Had a thought today, although my if statement 'deadband' will stop the fridge and heater fighting each other, there might still be some chatter around the two extremities of the deadband.
for example, if the temp rises above the setpoint + difference the fridge will come on, once it's dropped below setpoint + difference it will turn off.
How can i tell it to come on at the setpoint + difference but not go off until it hit's the setpoint?