These are air filtration equipment normally assembled in the factory ready for installation in duct or plenum systems. The air is achieved by viscous impingement principle due to the filter media that is normally impregnated with adhesive oil. When the filter media reaches a preset value of pressure drop a pressure switch through an electrical circuit gives to the drive motor the input to operate unwounding a new part of media till to reach a lower value of pressure drop. Two side channels guide the filter media during the uncoiling. In addition, a metallic support grid, mounted on the air leaving side, prevent any media deformation or flexing caused by the crossing air pressure. These important features ensure air – tight seal between the frame and the filter media.
The drive motor is actuated by a differential pressure switch. In some cases, in accordance with the working installation, an adjustable timer can be provided in place of a pressure switch. Therefore, the electrical control board of the electric gear motor can be supplied in two versions: the first, standard with pressure switch control, the second, on request, with timer control. To make the working and service operations easier the electrical board is provided with manual stop and feed media manual control. A switch stops the electric motor avoiding the complete roll unwounding preventing therefore the plant system from working without filter media, while a signal light appears on the control board.