How many cfm in a 6 inch duct

Charts are useless without context. Not even getting into equivalent length and fittings, etc. Please add some context for the assumptions of these values. Hello there, these are standard values HVAC technicians use. We will try to give some context as recommended, thank you.

The unintended results of these traditions are HVAC systems that fail to perform at their anticipated levels. How can you help them understand a 6-inch duct might not always deliver cfm? The 0. The reason setting your duct calculator to 0. A lot of confusion begins here, as many believe this is the design pressure they need to use.

The recommended residential setting on a slide duct calculator is for equivalent feet of duct. This is the amount of straight duct a duct fitting is equivalent to. In other words, equivalent feet of duct can easily be used up in a single degree elbow with a square throat, round heel, and no turning vanes. Think about that — a single duct elbow with a square throat, round heel, and no turning vanes would be the same as feet of straight duct of the same size.

Depending on the complexity of the duct system, you could easily end up with more than feet of equivalent duct before you know it. The passion is the same among these individuals, but the design numbers used are all over the place. A variety of values are used that range from 0. Which design rate is the correct one, and who is correct? Sadly, the truth about how any of these duct system designs perform is completely unknown in most cases.

With this being a common occurrence, is it any wonder there is so much division about which duct-sizing method should be used? Have a question? Contact Product Support.

Call Products Have a question? If you want to get a brawl started among HVAC contractors, start a discussion on duct sizing. There is a passion among those in the HVAC industry for the methods they use for sizing ducts.

These methods are typically traditions passed down over decades. If you question the duct sizing method, you question something that dad or even granddad taught them as the truth.

You might as well spit in their face in many cases. The unintended result of this tradition is HVAC systems that fail to perform at their anticipated levels. With this being such a large problem, how do you help someone understand that the duct design methods they have used for years might not be working like they assume? I had to deal with something similar to this problem years ago in regards to self-balancing duct systems.