Here is my radiator or roomheater that heats the room with a heatpump.
Fully controlled by an Arduino Uno.
The Uno reads tempsensors for roomtemp, evaporatortemp, condensertemp and compressor suctiontemp.
From that it Controls the evaporator fan and condenserfan by PWM and compressor on/off with a SSR.
It also calculates when to defrost and pressure equalize.
The GUI runs on a 20x4 LCD.
When running it consumes 130watt but puts out up to 500w heat.
This is the SSR i use to control the compressor.
A Carlo Gavazzi RP1A23D3.
From a 3-32v DC input it can switch a 230v 2amp inductive or 3amp resistive AC load.
So it is connected directly to an Arduino digitalpin switching 230vac on the other side.
No additional Components required.
So not a question, but a brag? I like it.
That's a very interesting project. Did you use the compressor/evaporator/condenser from a commercial air conditioner?
I used a dehumidifier.
I did not open or change the R134a circuit but built new airchannels instead.
A singel fan for the evaporator and 2 parallel fans for the condenser.