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.

110 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
3
votes
0answers
45 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 [![enter image description here][1]][1] [1]: https://i.stack.imgur.com/EPkJh.jpg![enter ...
3
votes
0answers
196 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 (...
2
votes
0answers
117 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 |___||...
2
votes
0answers
102 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 ...
2
votes
0answers
230 views

C-Wire for a Vulcan Gas Central Heater for Nest Thermostat-E

I'm hoping the friendly people here could help me. I'm looking to purchase a Nest Thermostat-E but my current thermostat (Vulcan/Bonaire Summer Breeze) only has 2 black wires connected. I've searched ...
2
votes
1answer
88 views

Can I pull a c-wire from a second nearby thermostat?

I have a thermostat that controls the AC/Heat upstairs which is located on my bedroom wall. Right below that I have another Millivolt thermostat for the gas fireplace in my bedroom. If I want to ...
2
votes
0answers
1k 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, ...
2
votes
2answers
336 views

Lennox G23Q3/4-100-2 And Ecobee4

**Pictures attached to go along with my rambling explanation I have my Lennox G23Q3/4-100-2 natural gas furnace and my central air system that has been working since 1995 on a basic programmable ...
2
votes
0answers
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 ...
2
votes
0answers
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 ...
2
votes
0answers
2k views

Where to connect the c wire for a gas HW boiler (heat only) w/Wi-Fi Thermostat

I recently purchased a new Thermostat with Wi-Fi capabilites for use in one zone of a two zone baseboard hot water heating system. I pulled the existing thermostat (stat) to look at the wiring and ...
1
vote
0answers
48 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. ...
1
vote
0answers
56 views

C Wire - Williamson Furnace/Honeywell Thermostat

I'm trying to install a new wifi thermostat, but am a little confused. I have 5 wires, but none are connected to the C in the thermostat, as seen below: Additionally, when I trace the thermostat to ...
1
vote
2answers
43 views

Adding the c wire to a two wire system

I purchased a RTH9585WF smart color thermostat to replace my mercury controlled thermostat. How do I add the blue common wire at the boiler relay where the two wire system is connected? ://i.stack....
1
vote
0answers
133 views

Burning smell from AC vents after installing new thermostat

I was installing a new thermostat (ecobee3 lite Smart Thermostat, 2nd gen) to my AC unit (ARUF61D14AA). I opened my current thermostat and noticed that I don't have a C-wire (which is required for the ...
1
vote
0answers
113 views

help me find C wire on williamson boiler and where should I connect it

I have Williamson boiler GWA 140,000 BTU. I have 2 zones in my house for heating. On one zone I want to install smart thermostat so, I need C wire. The old thermostat for this zone had 2 wires: red ...
1
vote
1answer
55 views

Where do I connect my new T-Stat in my Weil Mclain boiler

I have a new smart thermostat and looking to connect to my boiler. As you can see in the picture there are (2) yellow wires which are labeled 24v control. One yellow wire is connected to the Y ...
1
vote
0answers
92 views

Problems w/ Nest

I've got a common problem but I can't seem to find the simple answer. My heating system is simple. Forced water oil boiler with three zones. Two zones are controlled by the Nest E Thermostat. I'm ...
1
vote
0answers
34 views

How can I install a smart thermostat with my HVAC system?

I have a Ruud furnace / air handler with a non-programmable thermostat installed. It looks to be a model RGPE-07EBRQR (Rheem?). I want to put in an Ecobee and am a bit confused about the wiring. ...
1
vote
0answers
67 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, ...
1
vote
0answers
1k views

Only getting 15-16 volts from Furnace R and C

I recently purchased a smart thermostat. Because it needed a common wire and I only had a 3 wire setup, I ran a new thermostat wire to my furnace. However, I now get only 15 volts (inconsistently, ...
1
vote
1answer
2k views

Thermostat C Wire (Possibly Unconnected)

I purchased a Honeywell RTH6500 Wifi Thermostat, which requires a C wire. My old thermostat showed a connected blue C wire. However, it was battery-powered. If I removed the battery, the thermostat ...
1
vote
1answer
90 views

Connecting Common Wire to Control Board

I have a heat pump and want to add a thermostat that requires a common wire. I have read through many threads that show how to add a wire but I already have a few extra in the bundle so its not so ...
1
vote
0answers
216 views

How to add a C-wire to Weil McLain Boiler

I am having trouble installing a new wireless thermostat to my existing Weil McLain boiler. My existing control wire utilized an Rh and W on the thermostat, but utilized the Y and G terminals on the ...
1
vote
0answers
31 views

Thermostat with an external transformer

I am trying to hook up a Vine TJ-610B-W WiFi thermostat to my heater. The original thermostat had only 2 wires, hooked to R and W, none hiding in the wall. I plan to use an external transformer for ...
1
vote
1answer
2k views

Adding C-Wire for Nest to Triple Aquastat Relay L8148J

Need some extra eyes and advice on how to add a common wire to our current boiler setup. We have a Triple Aquastat L8148E that has 2 wire that connect to our thermostat. Like many before me, I'm ...
1
vote
0answers
61 views

Can I use an available wire as a C-wire by adding it to an unoccupied 24v terminal?

I want to add new thermostats in my home. Luckily, the wiring to my thermostat has an unused wire in the bundle for the required "C-Wire". It has R,G,Y,W, and an unused blue. The thermostat wiring ...
1
vote
0answers
196 views

Thermostat has two wires going into C terminal

Trying to help my dad install his new Nest thermostat - for some reason his thermostat has two wires going into the C terminal. I've searched and cannot find any other question about a setup like ...
1
vote
0answers
152 views

No 24VAC between R and C on Rudd R801 Control Board

I’m replacing a older programmable thermostat with Ecobee 4 which is to control a Ruud R801 HVAC unit installed last year. I have access at the thermostat to a wire (orange) that goes to the C ...
1
vote
0answers
1k 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 ...
1
vote
1answer
607 views

Ecobee 3 lite Installation — Confusion about C wire (on furnace but not at thermostat)

I am about to install the Ecobee 3 lite thermostat. On the thermostat end, there is no C wire - just the typical 4 wires - R,Y,W,... On the furnace end though, there is white C wire too, which I do ...
1
vote
0answers
3k views

Why does my Nest thermostat report error e195 when I try to use the air conditioning?

I had a Nest E installed in February and it has worked really well until it was time to turn on the AC. Now I get random e195 errors (no power detected to the R wire). The most likely answer from my ...
1
vote
0answers
100 views

Why doesn't my thermostat work?

I replaced old thermostat with Honeywell wifi and added C wire from furnace to new thermostat. I left the jumper wire on Rc and R in place and wifi would not come on line. Checked C wire and have ...
1
vote
0answers
426 views

3 wire heating system, has 3 unused wires with 16v, can any be used as a common wire?

I hopefully have a quick question. I am thinking of getting a Ecobee or Nest smart thermostat, but doing my checks/research before getting one for this house. I rent, so I can only do minimal changes. ...
1
vote
0answers
248 views

Thermostat for my furnace has no power during fan-off delay?

I have an older Tempstar 5000 furnace and a newish Honeywell wifi thermostat. The furnace works fine and the thermostat appears to be wired correctly (4 wires including C wire) but for some reason, ...
1
vote
0answers
1k views

question regarding c wire and a nest

I know this issue has been beaten to death but i am stumped and nest support has no clue how to help me. I thought i had the issue resolved but that was wishful thinking. Here is my issue: I have a ...
1
vote
1answer
1k views

Can I run a C wire from Fan Relay

We've just moved into a new home with an heat only, oil, forced hot air furnace. The current thermostats are very old and we'd like to update them to something like a nest. The furnace is currently ...
1
vote
0answers
447 views

Adding a C wire to thermostat with oil berner and AC

I have a oil burner for baseboard heat and forced air AC that is controlled by one thermostat. There are a total of 5 wires coming to the thermostat 2 wires from the boiler and 3 wires coming from the ...
1
vote
0answers
362 views

Installing new thermostat without a C wire. Can I use my heater/R wire instead? Random 13V as well

I'm installing a thermostat, but I don't appear to have a C wire. My old thermostat had R/RH,Y,G,and W. It's an AC system that was setup before I got here. The actual AC unit is a long way away and ...
1
vote
0answers
661 views

Adding a C wire

I know this question has been asked multiple times and I'm going to try some of the methods I have read in other threads but wanted to ask this question since I didn't see anyone else's wired the way ...
1
vote
0answers
1k views

Thermostat will not power on with C wire, but it has voltage

I recently purchased a Honeywell wifi thermostat and tried to hook it up as a replacement for an existing battery powered unit. I have a typical forced air HVAC setup with gas furnace (no heat pump), ...
1
vote
1answer
705 views

How can I implement an unused wire as a C wire for my thermostat?

I have a boiler system that uses 2 wires to the thermostat. I am going to buy a new thermostat that needs a C wire. There is a spare wire not being used and it is not hooked up to anything. How can I ...
1
vote
0answers
4k views

Trane XV80 missing “C” wire at thermostat

I have a Trane XV80 with a 2 stage motor. I'm replacing a Trane TCONT803AS32DAA thermostat with a Honeywell wifi thermostat thinking it would be an easy switch out. However, the older thermostat had ...
1
vote
0answers
341 views

Wireless Transformer no C-Wire

I'm trying to install a wireless thermostat but i ran into issue putting in an external thermostat. I have a 2 Stage Cool / 1 Stage heat system. I have the Red 24V from Air Handler connected to R. I ...
1
vote
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 ...
0
votes
0answers
23 views

Trying to wire for Ecobee thermostat

I have an ecobee thermostat I'm trying to hook up, but I can't figure the wiring out. We have fuel-oil boiler and an AC, with the oil boiler using radiant water pipes (as well as heating our water for ...
0
votes
0answers
26 views

C-wire nest to burnham boiler

Connecting nest learning 3rd gen to burnham series 2 model 203 boiler. I am only using the system for heat. I have three wires at the thermostat R,W and an unused green that I would like to turn ...
0
votes
0answers
34 views

Hooking up Ecobee smart thermostat

I purchased a new Ecobee thermostat. I don't have central air, so heat only. My gas fired hot water boiler has the wires from the thermostats (Red and White) going to the T1/T1 and T2/T2 terminals. ...
0
votes
0answers
20 views

What is causing my ac unit and thermostat not to work with one another

Inside unit and thermostat are not working properly. In the beginning, something needed to be changed in it,it was a small black box and a round cylinder like plug thing.changed out the thermostat ...
0
votes
1answer
51 views

C-wire help needed with Nest thermostat install

My air handler (see photo) connections are G,W,Y,R and COM. The a/c compressor (outside) is connected to air handler Y and COM. I have 5 wires out to the thermostat, G,W,Y,Rh with jumper to Rc, and an ...