Seal-tite 92RFB-212220 Furnace Return Air Support Box

Product Description

The SEAL-TITE 92RFB-212220 is a furnace return air support box designed to provide a stable, sealed plenum transition at the base of a residential gas or electric furnace. This unit measures 21.375 inches wide by 22.1875 inches deep by 20 inches tall, making it suited for full-size upflow or downflow furnace installations where a properly sized return air cavity is required beneath or adjacent to the unit. HVAC technicians install this box to maintain negative-pressure integrity on the return side of the air handler, reducing air leakage and supporting efficient system operation.

This return air support box is intended for residential HVAC installations where the furnace requires a dedicated support and return air plenum assembly. It is typically installed during new construction or furnace changeout projects where the existing return air infrastructure does not match the replacement unit footprint. The 20-inch height accommodates standard platform or closet furnace installations, and the external dimensions are designed to align with common furnace cabinet widths in the 21 to 22-inch range.

Key Features

• Dimensions of 21.375 inches x 22.1875 inches x 20 inches match common full-size residential furnace footprints
• Functions as both a structural support platform and a sealed return air plenum
• Designed for upflow or platform-mount furnace installations
• Supports negative-pressure return air integrity to reduce bypass leakage
• Sized for use in closet, alcove, or utility room furnace installations

Compatibility

Designed as an OEM-style return air support box for residential gas and electric furnaces requiring a platform plenum with approximate external dimensions of 21.375 inches x 22.1875 inches x 20 inches. Verify cabinet width and return air opening dimensions against the furnace manufacturer specifications before installation.

Installation Notes

A licensed HVAC technician should install this component in accordance with local mechanical codes and manufacturer guidelines. Disconnect power to the furnace and, if applicable, shut off the gas supply before beginning any plenum or return air work. Ensure all joints between the support box and the furnace cabinet are sealed with approved HVAC mastic or metal-foil tape to maintain system pressure balance. Do not modify the structural dimensions of the box, as doing so may compromise both support integrity and return air sealing.

Technical Specifications

• Width: 21.375 inches
• Depth: 22.1875 inches
• Height: 20 inches

Standard Information

• Brand: SEAL-TITE
• Manufacturer Part Number: 92RFB-212220