Tjernlund EF-8AUTO Automatic Duct Booster Fan, 8"

The EF-6AUTO and EF-8AUTO Duct Booster fans can be installed in less than 10 minutes and automatically operate in sequence with your furnace or air conditioner. Both units feature a pressure control which automatically activates the fan based on the airflow created when a furnace or central air conditioner blower turns on. The fan then runs checking to see if airflow from the furnace or air conditioner blower can still be detected every few minutes. The fan turns off when this airflow is no longer detected so it runs only when there is warm or cool air to distribute. Simply insert it into the duct run and plug it in.