Thermostats are engineered and designed to run an HVAC system, 24 hours a day, 365 days a year. There is a lot more to a thermostat than simple on/off control. There are PID Control loops running, multistage heating and cooling, safeguard logic to prevent equipment damage, fan control, auxiliary and emergency heating, etc...
I would never trust a home automation hub to control my HVAC. I’d use it to set a target temperature based on whatever logic one desires, but I’d always let a thermostat handle the actual control.
We are talking residential here. Many hvac units are very simple on/ off. Multistage = two sage, some units require one more wire attached and easily controlled as is a reversing valve for a heat pump. If you have a Goodman or Amana, their to stage is controlled by the condenser and is operated by a straight cool or heat call, a algorithm takes care of the second stage by the parameter you program into the unit during setup and has nothing to do with the thermostat at all. Using a relay setup you will in fact have much more control of pre and post fan operation and be able to do things such as run the fan for 30 minutes after a compressor call is complete to dry the evaporator coil. Also using this setup would enable more control off the two stages for dehumidification and also control of emergency heat. Thermostats are mostly stupid devices and if you dive into a HVAC forum you will see that ALL techs jump at the chance to throw Nest thermostats in the trash.
My Trane is an older (regular ZWave with Beaming, 40kbit) that I used prior to the Nest (gen1) stuff. It works fine, has local schedule, etc.
I currently have the local schedule disabled, and I’m trialing hubitat’s Thermostat Scheduler. There are a few kinks to get ironed out there, but it generally works fine.
It’s very vanilla looking, details are in the post, incl a picture :
I forgot to ask you back when we were talking, does the Trane allow you to feed it an external temperature? I.e., create a virtual temp sensor that is an average of a bunch of sensors in my home, and feed that temp to the trane and it uses that rather than its internal temp sensor to manage HVAC?
The units I’m using are fairly basic and don’t support remote temperature sensors. I’m using the HE Thermostst Scheduler app to control them, and it doesn’t look like it (currently) has that functionality either.
