Flexduct 1840 Rip Stop Flex Duct 18 in 25 Ft R4.2

Product Description

The FLEXDUCT 1840 is an 18-inch inside diameter, 25-foot rip stop insulated flexible duct designed for residential and commercial HVAC air distribution systems. Built to the 40 Series specification, it uses a tri-layer construction of polyester, fiberglass, and metalized polyester to deliver R4.2 thermal insulation and a vapor transmission rate of 0.05 or less. The duct supports airflow up to 6000 feet per minute (fpm), making it suitable for high-volume trunk and branch runs. The silver metalized outer jacket resists moisture and maintains jacket integrity under normal mechanical handling. Licensed HVAC technicians and sheet metal mechanics are the primary installers of this product.

The FLEXDUCT 1840 is used in forced-air heating and cooling systems where large-diameter flexible duct runs are required. Its 18-inch bore accommodates high-capacity air handlers and rooftop units rated up to approximately 15 tons. Typical installations include runs from plenum boxes to large diffusers, bypass ducts, and return-air connections in commercial light construction, large residential applications, and equipment rooms. The rip stop inner core resists tearing during installation routing through tight spaces or over structural obstacles.

Key Features

• 18-inch inside diameter supports high-volume airflow up to 6000 fpm, rated for approximately 15-ton systems
• R4.2 fiberglass insulation blanket reduces thermal losses along the duct run
• Vapor transmission rate of 0.05 or less minimizes condensation risk on the duct exterior
• Rip stop inner liner construction resists tearing and puncture during installation
• Pressure rating of -0.5 to 10 inches water column covers both supply and return applications
• Temperature rated from -20 degrees F to 180 degrees F for use in unconditioned attics, crawlspaces, and mechanical rooms
• Domestic manufacture with silver metalized polyester outer jacket

Compatibility

Designed as an OEM-style replacement or new-installation flexible duct for forced-air HVAC systems requiring an 18-inch inside diameter connection. Suitable for supply and return applications on air handlers and rooftop units in the 40 Series flexible duct category.

Installation Notes

Installation should be performed by a licensed HVAC technician or sheet metal mechanic in accordance with SMACNA flexible duct installation standards and local mechanical codes. Power down the air handling unit and lock out the disconnect before making duct connections. Avoid sharp bends that exceed the minimum bend radius of the duct, as compressed or kinked sections significantly increase static pressure and reduce airflow. Secure both ends with approved draw bands or clamps and seal with mastic or listed duct tape per code requirements.

Technical Specifications

• Inside Diameter: 18 inches
• Length: 25 feet
• Flow Rate: 6000 fpm (approximately 15 ton capacity)
• Insulation Value: R4.2
• Pressure Rating: -0.5 to 10 inches water column
• Temperature Rating: -20 degrees F to 180 degrees F
• Vapor Transmission: 0.05 or less
• Material: Polyester, Fiberglass, Metalized Polyester
• Finish: Silver
• Series: 40 Series
• Type: Rip Stop Insulated
• Package Dimensions: 31 inches L x 23 inches W x 31 inches H
• Weight: 31.53 pounds
• Origin: Domestic

Standard Information

• Brand: FLEXDUCT
• Manufacturer Part Number: 1840