Hey Ed, Do You Like Your Ducts Kinky?

In This Edition of “Hey Ed,” Ed Discusses if He Likes His Ducts Kinky

Hey Ed, do you like your ducts kinky? I'm a kinky kind of guy at times, especially when I don't need as much airflow. Are there going to be times where I intentionally install ducts with more sag than Manual D® recommends? You betcha. If you're following the guidance in Manual D®, you're going to find that our duct is not supposed to have more than four percent sag. If you want to really get in the weeds with this, we're talking about a 10-foot piece of duct, flex duct that is, that's spanning 9.6 feet. That's going to give you four percent sag. The guidance in Manual D® with any of our duct sizing selection is based off of a duct with no more than four percent sag. You can find other guidance from other entities that will show, for instance, a ten-foot duct with a seven-foot span, that's going to be 30% compression or sag. Mathematically, that could, depending on our friction rate, could require the same volume of air going up two sizes in ducts. What if I have some leftover six-inch and I only need 40 or 50 CFM? Can I purposely have that extra kink? Absolutely. Nothing wrong with doing that. As long as it's mathematically calculated and not just made up. And that's the way I see it.

In This Edition of “Hey Ed,” Ed Discusses if He Likes His Ducts Kinky