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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How can I install a Honeywell RTH65800WF Wifi thermostat?

I am having some difficulty figuring out the correct wiring for my new wifi thermostat. Before I bring out the A/C technician, I was wondering if anyone here might be able to help? Searched other ...
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Is it possible to use add-a-wire with my current configuration to add a C-Wire? [duplicate]

I only have four wires: Red, Blue, Yellow, and Green. My old thermostat jumps the R to RC and leaves C empty. I have a new thermostat that wants 5 wires, but I don't have C. I am not sure what the ...
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How to connect thermostat C wire to Weil-McLain CGa boiler? [duplicate]

I have Weil-McLain gas boiler for hot water heat and going to install WiFi thermostat that requires common 24V 'C' wire. I do have a free wire in the cable but cannot figure out where should I connect ...
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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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Options for adding “C” wire to thermostat [duplicate]

Possible Duplicate: Options for adding “C” wire to thermostat I am upgrading to a newer thermostat that requires a constant 24 volt feed, I have an extra (unsused) wire in the cable ...
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I changed my thermostat, not my heat does not work… help!

I know I made a mistake, but here's the storey. When I was hooking up the new thermostat I did it with live wires, and I used metal pliers (metal touching metal). The wires may have also touched ...
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Does it matter which 24v line I use to splice a common wire from?

I have a RayPak boiler that currently has a W and R wire only. In wall i have a 5 connector thermostat cable so I have three extra wires I can connect to. I'm a little unclear if it matters if i ...
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1answer
737 views

Can I use a ground instead of a dedicated C wire for a thermostat

My new wi-fi thermostat requires a common wire coming from the 24 volt transformer. Rather than running an additional wire can I ground the common side of the transformer to the building steel ( this ...
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Using a ground wire as a thermostat C

Just theoretically, A C wire is just a return for 24v transformer right? So if you were in a situation where you have access to the slab, or just a standard outlet or switch receptacle could you wire ...

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