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Field Installation of Steel Plenums
1. The steel plenum box shall be a minimum of 28 ga.
(0.47mm) of galvanized steel.
2. The inside width x length dimensions of the steel
plenum shall be sized no greater than 1/8 in. (3mm)
larger than the damper frame. The maximum ple-
num height shall be 14 in. (356mm) 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. (.39mm) 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
®
Figure 5: Grille Mount with Duct Board Plenum
Figure 6: Duct Mount with Steel Plenum
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Figure 7: Duct Mount with Duct Board Plenum
1. Damper
2. Mounting Angle
3. Plaster Flange
4. Gypsum Board
5. Duct
6. Duct Retaining Angle
7. RC Channel
8. Duct Board Plenum
Note: Trim duct board to install mounting
angle. It is not necessary to re-install
trimmed piece to maintain UL certification.
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, 1/8 in. (3mm) rivets,
spot welds or tack welds. Minimum of two per side
(Figure 8).
5. The attachment of the screws or rivets must not
interfere with damper operation.
1. Damper
2. Mounting Angle
3. Plaster Flange
4. Gypsum Board
5. Grille
6. RC Channel
7. Duct Board Plenum
1. Damper
2. Mounting Angle
3. Plaster Flange
4. Gypsum Board
5. Duct
6. Duct Retaining Angle
7. RC Channel
8. Steel Plenum
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