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No C wire - using a external power supply to power your thermostat

Last Updated: Jul 15, 2013 04:18PM UTC

If you don't have an extra wire in the wall, you can power your thermostat with an external transformer. (24VAC @ .5 to 1amp transformer) If you don't already have one, you can purchase one from our online store at Once you have a 24VAC transformer, follow the steps below to apply power to your thermostat:

  • Connect one wires from the external transformer to the "C" terminal on the thermostat.
  • Connect the other wire to the "Rh" terminal
  • Plug in your external transformer
  • Verify your thermostat has power by removing the batteries

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