Questions tagged [thermostat]

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

282 questions with no upvoted or accepted answers
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97 views

Replacing my Honeywell thermostat with a Nest heatlink in the UK

Can someone help with this. Trying to pick the C wire and the NO wire from here. Please note I am in the UK
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How is an air handler's fan controlled if its control board doesn't have a G terminal?

Background I have a 2-stage cooling heat pump unit from Bryant, installed ~2006 (central Florida): Condenser model 698BNX048-B Handler model FE4ANB006 Shortly after moving in ~5 years ago, our evap ...
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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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293 views

Can I use this White Wire for a thermostat C wire?

An AC-only machine cools a storage facility: no heat. The 30 year old thermostat is to be replaced with a wifi thermostat, which requires a C-wire to power the electronics. There are 4 wires: Red (...
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3k views

Why my baseboard heater won’t turn with new thermostat?

I have a pair of electromod basement heater. The label on each of them show them show 750/1000W. Power supply to this is 240V I am trying to replace the old manual thermostat with a progrmabale one. ...
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2k views

Trane Weathertron Stat to Honeywell RTH2510

I have a Trane Weathertron thermostat thst I am replacing with a New Honeywell RTH2510. This is a heat pump with auxiliary electric heat. The wires on the Tran thermostat are. R, T, O, G, Y, B, X2 ...
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2answers
200 views

Adding a C wire for a Nest thermostat

I tried upgrading to a Nest thermostat, and that's how I discovered I don't have a C wire... I'm thinking how to add it. I have some interesting situation: single furnace, and 4 zones connected to it ...
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40 views

HVAC Blower Fan stays on ALL THE TIME - Even when the system is off

My HVAC Blower fan stays on even when I remove the thermostat face plate (with the fan in the auto position and the thermostat in the off position). I have tested for a short in the thermostat wire ...
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2answers
77 views

Installing c wire in older furnace

I just installed a nest thermostat and need to hookup the c wire inside the furnace. I read where you need to connect the c wire to the secondary wire on the 24v side of the transformer. There are 2 ...
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72 views

Thermostat T694B replacing with Honeywell SuitePRO TB6575A1000

I am replacing a Thermostat T694B with a Honeywell SuitePRO TB6575A1000 in an apartment building with switchover heating/cooling, so presumably two-pipe system. Button-wiring mapping: Lo: 1 Med: 2 ...
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231 views

Changing Weathertron to Honeywell Thermostat

I have a GE Weathertron (model 3AAT80 1A1/2A1) that I want to switch over to a Honeywell (RTH6360). Most of the wiring seems straight forward, but ... R (Weathertron) to R (Honeywell) O ...
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157 views

How does this wiring work?

I have a Trane XV90 and XL 14i. The wiring looks a little strange as in the picture bellow. _____________ | | BK W2 W1 R G Y B/C YLO O |___||...
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Tracing a dead thermostat wire conductor in wall

My home was rewired and remodeled in 2014 but I am finding out that the electrician did not run a new thermostat wire from my upstairs thermostat. I have a newer-looking 4-conductor wire coming out of ...
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67 views

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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2k 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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Can I calibrate this thermostat? (Cadet brand, 240V)

My thermostat operates but seems to be badly calibrated. It will hold temperature, and you can adjust that temperature, but its not the temperature it says on the dial! It goes much higher than the ...
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687 views

Honeywell RTH5160D Thermostat Wiring w/ Heat Pump

I have installed a Goodman heat pump and a Honeywell RTH5160D thermostat. I chose that thermostat because it is supposed to switch automatically between cooling and heat modes. The system has been ...
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51 views

New thermostat turns fan off when set to on, never turns off on auto

My oil heat furnace was functioning normally on an old mercury switch thermostat, but I wanted to replace it with a programmable Honeywell 5+2 one. There were Y, W, G, R, and B wires screwed in on the ...
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60 views

Thermostat wiring for ac

I recently installed a nest thermostat for our AC system. Unfortunately I was short sighted and just assumed all the wires were the color I needed. Since installing the thermostat our system won’t ...
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1answer
2k views

Furnace Connect G Wire

I have a dual energy electric/oil furnace that is wired to a thermostat with 2 wires R and W. I don't have any AC. Inside the furnace there is a switch relay to control the fan but it is not connected ...
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148 views

Will the existing wiring work with the new thermostat?

I am looking to upgrade my line voltage thermostat from a Dimplex mechanical thermostat to a Honeywell digital thermostat. Both thermostat has 2 wires on its back. Would the new thermostat work if I ...
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2k views

C-wire on Weil-McLain CGA Series 2

I have an old thermostat with only 2 wires connected to my Weil-McLain CGA Series 2 boiler. I would like to replace it with a Nest thermostat. I need to add a C-Wire in order for it to work. Luckily, ...
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1answer
584 views

Installing a Hive Thermostat

I purchased a HIVE thermostat and want some assurance before I go about installing this. First of all i was wondering where to put the receiver as I thought it would just replace one of the ...
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1k views

Honeywell WiFi thermostat jumper loop separate ac and gas furnace

I need to validate my understanding for the installation of a WiFi thermostat that requires 24volt continuous power to operate in a constant state. I am DIYer who is computer literate. Like a number ...
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2k views

Is Nest 3rd Gen Thermostat compatible as a replacement for Honeywell TH3110D1008

I have an Ultra-Zone EWC-ST-2E controller unit for my gas AC unit at home (heating and cooling). It is set for two zones. Where the first zone has to be on (heating or cooling) in order to enable to ...
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115 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 22....
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1k views

Are w1 and w2 both energized during a second stage heat call from the thermostat?

Short version: does two-stage thermostat always close W1 circuit when it closes W2 circuit, or they might be closed independently? Long version: I have two-stage furnace, currently connected to older ...
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1answer
149 views

New thermostat: How to wire it?

My old air conditioner thermostat broke down, so I bought a new one. But when it arrived, I was horrified to discover that the terminal of the wires were not named the same. Both thermostats have ...
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38 views

C Wire on Furnace bundled up to go to the thermostat, but not on Thermostat?

I just moved into a new home and wanted to install a smart Thermostat, upon checking behind my current thermostat I noticed that there was no C- Wire, so I checked the Furnace, and saw a C-Wire, which ...
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54 views

Did I blow a fuse? Wiring 7 wires to thermostat

Did I blow a fuse? I had taken pictures before I de-wired the unit. Turned off the circuit breaker (mixed up the terms its the switch boxes). The taken the whole unit off the wall, to fix the anchor ...
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22 views

Is there a way to have one thermostat control a heat pump and a 3 zone hydronic system?

I have two heating systems that are independent of each other. One is a 3 zone hydronic system with 3 thermostats controlling a pump controller. The second system is a air to air heat pump without ...
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42 views

Thermostat calling for heat but brand new Taco Zone Switch not opening?

I have a trusty old gas boiler that succeeded at providing baseboard heat to 2 zones for years. I recently had a third zone added. This is a 2-wire, heat-only system. The electrician tried and couldn'...
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18 views

Want to add a C-wire to a ClimateMaster Compact Heat Pump in combination with a Nest learning thermostat

My existing Nest learning thermostat, 3rd gen, is draining the battery really fast when use the wifi. I have a ClimateMaster Water Source Heat Pump. It has only four wires. I run an extra wire to ...
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1answer
58 views

Adding a C Wire to a wall mounted gas heater for a WiFI Thermostat

I have a typical 2 wire thermostat for a wall mounted propane heater. I want to install a wifi honeywell thermostat. The thermostat is right next to the heater so running a third wire is no problem I ...
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89 views

Can I replace this old mercury thermostat with a digital one for wood/oil furnace?

I recently moved into a house that was built around 1999, and it has an old Newmac wood/oil combo furnace that seems to be the original heating equipment. It has two separate thermostats in the ...
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48 views

Trane XV95 thermostat wiring

I have a Trane XV95 two stage furnace, wired up to a single stage thermostat. The W1 and W2 ports on the furnace are jumpered. Currently has a 4 wire cable. I'm trying to figure out if it's worth ...
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34 views

Thermotstat Wiring Confusion

I live in a condo with hot water baseboards that are connected to a shared boiler system. I currently have a simple bimetallic strip thermostat that I'd like to replace with a digital or a smart ...
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57 views

Why is the 'E' terminal connected on my thermostat?

I'm trying to update my Honeywell TH4210D1005 thermostat to a nest thermostat. On researching the Honeywell thermostat, it seems to be designed for systems with heat pumps? Further, it does have the E ...
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44 views

Options for smart thermostats with a 2 wire gangbox

I have baseboard heaters, and am interested in getting a smart thermostat like the Mysa. My existing thermostats are 2 Ouellet OTH600s (similar to this) and one Honeywell Linevoltpro. These control my ...
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231 views

Hive Wiring Advice - Combi Boiler

I've just moved house and am trying to wire up the hive (as I did in my previous house with no problems). I have a combi boiler (Ideal Logic 30) and a single-channel hive receiver. The old thermostat (...
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30 views

Trying to wire a nest thermostat E in UK with 2 live wire and 2 neutrals

I live in the UK and am trying to replace a Honeywell WiFi thermostat with a Google Nest thermostat E. I have 2 3-core wires coming into my thermostat, 2 live and 2 neutral wires, 1 pair I believe are ...
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72 views

For a smart thermostat, where do I attach the C wire to my furnace?

I know I've seen several questions out there about getting a C wire for a smart thermostat, however after all the research I've done and people who have given me guidance so far I have still had no ...
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2answers
101 views

Hooking up AC compressor to an old Lennox furnace

I'm trying to connect an ac compressor to an old Lennox G12Q3-110-3 furnace. Tried it a couple of ways and can either get the compressor to turn on or the furnace fan. Not both. Any ideas on how to ...
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50 views

Nest Thermostat wiring for heat pump

I am trying to replace my Honeywell Thermostat that is connected to a Honeywell EIM with a Nest Thermostat. I only have a 4 wire (G,B,R and W) ran from the EIM to the thermostat. My understanding is I ...
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2answers
67 views

I need a C wire connection for my new Glas thermostat

I have 3 wires(red,white,and green) going to my thermostat. I’m replacing my old thermostat with a new one the requires a C wire connection. The 3 wires goes to my Honeywell aquastat. The white goes ...
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34 views

Confused about HVAC wires

My townhome is using a heat pump and it's currently connected to a honeywell 3000 thermostat. I bought a gen 3 nest and from what I can tell, it's compatible. However, I'm a bit confused about my ...
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39 views

No Power to Thermostats - Even after Replacing

I changed my thermostats from Honeywell Smart TH6220wf2006/u Lyric T6 Pro WiFi to Honeywell T5 Programmable (NOT Smart) and couldn't get my furnace to push air out, but AC worked fine. A friend was ...
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46 views

Honeywell RTH9585WF thermostat behavior with heat pump and Emergency heat

I just installed a Honeywell RTH9585WF1012 to control my forced air furnace system which has: Cool: 1-stage heat pump Heat: 1-stage heat pump (same) + emergency gaz heat from furnace I have a fossil ...
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63 views

Is this blue wire in my A/C a C wire I can use at the thermostat?

Here's my current setup - separate A/C and boiler units. Some of the pictures may be confusing because the wires are differently colored than they're named, but I'm going by my actual thermostat. ...
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182 views

Connecting fresh-air damper to Lennox furnace OR replacing timer with new smart thermostat

We replaced a 20-year-old furnace with a new Lennox furnace and added air conditioning. The new system is still controlled by the 20-year-old Honeywell Chronotherm III thermostat. The furnace had (and ...

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