Size, Pressure & Special Routing · Size, Pressure & Special Routing
Narrow rectangular branch under 12 inches high
Low-profile branch
ConnectionS-drive/TDC
SupportWide strap/trapeze
Before you start
- Confirm shallow branch dimensions, fitting geometry, joint profile, reinforcement, support width, and route clearance.
- Inspect the narrow duct for bowed faces, crushed ends, and blocked opening.
- Verify fittings do not choke the already shallow airway.
- Plan low-profile joints and broad support.
Tools and materials
Shallow rectangular duct and fittings, approved low-profile S-drive or TDC components, gasket, cleats, fasteners, sealant, broad straps or trapezes, level, and clamps.
Lay it out
- Set the bottom and top planes.
- Check every elbow, tap, and transition for internal clearance.
- Keep supports clear of the shallow joint.
Set and support it
- Use wide support across the duct width.
- Prevent crushing during lifting.
- Support fittings near direction changes.
Make the connection
- 1
Align both shallow sections without bowing them.
- 2
Install gasket and mechanical joint components.
- 3
Clamp square before fastening.
- 4
Complete the low-profile joint.
- 5
Seal after mechanical connection.
- 6
Load the broad support.
- 7
Inspect the internal opening.
Check the install
- The opening remains full and unobstructed.
- The duct is not bowed or crushed.
- Joints are square.
- Supports spread load across the width.
- Fitting geometry does not choke flow.
Common mistakes
- Using tall internal hardware in a shallow duct.
- Crushing the duct with narrow strap.
- Forcing a bowed face flat at the joint.
- Using a fitting that narrows the opening.
Stop and ask
Stop if fitting geometry, joint hardware, reinforcement, or support reduces the usable opening or crushes the shallow duct.