The EFC18 is an electronic control unit that connects to your chimney fan to give you control over the fan.
The control unit comes with a temperature sensor, which is installed under the chimney fan. It sends a signal to the control unit when the temperature reaches 20, 40, or 80 °C (depending on the setting), and it turns off the fan after 45 minutes. This ensures complete combustion of all combustible materials in the stove.
On the front of the compact control unit, there is a knob and a small display that shows which of the 9 steps the chimney fan is set to.