There’s one piece of this puzzle that I’m hung up on.
It appears that we need a custom thermostat to control both cooling and heating. One for each. Yes?
I built a 3-relay device with a Wemos D1 Mini, flashed it with Tasmota, and turned on auto-discovery and the 3 relays show up as 3 separate switches in HA, along with the Temp and Humidity sensors.
Now, in order to fire up the A/C, I need to trigger the cooling relay and the fan relay. I’ve made that happen through NodeRED. To trigger the heat, I need to kill the compressor relay and switch to the heating relay, but leave the fan on. I’ve done that also in NodeRED.
So, I’ve basically been able to create logic in NodeRED that ensures that the compressor is never on without the fan being on, and that the heater is never on without the fan being on, and if the cooling is turned on while the heater is on, it automatically turns the heating off, and vice versa.
What I can’t grasp is how to have a single thermostat control this setup whereby there is a toggle between heat and cool and everything else is automatic.
Are we truly forced to have two separate thermostats in the DIY world of thermostats or am I missing something about “everything climate” in HA?
I have a very similar problem. Though I have tried a different method and found a different issue. I used ESPHome and the Bang Bang thermostat. This allows me to use the LoveLace thermostat card to control both heating and cooling. The problem is it doesn’t control the fan, which I could fix with simple automation, but the Bang Bang thermostat doesn’t allow hysteria and lock outs. I won’t to ensure that somebody can’t go from heating to cooling without a delay.
I managed to get the fan control handled through NodeRED, and hadn’t heard about Bang Bang until you mentioned it in your OP about it. What are hysteria and lockouts?
Sorry my typo. I meant to write hysteresis. A normal thermostat if set to say 20, will allow the heater to go to say 20.5 and then shut off and restart at say 19.5. The reason for this, is if it turns on and off at exactly 20, it will be continually turning on then off and so on. My understanding with HVAC systems to protect the system, they do not allow you to go from heating to cooling or from on to off and on again without a delay or lockout. With the bang bang controller, I have go from heating to cooling and back with no delay, this would put significant load on the HVAC