3-Point Controller - how it works!
A Three-point controller is a discontinuously operating controller with three output states. How do so?
An example where a three-point controller can be used is a heating / cooling thermostat. Below the minimum temperature it switches on a heater, above the maximum temperature it activates a cooling unit. Within the range between minimum and maximum temperature both outputs are switched off.
3-Point-Controller Appliance
However, a three-point controller can also switch two-stage actuators. For example, gas or oil burners with two power levels, wherein when falling below the lower setpoint, the second stage is added.
3-Point-Controller Appliance