These ceiling dampers are Classified by Underwriters Laboratories, Inc. as to heat barriers in the Fire Resistance Directory under the category of Ceiling Dampers (CABS). Refer to the Classification information in the back of the Fire Resistance Directory regarding the use of these dampers in the various floor-ceiling or roof-ceiling assemblies. Ceiling dampers and the associated components (surface mounted diffusers or grilles, ducts, etc.) which are to be constructed of steel, are installed in the ceiling to maintain the hourly ratings of the floor-ceiling assemblies which are rated 3 hours or less.
The damper / surface mounted diffuser shall be installed as shown on the installation sheet. The damper shall be installed as shown on the installation sheet. 12 SWG hanger wires, minimum of 3 wires are to be used to support the round ceiling damper.
Optional support method. The ceiling damper / surface mounted diffuser assembly is to use two #16 gauge cold-rolled steel support channels.
The two 11/2 inch or 2 inch, No.16 gauge cold-roled steel channels with 1/2 inch flanges, are to be attached to the top of the damper frame with 3/16" bolts of 3/8" minimum length. A minimum of two bolts per damper are required. Each channel is to be supported at each end by 12 SWG wire attached to the structural members.
All hanger wires shall be supported directly from the structural members of the floor or roof by vertical ( not diagonal) hanger wires.
Cold-rolled channels shall be used as required to insure that the grid and damper are supported from the structural members by vertical hanger wires (not diagonal).
The flange on the surface mounted diffuser at the ceiling membrane level shall provide a minimal 1" support for the ceiling panels.
Size of the hole cut in the panel for passage of the duct drop shall be no more than 1/8" larger than opening for the damper.
When cutting of a main runner or cross tee is needed, a 1/2 inch clearance must be maintained between the cut end of the main runner or cross tee and the damper. A 12 SWG hanger wire shall be installed near each end of the cut main runner or cross tee. No more than one main runner or cross tee may be cut when penetrating the ceiling membrane.
The steel diffusers shall be attached to the damper with No. 8 sheet metal screws, 3/16" tubular steel rivets, 3/16" diameter by 1/2" long steel bolts, or 1/4" tack welds. Minimum of three connections, 6" OC. A steel clamp or No. 16 SWG minimum steel wire shall fasten the flex air duct to the damper when flex air ducts are used to connect the main duct to the damper/ diffuser assembly. The flex air duct shall be Class 0 or 1 and bear the UL listing Mark- refer to the UL "Gas and Oil Equipment Directory". Maximum length of flexible air duct shall not exceed 14 ft in length. The flexible air duct shall not rest on the back surface of the ceiling grid or panels and provide a minimum of 4" clearance.
The flexible air duct shall not interfere with the closing of the damper.