The main purpose of dryer booster fan is to increase the air flow through the duct (dryer). If the duct has bends, or the length of the duct exceeds 25 feet, it is recommended to use dryer booster fan. It can improve the drying time by 50%. It can be used with pressure switch or via a current sensing relay.

Pressure switch:

When it senses positive air pressure, it actuates the dryer booster fan automatically. It has an integral timing cycle of a 10 minute ON and 15 second OFF, enabling the fan to restart as long as the dryer is operating.

Current sensing relay:

It senses the dryer current drawing between 1 and 50 amps. At this time, it turns on the dryer booster fan by closing a relay contact. When current drops below threshold, it turns off the fan by opening the relay contact.