What Is a Duct Collar?

Purpose

• The primary purpose of the duct collar or start collar, as it is sometimes called, is to allow you to connect a round duct to a flat air return duct. The way that the collars are shaped, one end remains rounded and fits into the end of an existing rounded duct. The air return plenum that it is connected to usually has a flat surface. The other end of the collar accommodates the flatness by consisting of a ring of tabs that can be bent flat and connected to a hole cut into the flat surface.

Installation

• Installation of the air duct collar involves cutting a hole that corresponds to the diameter of the duct collar itself. The tabs on the connecting end are then bent outward to a 90-degree angle using every other tab. The straight tabs are inserted into the hole and the bent backward to hold the duct collar in place. The duct collar is held in place by sheet metal screws and a duct sealant.

Troubleshooting

• The area around the outside of the collar must be free from debris and other corrosion in order to connect the collar and seal it correctly. If you have any air leakage occurring around the duct, you will have an issue with the surface connection of the duct and the extent to which it is sealed. This generally requires that you pull off the existing duct collar and attempt to reseal it.

Types

• Other types of duct collars exist and can provide you with an installation that might be easier for your own particular situation. For instance, super seal start collars offer an alternative to the tabbed collars because they come with an attached gasket that is self-sealing. These can generally be placed over the hole and then allowed to self-seal to the existing duct work.