The fans may be used for cooling, humidity reduction, air changes and to bring in ambient CO2 (if CO2 injection is not used at that time). During the day when CO2 is being injected, other means to control temperature or humidity will be used in preference to the fans which will only be used to force an occasional air change and provide a fail-safe if the aircon or dehumidifier fails.
For simple systems that have CO2 injection but do not have aircon or dehumidification, the controller will operate as a cycle timer system with three timed phases
- Fans on,
- Fans off, inject CO2
- Stop injecting CO2 and wait while plants absorb CO2 then repeat cycle.
In this mode, the controller will self-adjust the timings if it finds that CO2 is being wasted due to the fans being forced on by heat or humidity build up before the plants have time to use the CO2.
If this situation is too bad it will stop injecting CO2 and will revert to maximum venting (within temperature limits) to bring in as much ambient CO2 as possible.