How to Splice an HVAC Supply Line

Pull the clamping screw head away from the clamping body of a stainless steel flex clamp to pivot it to its open position. Slide the end of the clamp band in the clamping body. Push the screw down to lock it in place. Set up a second clamp using the same procedure.

Expose the first four inches of the inner of both pieces of flex entering the splice, by rolling the outer insulation cover back and tucking it below the outer sheathing. Slide one assembled stainless steel clamp over the exposed liner of each flex end.

Wipe the exterior surface of a 4-inch beaded galvanized sleeve with a rag. Ensure the ends are clear of dirt up to the edges of the bead. Apply an even coat of mastic sealant to the cleaned ends of the sleeve.

Slide the inner sleeve of each piece of flex over the galvanized sleeve. Ensure the ends of both pieces sit tight to the edges of the center bead of the sleeve. Push both stainless steel flex clamps toward the connection between the pieces of flex until they both sit one inch away from the sleeve bead. Tighten both clamping screws by turning their heads clockwise with a 5/16-inch nut driver.

Unroll the insulation from both ends of flex. Ensure both ends of insulation touch or overlap by one inch. Pull the outer sheathing over the insulation. Overlap the outer sheathing by one to two inches. Wrap duct tape over the exposed end of the outer sheathing to seal the connection from moisture.