What for? If you are going to put one up where the thermostat is and plug it into a power source, the two wires are right there to close or open and control the furnace. What advantage would a second Pi down at the furnace do for you?
I don't know about that. My Pi has been controlling my heating 24/7 for years now and has saved me a lot of money by only turning on the heating when needed based on the temperature and time of day.Paul Hutch wrote: ↑Mon Feb 11, 2019 3:28 pmThis is one of those projects that will take far more time and cost far more money than any plan will estimate. Plus it may cause grief if bugs in your custom system leave the heat off and you get real cold, leave it on wasting oil, or off while your away and the house pipes freeze and your insurance won't pay up because your custom device caused the problem.
Considering a good quality Honeywell LCD readout battery powered thermostat can be bought off the shelf for less than the cost of a RasPi 3 alone, I'd have to be desperate for a project to do before I'd tackle this project.