Hey Ed, Is There a Way to Size a Duct Without Calculating a Friction Rate?

In This Edition of “Hey Ed,” Ed Discusses if There Is a Way to Size a Duct Without Calculating a Friction Rate

Hey Ed, is there a way to size a duct without calculating a friction rate? There can be, and first and foremost, I'm always going to recommend people follow the guidance in Manual D® when it comes to sizing a duct. But sizing a duct based off of your velocity is not a bad process, as long as we ensure we have enough starting pressure to begin with. This falls right in line with, you can read guidance that talks about using random friction rates like point 1 or .08 or .05, they will give us a duct with enough internal area so that we can have air passing through them at a reasonable velocity, but using those made-up friction rates does not give us any assurance that we have enough fan power to begin with. And that's why I will always recommend following the guidance in Manual D® and populating the friction rate worksheet, and that's the way I see it.