Over the last four months, I've experience a problem in the morning when the Nest schedule is set to increase the temperature from 68° to 70° at 5:00 a.m. The problem described below hasn't happened at other times.
My furnace is a Trane gas-fired hot air. Here are the facts:
- The Nest is calling for heat. The actual temperature is several degrees below the calling temperature.
- The fan (air handler) is running, but it is blowing cold air.
- The Trane LED's are slow-blink green (standby, no call for heat), and red every 20 seconds (normal - alive). Slow-blink green and red every 20 seconds indicates no call for heat.
I'm able to fix the problem by turning the Nest well below the calling temperature, and then resetting the Trane by turning it off, waiting 30 seconds, then turning it back on. I then set the Nest to the desired temperature, and the system heats normally.
Note that I have a C wire installed (see screen snip).
Initially, my HVAC tech thought this was a problem with the Trane, so we replaced the control board and the flame detector. However, the problem continues to occur most mornings when the schedule calls for the temperature to go from 68° to 70°.
I would appreciate feedback from anyone who might have an answer, or has experience the same issue. As of now, the HVAC tech (Nest-certified) is leaning towards the possibility of an issue with the Nest.
For what it's worth, here's a pic of the old thermostat that the Nest replaced. Note there is no "Common" wire. This thermostat had batteries.
