I bought a nest gen 2 thermostat to play with a open source project that revives old nest thermostats (https://nolongerevil.com/). Since I don’t want to install it into the home, because it will be a toy. I was thinking of building a test rig using a arduino or esp32 to simulate a HVAC and indoor temperature. I’m IT guy, not a HVAC guy, I think this would be a good learning project. Any suggestions?
HVAC-R tech here.
Not sure what you mean about simulating high temps on the thermostat. If you want to trick the thermostat into seeing a higher temp than it is actually at then you would need to find the temp sensor on the thermostat (usually a thermistor) and replace it with something where you can manually control the input like a potentiometer if there was a thermistor there.
If you’re talking about simulating calls from your thermostat to your hvac system, then you can usually do that with just some jumper wires if your hvac system has a built in transformer (almost all new systems do). You just remove the thermostat and jumper the hot wire (R or Rc) to whatever call you want to make.
Edit: I should probably note that if you accidentally jumper anything to ground or to common then you will likely trip the breaker or blow the fuse on your systems transformer. If you do that then you’ll need to find that transformer (usually in the airhandler, assuming a standard residential split system) and reset the breaker or replace that fuse before your system will work again.