Thermaflex 54704000002 Flex-vent Insulated Flex Duct 4in 25ft R4.2

Product Description

The THERMAFLEX 54704000002 is an insulated flexible air duct from the Flex-Vent KP Series, designed for residential and light commercial HVAC distribution systems. This duct measures 4 inches in diameter and comes in a 25-foot length, making it suitable for branch runs from a plenum or trunk line to diffusers and registers. The R4.2 insulation value helps limit heat gain and loss across the duct run. It carries a 5,000 feet-per-minute velocity rating and is rated for operating temperatures from -20 degrees F to 250 degrees F. The inner core and jacket are constructed of polyester and steel. Domestic HVAC contractors and sheet metal mechanics are the primary installers.

This flexible duct is used in forced-air heating and cooling systems where a semi-rigid or hard-pipe run is impractical. Typical applications include connecting supply boots to trunk lines in residential attics, crawlspaces, and dropped ceilings, as well as light commercial VAV box connections. The 10 inch-WG positive and 0.5 inch-WG negative pressure ratings accommodate standard residential blower pressures without collapse or blow-out. The black outer jacket and polyester-steel construction handle the temperature swings common in unconditioned attic installations. A vapor transmission rating of 0.1 perm limits moisture migration through the duct wall in humid climates.

Key Features

• 4-inch diameter, 25-foot length for branch-run supply applications
• R4.2 insulation value reduces heat transfer across the duct wall
• 5,000 fpm velocity rating supports standard residential and light commercial blower outputs
• 10 inch-WG positive pressure and 0.5 inch-WG negative pressure rated
• Operating range of -20 degrees F to 250 degrees F suits unconditioned attic and crawlspace installs
• 0.1 perm vapor transmission rating for moisture control in humid environments

Compatibility

Designed as an OEM-style flexible duct replacement or new-installation component for 4-inch supply branch runs in residential and light commercial forced-air HVAC systems.

Installation Notes

Flexible duct installation is typically performed by licensed HVAC contractors or sheet metal mechanics in accordance with SMACNA flexible duct performance and installation standards. Power down and lock out the air handler before connecting or disconnecting duct sections. Limit bends to maintain the duct as straight and fully extended as possible, as sharp bends and compression significantly increase static pressure drop. Secure all connections with approved clamps or ties and seal with mastic or listed tape per local mechanical code requirements.