Switching On/Off (2-Point Control)
It is a simple control method, widely used in conventional thermostats, where the setpoint temperature and two values of hysteresis around the setpoint are required. It prevents a continuous switching between the two modes.
The same behavior applies with cooling systems.
Features
The downside of simple control is that the room temperature is not constant; it changes continuously. This can reduce comfort, especially if the heating and cooling systems are slow to react. To address this, you can set a small hysteresis. However, this increases the switching frequency, leading to more wear on the drives.
The temperature overshoot above or below the hysteresis apparent in the diagram is caused when the heating/cooling system continues to emit heat or cold into the room after it has been switched off.
Setting hysteresis
Small hysteresis: leads to small fluctuations, but frequent switching.
Large hysteresis: leads to big fluctuations, but infrequent switching.