Sealing Boxes/Boots/Cans

Today's tech tip 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, 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. That way, it will seal against leaks to and from the unconditioned space as it presses against the substrate. 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 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 grilles and properly sealing them. As you can see, this return grill that I have pulled down was not properly sealed. Not siliconed or masticed, so basically what's happening—you can see a little bit of wood here. When the blower comes on, it pulls air—it'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. So, 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.

Related Tech Tips

Refrigeration Without Refrigerant
We just wrote about rejecting heat to the atmosphere via radiant cooling. That’s one example of cooling without refrigerants, but there are quite a few others out there. In this article, we’ll look at some other cooling methods that don’t use refrigerants. Vortex tubes Vortex tubes swirl gas in a chamber, separating it into hot […]
Read more
Ball Bearing vs. Sleeve Bearing Motors
One aspect of motor selection that can get overlooked is motor bearings, and it can have big consequences. Sleeve bearings are most common in residential and light commercial applications because they are less expensive and quieter. They don't have rolling “balls” but rather rely on a thin film of oil on metal sleeves. Sleeve bearings […]
Read more
UV Lights
A quick note about UV lights: they work like sunlight in that they prevent and kill many types of bacteria and fungi when exposed to the light on surfaces. They do not generally do a great job of killing spores suspended in the air stream. UV lights are great at killing yucky stuff on surfaces […]
Read more

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

loading

To continue you need to agree to our terms.

The HVAC School site, podcast and daily tech tips
Made possible by Generous support from