Air Flow Products 77F182020 Transition Boot Flange 18x20

Product Description

The AIR FLOW PRODUCTS 77F182020 is a straight transition boot with flange, designed to connect square or rectangular duct openings to round collars in forced-air HVAC systems. The 77F series boot transitions an 18x20 inch rectangular opening down to a 20-inch round collar, making it a practical fitting for supply or return air trunk-to-branch connections. This type of fitting is installed by licensed HVAC technicians and sheet metal mechanics during new construction, system retrofits, and ductwork modifications where a square-to-round transition is required.

This transition boot is suited for residential and light commercial forced-air applications where trunk lines must step down to branch runs or collar tie-ins. The flanged design simplifies connection to plenums, air handlers, or rectangular duct sections, and the straight profile keeps the fitting compact in tight ceiling or floor cavity installations. Installers working on supply-side distribution systems will find the 18x20 inlet and 20-inch collar dimensions appropriate for medium-to-large air handler configurations.

Key Features

• Square-to-round geometry transitions an 18x20 inch rectangular duct opening to a 20-inch round collar
• Integrated flange provides a secure mounting surface for connection to plenums or rectangular duct sections
• Straight profile minimizes depth requirements in confined ceiling, floor, or wall cavities
• 77F series design engineered for consistent fitment in forced-air duct systems
• Suitable for supply and return air applications in residential and light commercial systems

Compatibility

Designed as an OEM-style sheet metal transition fitting for use in standard forced-air HVAC ductwork systems requiring a square-to-round transition at an 18x20 inch rectangular opening with a 20-inch round collar outlet.

Installation Notes

Installation should be performed by a qualified HVAC technician or licensed sheet metal mechanic in accordance with applicable mechanical codes. Power down and lock out the air handling unit before beginning any ductwork modification. Seal all joints with listed duct sealant or approved foil tape per SMACNA guidelines to prevent air leakage. Support the fitting per local mechanical code requirements to avoid stress on adjacent duct connections.

Technical Specifications

• Inlet Size: 18x20 inches
• Collar Diameter: 20 inches
• Transition Type: Square to Round
• Profile: Straight
• Flange: Yes
• Series: 77F

Standard Information

• Brand: AIR FLOW PRODUCTS
• Manufacturer Part Number: 77F182020