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INSPECTION & INSTALLATION
4.7.3 Installation Instruction for Air Ducts and Air Connectors - Metallic with Plain Ends
Connections and Splices - Using Tape or Mastic and Sheet Metal Screws
1. After cutting duct to desired length, fold back jacket and insulation exposing core. Trim core ends squarely using suitable metal shears. Determine optional sealing method (Steps 2 or 5) before proceeding.
4. Secure to collar/sleeve using #8 sheet metal screws spaced equally around circumference. Use 3 screws for diameters under 12" [300 mm] and 5 screws for diameters 12" [300 mm] and over.
2. When mastics are required and for pressures 4" w.g. [1000 Pa] and over, seal joint with mastic applied uniformly to the outside surface of collar/sleeve. (Disregard this step when not using mastics and pro- ceed to Step 3).
5. For pressures under 4" w.g. [1000 Pa] seal joint using 2 wraps of duct tape applied over screw heads and spirally lapping tape to collar/sleeve. (Disregard this step when using mastics per Step 2).
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3. Slide at least 1" [25 mm] of core over metal collar for attaching duct to take off or over ends of a 4" [100 mm] metal sleeve for splicing 2 lengths of duct.
6. Pull jacket and insulation back over core. Tape jacket with 2 wraps of duct tape. A clamp may be used in place of or in combination with the duct tape.
NOTES: 1. For uninsulated air ducts and air connectors, disregard references to insulation and jacket. 2. Use mastics listed and labeled to Standard UL 181B and marked ”181 B - M ” on container. 3. Use tapes listed and labeled to Standard UL 181B and marked “181 B - FX ”. 4. Nonmetallic clamps shall be listed and labeled in accordance with Standard UL 181B and marked “181 B - C ”.
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