powerkit to. For ...
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1answer
139 views

Wiring new 'c' wire to heat pump system. Do I need to connect at both air handler and condenser?

I am planning on installing a new WIFI thermostat (Honeywell RTH6580WF). I have a heat pump system (outdoor condenser unit and air handler in attic). Old thermostat did not have a 'c' wire, but it ...
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0answers
21 views

How to replace a line voltage thermostat with a low voltage one? [duplicate]

I have one of those round mechanical knob thermostats (line voltage). I would like to replace it with a wireless thermostat which is controllable from an Android phone. It seems those thermostats are ...
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0answers
35 views

Replaced Thermostat, Furnace worked for 1 cycle now blows cold

Hello I just replaced my old White-Rodgers thermostat because it just wasn't working consistently (sometimes it would turn on the furnace, but mostly it wouldn't). I swapped it with a White-Rodgers ...
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0answers
23 views

Why would one of the zones of my Slant Fin gas fired hot water baseboard heating system not be heating?

Thus far I have: replaced with new batteries. turned down temp and switched the breakers turned heat back up, no response Can a pilot be out for one zone? The other two are warm and cozy. Did ...
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0answers
187 views

Can't find the circuit board of my HVAC system

I'm trying to install a wireless thermostat for my church building's HVAC system. Currently there is no C wire, so I tried to see where the circuit board was so I could install one. I couldn't find ...
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0answers
42 views

How do I wire a Honeywell ultrastat TB7220U for second stage cooling?

Has anyone wired this commercial thermostat in before? Honeywell TB7220U ultrastat I had needed to know about the 2nd stage cool wiring set up -y2? And changing the wiring correctly for install ...
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0answers
255 views

How can I tell if C wire is active and connected to Thermostats?

We are trying to install a smart thermostat (Ecobee 3) so we are in need of a C wire from our boiler. We see a green wire in the wall, but it's not connected to our thermostat currently since it ...
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34 views

Why are certain radiators hot during the night when the thermostat is very low?

We have a gas central heating system and we have set the thermostat to come on at different temperatures during the day. Generally between 7.00 and 22.00 it is set between 19 to 22 centigrade. From ...
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417 views

Can I use the T terminal in my furnace as the C for a Wifi Thermostat?

I've read many posts on this, and believe I know what to do, but want to make sure. My furnace (a Lennox G14 Series) does not have a C terminal which needs to be connected to the C terminal in my new ...
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1answer
55 views

Updating thermostats to single system

I have a three floors in my house, each controlled by it's own thermostat (separate air handlers and mechanical valves on furnace). Baseboard heat. The three thermostats are controlled separately, ...
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1answer
617 views

Where can I connect the C wire on the A/C side?

I’m trying to replace my thermostat with the Honeywell Smart-WiFi thermostat. Quick summary, I have an extra yellow wire which I’m making the C wire, but its not connected at the other end and I’m not ...
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1answer
184 views

Zoned oil furnace and AC thermostat question

I recently moved into a new home and wanted to replace the old thermostats with digital Honeywell ones. From what I understand the home has a Rheem 10 Seer (1996) compressor and a Williams oil furnace ...
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1answer
292 views

Using a second thermostat to balance temperatures thru fan-only control

Like many others, temperatures between the two levels of my house are uneven. This is particularly noticeable as spring arrives and the upper floor (above ground) enjoys solar heating (so the heater ...
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0answers
122 views

Why won't a NEST that shares control of a furnace with a conventional thermostat turn on the heat?

I have three floors in my home. The bottom floor has its own gas furnace and the 2nd and 3rd floors share another gas furnace. Everything was working great until I added a NEST to the first and ...
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1answer
608 views

How do I connect a C-wire on a Triangle Tube Prestige Solo 110? [duplicate]

I purchased a Honeywell RTH6580WF to use with my recently installed Triangle Tube Prestige Solo 110 propane boiler. I only have two wires at my existing heat-only thermostat. I understand that the ...
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0answers
93 views

Why doesn't my A/C get power when using the alternate C-wire thermostat hook-up method?

I changed my old Honeywell thermostat for a new Honeywell WiFi thermostat. I installed it just as the directions stated. I used the alternate C-wire method as the old unit did not have one. ...
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0answers
56 views

How can I add a common “C” wire to my thermostat? [duplicate]

Possible Duplicate: Options for adding “C” wire to thermostat I recently bought the Honeywell THM5320R Wireless thermostat. After going to hook it up I found what many others have, it ...
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3answers
52k views

Why won't my A/C turn on after I replaced the thermostat batteries?

Our thermostat died yesterday, but after replacing the dead batteries with fresh batteries, and confirming the LCD screen was operable, our AC no longer turns on. I have attempted a factory reset on ...
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1answer
296 views

How can I consolidate different heating/cooling systems into a single system?

I have 3 different types of heating/cooling systems that I inherited. Hot water heat. This heats the whole house/garage via 3 zones. Zone 1: Kitchen/Livingroom Zone 2: Bedrooms/Bath Zone 3: Garage ...
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1answer
2k views

How to connect Nest in Europe

I found a question regarding the Nest thermostat here. But that is only a question "Will it work?". Thanks to that I know it WILL, the problem is...HOW. I know the wire naming conventions are ...
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1answer
546 views

How can I install a nest thermostat with no wires?

I have zoned heating/AC/heat pump. My original thermostat on the wall is NOT connected to any wires, in other words it is wireless. I thought it had wires so bought the new Nest thermostat. ...
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1answer
303 views

air conditioning system stays on even when we turn off our thermostat

Our A/C system stays on even when we turn off our thermostat. What should we do to try to fix it?
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2answers
109 views

Temperature control when I can't affect either airflow or thermostat

Our apartment is heated by a natural gas burner (the burner itself is inside the unit) that vents in two directions: one vent into the bedroom and a second (about 3x the area) into the rest of the ...
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1answer
68 views

AC continues to run for several minutes after shutting off

When I turn off the AC it continues to blow cold air for several minutes. I realize this may be an energy savings feature, but I'd like to know if it is possible to disable it. In other words, what ...
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2answers
717 views

Where to attach the “C” wire to my furnace?

I am upgrading to a new thermostat which requires a "c" wire to power it. I have an unused blue wire running from my thermostat to my furnace that I plan to use as the common wire. However, I am ...
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2answers
42 views

thermostats for high desert climate

We live in Spokane, WA, a high-desert climate. We don't need a programmable thermostat, but we do need one to keep an constant ambient temperature range. This may mean A/C during the day, and heat at ...