Slip-In Mounting vs Flanged

The installation of electric duct heaters can take one of two forms – flanged or slip-in mounting. If you are trying to compare and contrast slip-in vs flanged the following article will give you the basics.

Existing Ducts

For retrofits into existing ducts, flanged mounting like that available on the INDEECO QUZ model is usually preferred. With proper planning and care, a cut of the appropriate width can be made in the older ductwork with enough metal left over to form four flanges. These flanges are bent into place around the perimeter of the duct on both sides of the cut. The heater is then mounted to the flanges using bolts or sheet metal screws. If necessary, for larger heaters, additional bracing can be installed.

New Construction

For new construction, however, a hole is simply cut in the side of the duct and the heater simply slid into the pre-fabbed hole. Sheet metal screws again hold the heater in place with additional bracing used as required. The latter process can also be applied to fiberglass ducts provided a sheet metal liner – extended in to the duct at least 6″ on both sides of the heating elements – is used to protect the fiberglass material. In particular, the INDEECO QUA model is an excellent slip-in option in these cases – especially for open coil applications. Finally, either of these electric duct heater options can be custom-built for any size duct and for any unusual placement or installation.

For more information about the installation of our electric duct heaters – flange or slip-in mounting – please visit us online at or call us directly at 800-243-8162.


Need a quote?

We market our products through a nationwide network of representatives. Contact us today!

Scroll to Top