Up-Blast Stack Cap combination non-back draft damper is applied at the terminating point of a vertical exhaust stack. The Cap has two damper blades that open automatically when the fan is turned on. When the fan is at operating speed, rain and snow are pushed away from the open duct. The damper blades remain at a slight angle when they are open. At the moment the fan is turned off, the blades drop and close off the open duct. This stops rain, snow or outside air from entering the duct system.
Most state and local municipalities “require” an Up-Blast Stack Cap as the terminating point of an exhaust duct that is directed to the atmosphere. It is also recommended to terminate the exhaust duct 6 feet above the roofline in a vertical fashion. This prevents the contaminant from being drawn into the heating or air conditioning units, open windows, make up air units and other open vents in the roof. For additional information, please refer to NFPA 33 and NFPA 91. The Code booklets can be obtained from the National Fire Protection Agency, Quincy MA, (617) 770-3000 or www.nfpa.org.
These are also commonly known as upblast, exhaust roof cap, exhaust cap, roof ventilation cap, exhaust rain cap, vent hood roof cap, exhaust rain flap, rain cap roof, up-blast, 8 inch rain cap, upblast exhaust fan, roof vent pipe cover, exhaust pipe flapper, rain caps for vent pipes, pipe rain cap, upblast fan, upblast roof exhaust fan, stainless steel rain cap, 6 inch exhaust rain cap, upblast ventilator, 6 exhaust rain cap, exhaust cover flap, or simply stack cap.
** To operate damper blades a minimum of 2,500 fpm of air velocity is required plus a 1/4″ of static pressure loss. **
Allow 4 to 10 working days for fabrication.
Other sizes available, call for pricing.
Collar sized to slip OVER spiral pipe.