Questions tagged [thermostat-c-wire]

The "C" or Common wire provides a way to get constant 24VAC power to the thermostat, now required by many newer thermostats with WiFi and/or touchscreens.

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43 views

Would it be dangerous to tap an existing flame sensor circuit to create a common connection for my thermostat?

I'm considering using this answer to connect a common wire to my thermostat. I have the exact same setup, and have verified with my multimiter that the red T terminal outside F terminal beeps, while ...
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Honeywell 5-wire zone valve wiring

Update: I was able to successfully re-wire a spare wire to my Google Nest Thermostat 2020 AND reconnect power to the C-Wire of my 3rd generation Nest Learning Thermostat. Turns out the 3-amp fuse in ...
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Thermostat replacement, no c wire

I have an almost 20 year old Taco thermostat that I am trying to replace with a Nest thermostat for a forced hot water heating system. The Nest requires a W, R, and common wire, current only uses W ...
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Is it possible to add a C-wire to a Honeywell R7284 Oil Primary Control (current two-wire system)?

I currently have a two-wire system (R/W) going to my thermostat. The furnace is an oil heat system with a blower to force air. There is currently a Honeywell R7284 Oil Primary Control where the ...
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65 views

Not getting power to a new C Wire

I am trying to finish installation of a new nest thermostat and ran into the dreaded “no C wire” issue. After reviewing several posts here, I felt pretty confident that with my new-ish furnace I could ...
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Where to connect common wire from thermostat to First Co. air handler?

I'm trying to install a new Honeywell WiFi 9000 thermostat which requires a common wire. When I removed my old thermostat, I can see there are two extra wires in my wall (black and orange wire) that ...
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Wiring Boiler for a C wire Adapter

I want to install a smart thermostat for one of my boiler zones. My thermostat doesn't have a C wire. It looks like installing an adapter would be the best option, but I am not sure my system is ...
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Nest and ZVC404-4

I am trying to update my thermostat to Nest. Get 4 Nest but could not get it working at all. The HVAC control board actually have C-wire (it was not used previously, I connected it when I start the ...
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Connecting C-wire to Nest Thermostat for Lennox HVAC

My Nest thermostat has been running fine for quite a while, but recently it started complaining about low battery and wi-fi gets shut down due to power issues. I've been looking for the answer, and I ...
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Adding a C Wire using a 24V AC Transformer to a 2 Wire Heating System for Nest

Continuation from Can I use any of my existing oil control terminals (TTFFAA) for a C wire? EDIT: Wanted to finally say this is SOLVED with help from @JPhi1618 (see conversation below). If you have a ...
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Can I use any of my existing oil control terminals (TTFFAA) for a C wire?

I, like many other, similar users on this site, am trying to install a WiFi-enabled thermostat. Hopefully there isn't a prize for oldest system. My current system setup is: Oil furnace (Heat only / ...
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68 views

OK to use this C-wire in old boiler for Nest smart thermostat?

I have an old heat-only gas system with radiators, the boiler is a Willaimson-Thermoflo GWA070NS. I'm trying to install a Nest thermostat but only the R and W wires were in use with my old one. There'...
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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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75 views

What Do I Lose With a Honeywell C-wire Adapter?

I'm upgrading to a smart thermostat, which requires a C wire. My current thermostat cable has 4 wires, no C wire. The controller in the furnace does have a C connection. The system has both heat and ...
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How to create a C-Wire from Honeywell R8888A/B

So Ive been trying to install a new Honeywell wi-fi thermostat. I have been unsuccessful in any event. I have a third wire unused at every thermostat in my home which is black. This black wire tuns ...
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132 views

How to connect C-Wire to Weil-McLain Boiler CGa Series 3

I'm trying to install a Nest learning WIFI thermostat to my boiler. However, I'm not sure where to connect the common wire. I've went through multiple posts on this forum but unfortunately wasn't able ...
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156 views

Can a thermostats C-wire be connected to the furnaces R-terminal without issues?

I was looking around at my furnace wiring to see if my C-wire was connected on the furnace side and noticed that the C-wire from the thermostat goes to the R-terminal on the furnace. This doesn't ...
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Another c-wire challenge

Opened the furnace to find this situation: Red and white coming in from the left are from the thermostat. Yellow wire nut is labeled C. Other end is in the circuit board. What do I connect the C-wire ...
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Smart Thermostat - Boiler does not have a C terminal. Can I use the TV or T instead

I am trying to install an Amazon smart thermostat but the boiler does not have a C terminal. It has a C1 terminal but I do not think it is the same due to it being connected to the circulator pump (I ...
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An issue with Installing C connector to the Weil McLain boiler

I'm trying to install a C connector to my Weil McLain boiler. The C connector instruction seems simple. Just connect all Ws to Ws, and Rs to Rs as the picture below. but the wiring in my boiler seems ...
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229 views

Connecting a Google Nest Power Connector to Lennox GSB8-E

Installing Nest thermostat, getting no c-wire error. Get the nest power connector, to attach to the circuit board of the boiler......and that is where I get lost. Green wire in center has 24V ...
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Fast Stat Common Maker Setup on 2 Wire Boiler

I'm trying to wire up my ecobee in a new house that only has 2 thermostat wires (R, W). I bought a Fast Stat, but I'm unsure how to set it up as I have a complicated setup. There are two aquastats (...
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Where can I connect c wire from adaptor if I don’t have c terminal in my boiler control board

I was wondering if someone can help, I have an IBC boiler (heating only) and trying to install a smart Google thermostat that requires a c wire. I also got the Google nest power adapter where you put ...
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No “c” wire terminal on my furnace

My furnace doesn’t seem to have a “c” terminal I can hook up my adapter to for the nest smart thermostat. My terminals are numbered instead of lettered. I tried them both but the thermostat still had ...
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Installing a Nest Thermostat can't find circuit board

Hello so recently I have been wanting to install one of these nest thermostats into my home and realized I didn't have a C wire and it was recommended to install a google nest power connector, the ...
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C wire possibly on my boiler/heat pump

Hey so I know this is annoying and asked way too often but the wife wants a WiFi thermostat and of course I don’t have a “c” wire hooked up and there is no “c” terminal on my control board. We have ...
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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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139 views

Nest Thermostat Wiring problem - Heat does not work

I recently replaced my old American Standard thermostat with Google Nest. Cooling works fine but Heat does not work and simply goes into an unending loop of 'delayed: will start in 2:30 secs' I think ...
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Neutral Wire on Oil Boiler

I am going to help out a friend hook up their nest thermostat and as you might have guessed it's only a 2 wire at the location of the thermostat. Since the cheaper and newer version of the Nest ...
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54 views

For Nest Thermostat, Can I use new wire from T to C?

Old Thermostat had no C connected to it but furnace has T with wires and there is an extra wire wrapped around at the furnace and at the Thermostat. Can I just attach to T terminal and C on the Nest? [...
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79 views

Google Nest C wire Blues

Can anyone help with my c wire blues with my Google Nest? I have two ACs, one for downstairs and another one for upstairs. I recently upgraded my battery operated t-stats with Nest. My old ones used ...
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Wifi Thermostat "C" Wire - Separate A/C & Heater System - Connection Conflict

My Honeywell Thermostat WiFi System via the "C" Wire was working correctly when the "C-WIRE" was hooked to the A/C Unit. I needed to change the "C" Wire to my Gas heating ...
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Adding a C wire or Google Power Connector to an old Lennox furnace

As the title suggests I am looking for advice on connecting a C wire or hooking up a Google Power Connector (I have it already) to my furnace. I have a Lennox G803, it already has a humidifier ...
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1answer
62 views

Ecobee 3 Lite Installation - No C Wire, only 3 labeled wires on Furnace board

Trying to install an Ecobee 3 Lite thermostat. The old thermostat had a W, G, R, and Y wire connected, but no C cable which is needed. However, I saw an unused red and blue wire in the wall and ...
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60 views

Adding a C wire to Lochinvar Boiler - 2 zones

I am trying to connect an ecobee which requires a C wire to my 2 zone heating system - boiler is a brand new Lonchinvar. My current thermostat only has a red and white wire (I have no AC, just heat). ...
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139 views

Please help me find the right spot to tap into for C wire at the furnace

I am trying to upgrade our thermostat to a Wifi unit that needs a C-wire. Found the unused C wire at the thermostat end and connected it. AC wouldn't power on, went to furnace end and found it wasn'...
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28V at furnace, 0V at previously working thermostat

This is a followup to an earlier question I posted where it appeared that the previously unused Common wire on my HVAC system was damaged. All of the other wires read 28V between them and R, and the ...
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149 views

Low voltage over C wire at thermostat

Similarly to this question of the same name, I am reading low voltage over the R,C wires at the thermostat. Unlike that question, however, the voltage is unusably low. I am only reading 2V over R,C ...
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Identify HW aquastat and add common wire to Honeywell aquastat

This has been asked before, but I can't find any info on my Honeywell aquastat. The model number, normally on the inside paper on inside of cover, is missing so I do not have any model number. There ...
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2answers
512 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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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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C wire not identified

I have the c wire which I removed and reinserted but still the thermostat showing error that its not identified
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72 views

Smart Thermostat with TWE040E13FB2

I have a trane TWE040E13FB2 hooked up to a heat pump. I am wanting to install a smart thermostat. Our current thermostat has 10 wires in it. I do not have a common wire. I also don't see a common wire ...
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25 views

Refrigerator Compressor not working?

I unplugged then plugged back in my fridge an it isn't cooling or freezing! Does that mean my compressor is no more working? The light comes on inside the icebox?? Just not cooling or freezing..
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Hvac/thermostat wiring questions and problems

I have a modular home. My hvac system is a heat pump/ac with emergency heat strips. It has 5 wires in the wall and my thermostat is battery operated. I want to install a new Honeywell thermostat with ...
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2answers
131 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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62 views

C wire for wifi thermostat

I'm at a loss. I have a wifi thermostat to install. No c wire connected so a 4 wire thermostat but have 4 additional wires unused. I checked our Goodman ac/furnace and found the unused blue wire. The ...
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Swap 2nd thermostat for *off* swtich downstream of 1st thermostat

I have two thermostats running two different fans wired up like this: I'd like to replace the 2nd thermostat (on the right, in box #2) with a switch. I have done this and have the ability to turn Fan ...
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69 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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199 views

Help needed on thermostat wiring with Ecobee and Fast-Stat 5000

I'm trying to replace existing Honeywell controller for my furnace with Ecobee 3. The Honeywell controller does not use a C wire, however there are a black wire and blue wire in the wall behind the ...

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