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momo9864 05-22-2013 08:26 AM

How to Install NEST thermostat with Trane Axiom Water-Source Heat Pump
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Hi, I recently tried to install nest in my condo with my trane heat pump system (Trane Axiom Water-Source Comfort System Model GEH/GEV). We have a brown Y-wire, green G-wire, white O/B-wire, red R-wire, and blue C-wire. I've attached these all to the corresponding ports on the nest. (images attached)

The heat seems to be working fine, but the cooling does not work properly.

Our home is typically around 78 degrees, and we set the thermostat to 73 degrees. It will cool to 75 degrees, but it never gets any lower than that, the fan never stops running, and it typically goes back up to 77 or 78. Since the fan never stops running but the house doesn't get any cooler, I assume that the condenser turns off for some reason. Once it goes back up to 78, if we turn the nest off and back on again, it seems to reset the condenser and it will go back down to 75. But then the cycle repeats. We have to reset the nest every 30-60 minutes to keep it at 75, when we would ideally like it to be 73.

We've tried connecting the red R-wire to both the Rc and Rh terminals, but it doesn't make a difference. These are supposed to be internally connected anyway.

We've reset the system several times but that doesn't help.

We also tried disconnecting the C-wire, but that caused the unit to shut off completely after about 5 minutes with an error message that said there was no power to the Y-wire. We disconnected and reconnected the Y-wire several times, the system would start again, but turn off again with the same error message after 5 minutes. We ended up reconnecting the C-wire and that issue stopped, but we still have the problem with the house not completely cooling down, and then re-heating back up to 78.

Are the wires hooked up properly? Is there anything else we could try?

hvactech126 05-22-2013 09:19 AM

NEST has many Heat pump issues. Go with a known, good thermostat manufacturer. Ditch the NEST!... too many problems.

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