The best climate is a constant climate.
When the lamp in your grow cabinet turns on, the temperature in the cabinet will rise. The build in air extractor removes this heat from the cabinet. As soon as the lamp switches off again, the temperature will drop and your air extractor will therefore have to discharge less warm air. The air extractor could therefore run at a lower speed when the light is off. This saves energy, ensures a more stable climate and makes the cabinet very quiet.
The fan controller works very simple. You plug it into one of the sockets on the ceiling of your grow box and hang the temperature sensor at the height of the plants. Plug the air extractor into the fan controller. Please note that when you use the fan controller in combination with a GT 125 2-speed extractor (Bonanza 1m2) that it is set to position 2.
There are two buttons on the controller. With one you set the desired temperature and with the other the minimum speed of the extractor.
Example: You have set the temperature to 24 C and the minimum speed to 25%. When the temperature rises above 24 C, the extractor will run at 100% of its power. When the temperature drops below 24 C (light off), the extractor will run at 25% of its power.
Your cabinet is now inaudibly quiet and the air extractor still runs at enough speed to maintain underpressure in your cabinet and thus prevent unwanted smells from escaping the cabinet.