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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86 views

Nest Thermostat says “delayed” and never turns AC on

New Nest, replacing an old thermostat. Image of old setup: Nest setup: The Nest says "cooling" with the blue screen for about 1 second, then switches to "delayed", then just ...
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Honeywell T6360 stopped working

When decorating I opened the thermostat cover to unscrew it from the wall. I never touched any wiring, decorated, screwed it back, closed cover, done! Now the thermostat won't work. Any ideas why this ...
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Trane VX99 furnace fan to run

I would like to have the fan turn on and blow non-a/c. I only see 2 wires coming from the thermostat. In
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how to add c wire to heat pump ac unit (only have wires with nuts)

I can’t figure out which is the C wire or how to make a C wire and how to connect it to my ecobee 3lite Power extender kit. My old thermostat has wires G,Y,RH, W/E, and O/B plugged in. No "C"...
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HVAC is heating when thermostat is off

I seem to have a problem with my thermostat. I have tested the wiring of my HVAC system by wire nutting the the power (R, red wire) to the AC (Y, black wire), heat (W, white wire), and fan (G, green ...
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Thermostat shows fan running but it is not [closed]

thermostat show fan running but it is not. Tried auto and on neither works. Calling for cooling but no compressor. Reset all brea
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Is this wiring dangerous? Smart Thermostat C-wire AC adapter twisted together

Is this wiring scenario dangerous? Is it likely produce sparks or damage my HVAC system? Please read the description and see the image below. Description I didn't have a C-wire for my Emerson Sensi ...
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21 views

Honeywell C wire on a dual transformer system

Currently I have dual transformer system From heat >> RH & W1 From cool >> Y1, Rc, G Honeywell provides a C wire adapter and also mentioned turning an unused wire into a C-wire. I do ...
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44 views

Can an SPST switch be used instead of a thermostat for a gas stove?

We have a gas stove that can be either on or off. It has two wires going to a thermostat that has more capability than the stove, such as control of non-existent air conditioning and fan. The wires ...
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Where to connect C wire if no C terminal

Hi wanting to connect Nest and want to install a C wire. HVAC only appears to have G,W,R so not sure where to connect C.
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Connect separate Heat / AC systems to a Nest E

I have oil/hydro zoned heat, and a separate AC system. I have Honeywell ProSeries thermostats that have some 16 wire connectors (apparently designed to handle a nuclear power plant or something). I ...
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My thermostat will not start my air conditioner

I remember the same thing last summer where occasionally it would take a number of hours for the ac to kick on after I switched to cool and the temperature was above the threshold. The funny thing is ...
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Heater does not start without a power reset

I have a Bonaire MB3-20I and it won't turn on unless I go in the roof and turn the socket off and then on again. When this is done, it stays on for as long as needed, but when we turn the heating off ...
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Wiring for 2-stage thermostat and 2-stage furnace with single stage cooling

I got my furnace and A/C unit replaced last summer. The new furnace has 2-stage heating, the A/C unit is single stage. The installers put in a single stage thermostat, so as far as I could tell it was ...
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Programmable Thermostat wiring Question

Existing thermostat is a Honeywell and has a separate connections for Aux (white wire) and E (Emergency black wire) The proposed Honeywell T'stat only has a single terminal labeled "Aux E". ...
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Can someone assess my original thermostat's wiring setup?

This is a new world for me, I haven't messed with circuits since physics 101. When I watched a quick youtube tutorial on setting up my Nest E, I thought it'd be a simple "move wire in old C, to new C ...
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Thermostat not getting power and won't turn on fan or AC. Does have power with batteries, still no cooling

So first things first, I live in a condo. I don't have a lot of easy access to my AC (and I would imagine my furnace? I'm only guessing where that is though it might be near the water heater instead). ...
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1answer
45 views

Replacing old 3-wire line voltage single-pole thermostat with a 2-wire one

I'm trying to replace an old Mears M21 SP thermostat controlling the baseboard heater with a new one (Honeywell RLV3120A to be specific). Problem is, the old thermostat has 3 wires (Black, Red, and ...
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Rewiring for Nest Thermostat - Current ABCD Configuration Carrier

So I would like to use a Nest thermostat on my carrier system. I have the ABCD wiring configuration from current thermostat to the board on the furnace. On the attached image, you'll see three brown ...
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59 views

Thermostat not getting power (Nest E74)

I replaced an old Honeywell thermostat about a month ago with a Nest thermostat. Friday Nest started displaying an E74 error. I have two furnaces and two outdoor units, one for upstairs and for ...
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27 views

central heating comes on at night

we have had this problem for over a year on & off, we have an ideal logic+ 30w combi boiler 8 years old, in fairness has been great , but the central heating sometimes comes on in the night (full ...
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69 views

Can I Effectively Jump my Furnace Wiring for A Long Time Safely

So I live in an rental with a forced air furnace. The thermostat that controls it is an old honey well that uses ancient analog components. It works well during the winter for heating, but ...
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Upstairs is getting frigid at night during cool nights

I have a dual zone Lennox system, and it cools well, but for the past few weeks it seems to run away at random cooling the upstairs to several degrees lower than requested. We have EcoBee thermostats ...
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49 views

Thermostat replacement wiring standard

Here is my current thermostat with its wiring exposed. I have never worked with thermostats and have no idea which standards and types are present. I have searched for this scheme of wiring but ...
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2answers
42 views

Help connecting unused C wire for Smart Thermostat

Looking to connect a newer WiFi thermostat which requires the connection of a c wire. My old thermostat didn’t use a c wire however there is a c wire present in the bundle of wires ( unconnected at ...
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50 views

C Wire doesn’t work

Trying to swap an old Honeywell thermostat for new with Wi-Fi. Old thermostat doesn’t need C wire, but I have an unused blue wire in the wall. I installed the new thermostat correctly with the C wire, ...
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32 views

Are 8-Zone Wiring Centers Compatible With Smart Thermostats?

I'm looking at various wiring centers for gas boiler heating and I'm wondering if they're compatible with the major smart thermostats, such as Nest, Hive, and Honeywell. Wiring Centers: Reliance:...
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37 views

Why does my furnace have a yellow termainal?

I don't have the manual for my furnace, and the terminals are labeled C W R G and Y. The internet generally refers to Y as Cooling or Compressor. So what does Y do on my furnace?
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1answer
31 views

Old Rheem rhqa 1000 to thermostat wiring help

I cannot figure out how to wire my 30+ year old AC to my lux dmh110a thermostat, I do not have the old thermostat to reference. It seems to be 4 wires coming out of the air handler and to the ...
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58 views

Can someone please explain this gas water heater thermostat marking

What I don't understand is the box with a slash through it located counter clockwise from the larger solid bar. I'm sure it is less warm than the large box, but does it have a special meaning? I ...
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39 views

Connect “C” wire on boiler model number 1135-601

I've read several threads here and on the other websites but still can't figure out how to add C wire to my boiler wiring. I would like to replace my old mercury thermostat with Nest E or any other ...
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1answer
36 views

replacing toggle switch on furnace red-green with thermostat

currently my furnace is connected to a two wire red-white thermostat. the furnace has comon, red, green, white, and yellow terminals. red and green are connected to a toggle switch on the side of the ...
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How to wire this old Lennox thermostat to my Heil 2003 furnace?

Here is my attempt which isn't working. Maybe I should jumper R to G and move the green wire to C with Blue? The wires I cut off it had that jumpered. Here is the image address: https://imgur.com/...
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furnace thermostat problem

Thermostat is reading crazy high temps when it is really 67. Furnace won't deliver heat. Fan works. Is it the thermostat (batteries replaced already) or the furnace?
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Honeywell Home Thermostat - wiring issues?

I have the Honeywell Home - 7-Day Programmable Thermostat. When my roommate installed the device it was winter and everything appeared to work fine. Now that it’s heating up, it’s impossible to cool ...
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160 views

Why is Thermostat Y wire connected to C terminal on furnace?

I have a Nest E thermostat, and like many others have lost wifi and getting low battery because I have no common wire connected. After looking at my old Lennnox 78ugf3-75-1 furnace, I noticed that my ...
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Trouble with identifying wiring for heat pump setting up Nest

The home I moved into has a Honeywell thermostat controlling an Amana heat pump. I am trying to replace this with a Nest thermostat instead. Here is a photo of the wiring for the existing thermostat ...
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1answer
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Question About Wiring - Hooking up New Thermostat

Replacing this: src With this Honeywell Mable thermostat. Regarding the wiring, it doesn't exactly match up, can someone help clarify how to wire the the thermostat? The old wires are hooked up ...
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68 views

wiring hrv in a confusing house

some beautiful pictures first time posting apologies if my placement is off Buying HRV. I am debating between two units, venmar evo5-700 which doesn’t support furnace interlock or lifebreath rnc205, ...
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34 views

Can’t shut off power to heat-only (hydronic baseboard) thermostat

I have no AC in my condo, only hydronic baseboard heat, currently controlled by an old mercury thermostat. I have a new smart thermostat with a c-wire adapter I want to replace it. Trouble is, I’ve ...
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29 views

No Y wire to thermostat

I am trying to install a Honeywell rth6580wf thermostat. I have located all the wires except Y. It is a gas powered heat and central AC system. At the system there is a Y wire going outside to unit, ...
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Replace existing swamp cooler thermostat with smart thermostat - any special differences between the two thermostat types in this application? [duplicate]

Has anyone replaced their swamp / evaporative cooler's existing thermostat with a smart WiFi-connected thermostat like Nest or Ecobee? I want to know if there are any differences in connection or ...
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4answers
70 views

Thermostatic control of an unmanaged energy source to supply hot water cylinder

I have a solid wood burner that contains a heat exchanger. There is no guarantee that the combustion can be regulated. This heat exchanger feeds a loop that acts as the source heat exchanger in a hot ...
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52 views

replace fireplace switch with nest thermostat

I have a fireplace wired up to a switch (simple off/on), and I want to throw a Nest thermostat on there. It has a black and white wire coming out of the wall. I think the white goes to the W1 and ...
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1answer
55 views

Unconventional thermostat wire labels on boiler

I have inherited an electric boiler for heating water in pipes running through the house. The existing thermostat is a very old and very simple mechanical one. I want to install a more recent ...
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1answer
74 views

How do I wire a/c if furnace wiring compartment has no y terminal?

I have been trying to figure this out for more than a year. All was running until HVAC company came to replace 2 thermostats with nest and rewired 2 HVAC units (a front of house and a back of house ...
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78 views

Nest thermostat e heat link replacing the old danfoss

I really need help with replacing this current danfoss thermostat with a new nest thermostat e heat hub. I'm in the UK. Below is the new heatlink just need to know what wires I need to wire and what ...
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1answer
57 views

Checking my understanding - How to add C-wires for smart thermostat install x3

I'm in the process of installing some smart thermostats (Nest Thermostat E) to replace my old ones. I have a boiler radiator heating system with three zones. Two zones are straightforward heat only (...
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54 views

Replacing A Trane thermostat with A Honeywell Wifi thermostat?

Heres what I have. On A Trane brand thermostat Red wire = R Black wire = W2 White wire = W1 yellow wire = Y Green wire = G Orange wire = O Blue wire = B or from what i'm told is my C wire?? And i'm ...
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34 views

Intermittent Furnace Issue

So I have been having a bit of an issue with my furnace since installing the nest thermostat. The first day after I installed it was perfect. Everything was working. The second day I kept getting the ...

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