Thermostat wiring question Leave a comment

Got a free smart tstat from the electric company. Took off old tstat took picture, went to basement to check colors on the unit and r, w, and g matches up but the blue wire is connected to c on hvac board and y on tstat. Y is unused on hvac board.

Installed a c wire kit that came with tstat, which connected y and g at tstat to a diode that returned to hvac on blue to connect to a box with other wires. Hooked everything up per instructions got beat working but for ac, the compressor doesn’t come on, the fan does.

Could I remove the c wire kit revert all wires back to normal and jump y to c on tstat since y on tstat is going to common on hvac and all works that way.? enter image description here

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Could I just g for common instead? I work with industrial hvac units but this small thing is baffling the hell out of me.

*** EDIT ***
@ThreePhaseEel
@jwh20
@Harper – Reinstate Monica

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2 wires – red and white exiting to the right on lower wire are going to the condenser outside.
4 wires – red, white, green, blue exiting to the right on top wire are going to tstat.
4 wires – red, white, green, blue exiting bottom conduit go to air handler board

So, blue wire from c terminal on handler goes to white wire on condenser, blue wire from y terminal on tstat goes to red wire going to condenser.

red, green, white from tstat go to red green white on handler.

Only 4 wires to and from tstat
2 wires to condenser
5 wires going to air handler (Hey, theres that yellow wire)

How can I hook up my emerson sensi smart tstat?

Right now I am using green as common to get power to tstat, heat and fan work, condenser works but no fan.

How to I wire tstat as is or use the included c wire kit?

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