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I have 4 wires at the thermostat and there is no C wire, how do I install my Smart Si?

I have 4 wires at the thermostat and there is no C wire, how do I install my Smart Si?

If you do not have a C wire and are installing a Smart Si, please follow the steps listed here:

  1. Please review the steps below and if you are not comfortable performing electric wiring, please request for professional help
  2. You require an additional 18 gauge thermostat wire*
  3. The assumption is that you have 4 wires available at the thermostat – R, G, Y and W. If this is not true, please contact our support for further assistance
  4. Switch off the HVAC equipment from the circuit breaker
  5. Go to your utility room to access the furnace control board within the furnace equipment chassis (Note the control board could be in the air handler unit)
  6. On the furnace control board, locate the wiring terminals – R, G, Y, W, C
  7. Identify the wires from the thermostat that are connected to the terminals R, G, Y, W, C at the furnace control board
  8. Move the wire at the G terminal to the C terminal
  9. Connect the additional 18 gauge thermostat wire from Y terminal to G terminal
  10. Close the furnace chassis
  11. Back at the Smart Si thermostat, connect R, Y, W and the previous G wire to C terminal
  12. Connect the thermostat and switch on the power from the circuit breaker

(*Your Smart Si box may contain an additional wire)

 

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