How to Install HVAC Duct Spin-In Collars
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How to Install HVAC Duct Spin-In Collars

A guide for the homeowner looking to tap a new duct run to an existing system. This article covers both fiberglass and sheet metal ducts.

A spin-in duct collar creates an easily sealable duct connection in both sheet metal and fiberglass ducts. A duct installer usually runs the trunk duct line, the main duct run, from the air handling unit toward the furthest room. After running the trunk line, the installer runs the branch lines to each individual room. Round branch lines often tap into the trunk line with spin-in duct collars -- some duct systems use dove-tail collars. A spin-in collar accepts both flex duct and round sheet metal duct.

Installing Spin-In Duct Collars in Fiberglass Duct Board

Step 1) Place the discharge end of the spin-in collar against the trunk line or plenum. Use a marker to trace the outside of the collar. The intake end of the collar has the spin-in flange and the round duct will slip over the discharge end.

Step 2) Use a duct knife to cut the fiberglass duct board along the circle outline. Remove the cutout circle.

Step 3) Make a 1-inch-long slice into the duct board's exterior foil.

Step 4) Place the spin-in collar's intake flange over the hole in the duct board. Line up the spin-in flange's groove with the slice made in the foil. The spin-in blade acts as the collar's locking device and looks like a flexible strip of metal.

Step 5) Twist the spin-in collar clockwise until the spin-in flange has completely penetrated the interior of the duct board.

Step 6) Cover the spin-in collar's flange with duct sealing mastic. Use a brush to apply a coat completely around the outside of the connection. Many installers seal the spin-in collars after installing the round duct.

Installing Spin-In Duct Collars in Sheet Metal Duct

Step 1) Place the spin-in collar's discharge end against the side of the sheet metal HVAC duct. Use a marker to trace the outside of the collar. A sheet metal spin-in collar has a U-shaped groove around its intake end.

Step 2) Place a flat screwdriver's blade against the sheet metal duct's surface. Position the blade 1-inch inside of the circle outline's edge. Strike the screwdriver's blade with a hammer until the blade cuts into the sheet metal. Create a 1-inch slice in the sheet metal. This slice must go towards the center to avoid damaging the metal on the outside of the circle.

Step 3) Place the blade of a pair of tin snips in the slice. Cut out the circle. To avoid making burrs in the sheet metal duct, avoid closing the blades completely between strokes. If the snip's blades close completely, the blade's tips notch the sheet metal, creating the burr.

Step 4) Hold the tin snips against the edge of the circle cutout. Make a 1/4-inch-long notch in the sheet metal duct.

Step 5) Place the spin-on duct collar's lip, the lip found in the U-shaped groove, against the notch in the duct. Spin the collar clockwise one full turn. The U-shaped notch will slide along the edge of the circle cutout. The U-shaped notch will lock the spin-in collar against the sheet metal duct's surface.

Step 6) Seal the spin-in duct collar to the sheet metal duct with duct sealing mastic. Use a brush to apply the mastic.

Remodeling and air-conditioning contractors often add new duct runs to an existing system. A spin-in collar allows the contractor to tap into the duct fairly easily. Some spin-in duct collars come with damper blades. If using a spin-in collar with a damper blade, position the blade's handle in a convenient location, usually a vertical position works best.

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Comments (5)

Very informative step-by-step instructions and nicely executed. too. Thanks for sharing Voted up

Great, informative and educational article.....thanks for sharing

Very great discussion on this topic.

Precise step by step DIY instructions well presented.

A perfect and well constructed "how to"