A HVAC Automatic Roll Filter, also known as automatic roll filter, refers to an automatic air filter unit using disposable or washable filter media taking the shape of a roll simply spooled from the top to the bottom.
The most common automatic control on the roll filters is the actuate movement of the filter media by a pressure differential system where the motor is triggered-off to stop the cloth in position when sufficient new area is exposed to lower the differential pressure to the original value.
The roll, in the case of a disposable media, is replaced with a new spool when the whole length has been run through while, in the case of a washable media, it is washed online within a cleaning bath. The media can be either dry or oil coated.
These filters can operate horizontally or vertically face downward as well as straight up and are usually used as a primary filter in an air filter unit.