samtree In the manual it says “Setting the hysteresis parameter P1: This sets how much change in temperature must occur before the relay will change state. For example if set to the default 2oC and the the trigger temperature has been set to 25oC, it will not deenergise until the temperature falls back below below 23oC. Setting this hysteresis helps stop the thermostat from continually triggering when the temperature drifts around the trip temperature.” Well, this is wrong. When in C (cooling) mode, the relay is energized (closed) when the probe temperature reaches t = Trigger Setting + Hysteresis setting (P1) and de-energizes (opens) when while going down (cooling) it reaches t= Trigger Setting. So, in the example given in the manual, the relay will close at t=25+2 = 27 Celsius, and will open again when t=25 Celsius is reached. Now, for the question asked: Set Trigger Temperature at 4 Celsius, and Hysteresis (P1) at 3 Celsius. It will close at 4+3 = 7 Celsius, and open again at 4 Celsius.