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Furnace Transition to Duct Work Sealing?

We have a forced air furnace. The "collar" that transitions the furnace to the duct work is flexible (due to the expanding soils in Colorado). The collar has some holes in it. I have used duct tape to seal the holes, but it doesn't stand up to the heat. What else can I use?
I would appreciate any ideas or product suggestions.

Re: Furnace Transition to Duct Work Sealing?


Check the Yellow Pages under "Furnaces-Supplies & Parts" or "Sheet Metal Products", or "Heating Equipment Parts-Wholesale"

They carry Aluminum Foil Tape in 60 ft. rolls rated at 275 degrees for approx $15, or Metalized Duct Tape in 60 yd rolls rated at 200 degrees for $7-10.

You can also buy a tube of High Temp caulking compound (metal standard caulking applicator needed) for $10 with which you can attach heavy duty aluminum foil to holes in Plenum or ducts.

Thin pieces of duct sheet metal (Home Depot/Lowe's) can be cut to shape with a sheet metal shears; small holes drilled, & easily attached to flex plenum/duct with self-tapping sheet metal screws.

The entire piece of plenum flexduct can be removed & replaced with a new piece, available at the above wholesale dealers---many wholesale dealers will sell to homeowners, either on the web or in your local town, often at wholesale prices---known as a "cash sale".

Google "Plenum flexduct", or "flexible duct installation", or "metal heating duct products" or "flexible heating duct products" to get a ballpark price range for these products.

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