Primair Fan Speed Controller can control two sets of fans (exhaust and intake or all exhaust) with minimum speeds set for both.
Simply set the desired maximum temperature and place the probe where you want the temperature read, usually among the plants. When the temperature gets higher than set the fans will start up and continue changing the air until the temperature is lower than the preset. Capacity for 2 x 460 watt fans. Idling speed of the fans can be set from off to gentle ventilation. 12 month guarantee.