CBD.. Backdraft Shutters for Centrifugal Roof Units
CBD backdraft shutters have a galvanised steel frame and extruded PVC flaps; the flap spindles run in nylon bushes.
For high temperature applications the flaps can be fabricated from galvanised steel or aluminium. High temperature conditions must be nominated at the time of enquiry.
These dampers are designed to fit inside the unit base and to be positioned on the roof curb before fitting the roof unit.
The curb surface must be flat to permit an airtight seal.
These are supplied as standard for twin fan units, for which they are an essential item, to ensure there is no short-circuiting of the airstream.
They are an optional extra for single fan units.
The pressure loss through the dampers must be added to the system resistance before selecting the fan.