Ceiling Radiation Damper Model CRDD
The Model CRDD damper is described as a rectangular butterfly style damper mounted in the base of a register-box plenum (boot). The damper blades and frame are constructed with G60 roll-formed galvanized steel with minimum thickness of 24 GA. The blades are insulated with nominal 1/4-in., 8-lb/ft
3 (128 kg/m
3) ceramic fiber insulation. The damper is held open with a 212 °F or 165 °F fusible link and closes by a spring force. The maximum damper size shall be of 256 in.
2 with no dimension greater than 16 in.
The register-box plenum has two options for the construction material. One option is construction with steel and second option is construction with duct-board. The steel register-box plenum is constructed with G60 galvanized steel, maximum thickness of 24 GA and minimum thickness 28 GA. As an option for the steel register-box plenum, the register-box plenum can be insulated with 1-in. thick, fiberglass insulation with a minimum R-value of 4.2. The duct-board register-box plenum is constructed with minimum thickness 1-in. duct board, with a minimum R-value of 4. The joints and seams shall be per Royal Metal Products installation instructions. The register-box plenum variations include inlet duct configuration, use with a register or sleeved for duct connection, and mounting options.
The Royal Metal Damper Model CRDD uses register-box plenum models 557RD, 557RDD, 556RD, 556RDD, 241FRD, 241RD, 243FRD, and 243RD.
Royal Metal 557RD and 557RDD
The 557RD and 557RDD are register-box plenums constructed of duct board, with 1 in. minimum thickness and minimum R-value of 4. The 557RD is designed for installation in the ceiling and for use with a register. The 557RDD has a sleeve that extends below the ceiling for duct connection to the air handler.
Royal Metal 556RD and 556RDD
The 556RD is a steel register-box plenum with round connection collars on the side of the plenum. The 556RDD has a sleeve that extends below the ceiling for duct connection to the air handler.
Royal Metal 241FRD and 241RD
The 241FRD and 241RD are steel register-box plenums with round connection collars on the top of the plenum. The 241FRD plenum has a frame around the bottom to facilitate installation with boot rails. As an alternate to the boot rail, the plenum can be installed with a minimum 1-1/2- × 1-1/2-in. × 22-GA angle. The 241RD has no frame and requires installation with a minimum 3/4- × 3/4-in. × 16-GA angle.
Royal Metal 243FRD and 243RD
The 243FRD and 243RD are steel register-box plenums with tapered connection that turns 90° into the round collars out the side of the plenum. The 243FRD plenum has a frame around the bottom to facilitate installation with boot rails. As an alternate to the boot rail, the plenum can be installed with a minimum 1-1/2- × 1-1/2-in. × 22-GA angle. The 243RD has no frame and requires installation with a minimum 3/4- × 3/4-in. × 16-GA angle.
Ceiling Radiation Damper Model CRDS
The Model CRDS is described as a rectangular single-blade damper. The construction and boot requirements are identical to the CRDD. The only difference is the CRDS is a single blade damper with a maximum size of 144 in.
2 with a maximum dimension of 14 in.
The Royal Metal Damper Model CRDS uses register-box plenum models 241FRD, 241RD, 243FRD, 243RD, 509RD, and 557RD, and 556RD. The 241FRD, 241RD, 243FRD, 243RD, 557RD, and 556RD models are described with Ceiling Radiation Damper Model CRDD.
Royal Metal 509RD
The 509RD is an insulated steel plenum with a duct connection on the side.
Ceiling Radiation Damper Model CRDR
The Model CRDR damper is described as circular butterfly style damper mounted in the duct connection collar. The damper blades and frame are constructed with G60 roll-formed galvanized steel with minimum thickness of 24 GA. The blades are insulated with 1/4-in., 8-lb/ft
3 (128 kg/m
3) ceramic fiber insulation. The damper is held open with a 212 °F or 165 °F fusible link and closes by a spring force. The duct connection collar is round, for nominal duct sizes from minimum 4-in. to maximum 10-in. diameter and is dependent on the grille size.
The insulated register-box plenum (boot) is constructed with maximum thickness of 24 GA and minimum thickness 28 GA, G60 galvanized steel with a round duct top inlet. The nominal height off the boot and collar is 7-1/2 in. and is in sizes for a rectangular opening for steel grille sizes ranging from 8- × 4-in., minimum, to 14- × 8-in., maximum. The inside of the register-box plenum has minimum 1-in. thick fiberglass insulation with a minimum R-value of 4.2.
The Royal Metal Damper Model CRDR uses register-box plenum models 505RD and 507RD.
Royal Metal 505RD
The 505RD is a register-box plenum configured with the duct connection on top with the damper contained within the duct connection collar. The duct connection is parallel to, and center with the grille.
Royal Metal 507RD
The 507RD is a register-box plenum with the duct connection configured 45° offset relative to the grille inlet with the damper contained within the duct connection collar.
| Test Standard |
Test |
Result |
| UL555C, Section 6 |
Fire Endurance Test |
1-hr Combustible Construction
3-hr Noncombustible Construction |
| UL555C, Section 7 |
Closing Reliability Test |
Pass |
| UL555C, Section 8 |
Salt-Spray Test |
Pass |
| UL555C, Section 9 |
Spring Closing Force |
Pass |
| UL555C, Section 10A |
Dynamic Closure Test |
Not Applicable for Static Dampers |
Tested and Approved for installation in fire resistive rated assemblies incorporating air duct outlets penetrating protective ceilings of gypsum wallboard, concealed grid suspension systems, or exposed grid suspension systems, for 1-hr rated combustible construction and 3-hr rated noncombustible construction.
