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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Do I have to run an extra wire all the way to my new thermostat, or just to the “router”?

I've got an older home (plaster walls) and an older furnace, It's a Peerless. My current thermostat is located on my main floor and only has 2 wires to it, red and white. I should mention that my ...
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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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Can I install a Honeywell WIFI Thermostat?

I have done quite a bit of research and have not been able to find an answer I am looking for. I currently have a manual digital thermostat that is not programmable made by Braeburn. My system is a ...
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282 views

No electricity going to thermostat

Our old thermostat is working but I want to change to a new one (nest thermostat). I have two exact HVAC unit at home. I change one it works but when I change the second one it doesn't work because ...
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How can I add a C-wire to a Venstar T5800 thermostat?

I am trying to replace my existing thermostat. My old thermostat has: Rh, W (coming from the heating unit). Rc, Y, G (coming from the AC unit). On the Venstar T5800, I can map as follows: Rh+Rc ...
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Please help establishing a C wire for new tstat

I bought a new WiFi tstat as a replacement. The tstat controls my second floor hot water baseboard heat and my central air conditioning. I've located all the wenter image description ...
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401 views

How to add a 'c' wire common wire to this system

I have a galaxy cast iron gas boiler and i'm trying to determine where to attach the 'c' wire on the furnace for my new wifi thermostat. The cable is an 18/5 but is only using 2 of 5 wires currently. ...
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How do i connect the common c wire in a carrier air handler?

I need help in determining where to hook up the common c wire for my new thermostat. The carrier air handler appears to be a little more complicated than others.