Air Flow Products 77F182018 Transition Boot 18x20 18 in

Product Description

The AIR FLOW PRODUCTS 77F182018 is a straight transition boot with flange, designed to connect square or rectangular ductwork to round collar duct runs in residential and light commercial HVAC systems. This square-to-round fitting features an 18x20 inch rectangular opening and an 18 inch round collar, making it a practical solution for transitioning between differing duct geometries at air handlers, plenums, and trunk line connections. The integrated flange simplifies attachment to ceiling, floor, or sidewall framing during rough-in and finish duct work. HVAC sheet metal installers and mechanical contractors are the primary trades for this fitting.

This transition boot is suited for forced-air HVAC installations where a square or rectangular plenum or trunk must reduce or transition into an 18 inch round duct. Common applications include main trunk takeoffs, air handler discharge connections, and register boot installations in both new construction and retrofit projects. The straight profile allows direct, in-line installation without offsetting the airflow path, which helps maintain system static pressure and minimize turbulence at the transition point.

Key Features

• Square-to-round geometry transitions an 18x20 inch rectangular opening to an 18 inch round collar
• Integrated flange provides a secure mounting surface for attachment to framing or duct board
• Straight profile maintains in-line airflow for reduced turbulence and stable static pressure
• Designed for use at plenums, trunk lines, and air handler connections in forced-air systems

Compatibility

Designed as an OEM-style sheet metal transition fitting for 18 inch round duct systems connected to 18x20 inch rectangular duct or plenum openings in residential and light commercial forced-air HVAC applications.

Installation Notes

Installation is typically performed by licensed HVAC technicians or sheet metal mechanics in accordance with SMACNA duct construction standards and local mechanical codes. Power down the air handling unit and close the system disconnect before beginning duct work. Secure the flange to framing using appropriate sheet metal screws, and seal all joints with listed duct sealant or UL 181-rated tape to prevent air leakage. Do not compress or distort the collar during installation, as deformation can restrict airflow and affect system performance.

Technical Specifications

• Configuration: Straight Transition Boot with Flange
• Shape Transition: Square to Round
• Rectangular Opening: 18x20 inches
• Round Collar Diameter: 18 inches

Standard Information

• Brand: AIR FLOW PRODUCTS
• Manufacturer Part Number: 77F182018