Questions tagged [common-wire]
The common-wire tag has no usage guidance.
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External (C Wire) Power Supply Use for Cooling Only unit
Question regarding using an external 24V power supply to provide power to a smart/WiFi thermostat. I’m not clear on why both Honeywell and Emerson/Sensi docs state that the use of an external power ...
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Another C-wire for Nest thermostat question
Some background first. 30-ish year old furnace/boiler with a zone system and six zones. This was my parents full-time residence in rural Maine, but after my father passed away in 2022, and my mother ...
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Connect c wire at old furnace
I don’t have an air conditioner and have the same issue. Blue wire for c at thermostat but blue wire not connected to anything at old furnace. The blue wire is with a red wire and a beige wire near on ...
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How to make c-wire to a new boiler using Fast-Stat common maker?
I'm seeking assistance regarding connecting a C-wire (for Ecobee) to a new boiler using the Fast-Stat common maker. The new boiler currently has two thermostat wires available for connection. However, ...
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Ecobee Thermostat / Common Maker / Gas Valve
I have a two-wire thermostat and an old forced air gas furnace in my house. When you open up the cabinet, inside you find a Dayton 2E228 Gas Valve and it is wired to an external 24VAC Transformer ...
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Is it ok to supply power from one device a use Common on another?
I have a valve relay with R and W going to a stat, and there’s a spare wire I want to connect to a C wire. The relay doesn’t have a Common and I need the common for a wifi stat. I have a separate zone ...
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Can neutrals be landed in an old panel which acts as a junction box?
I have a metered panel which had been stripped down and wires jumped over to new panel. The feed is still here but also jumped over. Can I land my neutrals from the new panel inside of the old main ...
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Which Circuit Does this Switchbox Common Wire Belong To?
I'm replacing a single-pole switch with a Lutron Caseta, in a switch box that houses two switches, each on a different circuit. The old switch that I've removed was connected to two wires: line (red ...
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C terminal voltage on AC control panel
My smart thermostat shut itself down reportedly (as it ran some time on internal chargeable battery and I browsed through the settings) because the C terminal stopped receiving 24V power supply. That ...
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Can I connect my thermostat's R and C wires directly to the transformer?
One day my parent's furnace and thermostat stopped working. The thermostat is a smart thermostat that depends on 24volts to the R and C wire.
We measured voltage between the R and C wire and was ...
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Where do I connect the C wire in my furnace?
I am upgrading my thermostat to a Nest, and would like to add a common wire. My current furnace controller doesn't have a C terminal, but the current thermostat wire has 2 unused wires (black and blue)...
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