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Welcome to the homie_heatPump wiki!

For starters, thought I'd show some pics. of my setup and use of the ESP8266 with the heat pump. By way of explanation, yes this was a mini-split unit (1.5Ton) but, right from delivery, I'd cannibalised the interior unit and the external compressor and condenser are now hooked up to an A-Coil in my furnace for central air!

Why? Well, I get much higher efficiency unit this way without the cost. Also, I like the TXVs being electronic and outside rather than in the furnace and they are way more efficient and maintenance free than mechanical ones. I don't expect many people to do this but still, this project is likely useful for others.

How does it work without the interior fan motor? Used a good'ol 555 timer circuit to fool the heat pump controller into thinking that the fan was there. The air handler/furnace has RS485 standard communication and there is need to get internal fan speed to the air handler. Thus, this project is borne. To link this common unit to N.American 'standard' (It is called something different by every brand and the open alliance page went dark a few years ago. Thus, the culture is defined, need I say more.).

Remote and display board that are being replaced by this project :

Location of new A-type evaporator coil (a 2Ton aluminium Goodman one with the orfice removed -- VERY IMPORTANT as electronic TXV valves already perform this function in the compressor unit outside):

Test rig with NodeMCU V1.0 (ignore the other unconnected chip, it is for another project), a level converter project board, and an 8-pin connection header :

Final device after testing: