Sealing Boxes / Boots / Cans

August 5, 2019 Bryan Orr No Comments

The tech tip today is a video put out by my friend Brad Hicks from the HVAC in SC YouTube Channel. Thanks Brad!

Seal boots to prevent raccoon leaks

Ok, so this has nothing to do with raccoons but I like that photo.

Whenever you are installing duct boxes (also called boots or cans) in an aftermarket application, make sure to place a bead of sealant like mastic or silicone on the flange so that as it presses against the substrate it will seal against leaks to and from the unconditioned space. When installing in a new construction environment where the boxes / boots / cans go in before the substrate you will either want to use boots that already have gaskets or you will want to add a gasket to the flange such as foam tape. In these cases, it is still a good idea to seal the edge further from the inside once the drywall (or similar) is in place and before the grilles and registers are installed.

Video Transcript

What’s going on guys? here’s another 60-second tech tip, this is on supply and return grills and properly sealing them. As you can see this return grill that I have pulled down was not properly sealed. No silicone or mastic, so basically what’s happening you can see a little bit of wood here when the blower comes on it pulls air that’s pulling unconditioned air from between the sheetrock and the wood that’s framing this box out of the attic and into our Airstream. Since our air filter goes here as well most of this isn’t being filtered, it’s just passing right into the system. As you can see that return is fairly dirty so all of this should be sealed with mastic and usually we just silicone or you can mastic this as well. Same thing with supply grilles, so if you ever have customers that are dealing with dust issues or units getting dirty but the filters aren’t that dirty this could be your culprit. Make sure you’re paying attention to the supplier return grilles and look out for this kind of stuff so hope that helps thanks for watching.