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Field Installation of Steel Plenums for CRD-1WT
1) The steel plenum box shall be a minimum of 28 ga. (0.47 mm) of galvanized steel.
2) The inside width x length dimensions of the steel plenum shall be sized no greater than
damper frame. The maximum plenum height shall be 14 in. (356 mm) as illustrated below. The plenum should be
sized to provide a snug fit over the damper frame.
3) The plenum duct collars shall be a minimum of 30 ga. (0.4 mm) galvanized steel. The total area of the plenum box
duct collars shall not exceed 78.5 sq. in.
(1994 sq. mm) with a maximum of two duct collars per plenum. Duct collars shall be securely fastened to the
plenum surface. Any segment of the duct collar that protrudes inside the plenum wall must not interfere with the
damper blade operation.
4) The steel plenum box is to be attached to the damper using a #8 screws,
welds. Minimum of two per side (Figure 9).
5) The attachment of the screws or rivets must not interfere with the damper operation.
Fabrication of Fiberglass Ductboard Plenum for CRD-1WT
1) Fiberglass ductboard shall be a minimum of 1 inch (25 mm) thick UL 181 listed and have a minimum R-value 4.3.
2) The inside width x length dimensions on the duct board plenum shall be sized no greater than
than the damper frame. The maximum plenum height shall be 15 in. (381 mm) as illustrated below. The plenum
should be sized to provide a snug fit over the damper frame.
3) Edge and corner preparation shall be accordance with details shown (Figures 10 and 11). Plenum top shall be
fabricated and attached using similar method, S-AF and SF-AF (Figures 10 and 11).
4) Corner sealing tape shall be UL 181 listed and minimum of 2 inches (51 mm) wide.
5) The plenum duct collars shall be a minimum of 30 ga. (0.4 mm) galvanized steel. The total area of the plenum
box duct collars shall not exceed 113 sq. in. (2870 sq. mm) with a maximum of two duct collars per plenum. Duct
collars shall be securely fastened to the plenum duct board. Any segment of the duct collar that protrudes inside
the plenum must not interfere with the damper blade operation.
6) Plenum shall be attached to ceiling damper subframe using UL 181 listed tape (Figure 12).
7) Refer to Figure 4-7 for ceiling damper installation. The CRD-1WT ceiling is classified for use in specific wood
truss ceiling assemblies. See UL Fire Resistance Directory for floor/ceiling and roof/ceiling design numbers listed
on page 1.
6
CRD-1WT & CRD-2WT
14 in.
maximum
Insulation
Damper
Band
Frame
Damper with Insulation
Band and Steel Plenum
Assembly
* Note that not all dampers
with a steel plenum require
an insulation band.
Figure 9
⁄
in. (3 mm) rivets, spot welds, or tack
1
8
14 in.
maximum
Plaster
Flange
Damper
Frame
Damper without Insulation
Band and Steel Plenum
Assembly
⁄
in. (3 mm)larger than the
1
8
⁄
in. (3 mm) larger
1
8
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