The KISS method is one of my favorite acronyms, keep it simple stupid. It is not about insulting a contractor about their knowledge, it’s about making things easy. Decades ago the PENN electric switch company, bought by Johnson Controls in the 1980s, made a line voltage thermostat that required no outside power to operate. No internet of things, no calibration or BSME required to operate it.
We needed an thermostat to operate a Loren Cook Gemini exhaust fan to remove hot air in a lobby where we installed a condensing unit. The VRF unit is inside for demonstration purposes and when the training room need a lot of cooling we need to exhaust the heat outside. The Penn thermostat simply turns on the fan when the room gets above 78F. Simple 120V one wire current interruption when room temp is OK, engages when the room gets hot. So simple!
Keith Glasch's Blog 