CFM reduction using 8"x7" reducer

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CFM reduction using 8"x7" reducer

Postby RunningLow » Fri Jul 17, 2015 3:42 pm

1) Roughly, how much CFM loss by reducing 8" flex duct to 7" connection at the register boot (12 x 6)? Quite a bit, or barely noticeable?

The duct connects to boot at about 60 - 70 deg angle (not full 90).

Replacing the old 7" duct with 8" to increase CFMs to a warmer room.

Wonder if replacing the boot w/ one for 8" duct is worth it? Can probably get the old boot out - w/o tearing up sheet rock.

2) How much will a * 14 x 6 * x 8" connection, insulated boot increase CFM, vs. a 12 x 6 x 8?
If very little, there'd be no reason to make 14 x 6, with same 6", 7", 8" duct size as a 12x6 box?

Either size, I'll * replace * the restrictive register - 3 way, fixed fin (that's more for ceiling), w/ a sidewall 2 way, or one w/ straight, adjustable fins. It's on a wall, 8 ft off floor.

Thanks.
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- CFM reduction using 8"x7" reducer

Postby Freon » Fri Jul 17, 2015 7:27 pm

Google "7" duct cfm" You will see many sites with the data (pdf) you seek.
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