Thermostat C Wire: Everything you need to know about the “common” wire

Back in the olden days, thermostats were simple on/off devices that didn’t need their own continuous power supply.  Modern thermostats with Wi-Fi and backlit display, by contrast, need a steady supply of juice. The C wire, or “common wire” enables the continuous flow of 24 VAC power to the thermostat. Technically speaking, power flows from…
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