Convert rectangular duct to round equivalent.
Round duct duct sizing chart cfm.
Include fittings in the duct tel enter either.
The table below can be used to compare equivalent diameters for rectangular and round circular ducts.
Larger volumes or higher static pressures should be dealt with on an individual job basis.
This equal friction method of duct sizing should be adequate for normal residential furnace heating and air conditioning applications.
Flex duct has a higher pressure drop and as such may require the size shown on this guide be increased by 1 round size for up to 800 cfm and 2 round sizes above 800 cfm to insure proper airflow.
The rectangular dimensions and the air flow volume are adapted to the equal friction loss.
In wg duct tel.
Failure to do so will result in high velocity and very likely loss of airflow.
The table is based on the ducts friction loss formula.
Duct system sizes and airflow quick chart created date.
Velocity duct sizing chart residential main supply trunk ducts non zoned systems target velocity of 800fpm used listed by air quantity round duct size and nearest square duct size 500cfm 11 ø or 10 x 10 1 300cfm 16 ø or 14 x 16 600cfm 12 ø or 10 x 12 1 400cfm 18 ø or 16 x 16.
While a duct sizing calculator built for a specific type of ductwork is the best possible method for sizing ducts the attached chart can be used in most single story homes with a centrally located unit and reasonable length duct runs.
Flex duct 05 on most metal duct calculator round metal pipe 06 on most metal duct calculators field duct sizing chart rectangular sheet metal duct 07 on most metal duct calculators step one identify the volume of air that will be passing through the duct step two select the duct size from the table that can carry that volume of.
Friction rate velocity friction rate.
Design cfm 4 cfm 6 cfm 8 cfm 10 cfm 12 60 6x4 60 4x6 90 4x8 120 4x10 150 4x12 90 8x4 110 6x6 160 6x8 215 6x10 270 6x12 120 10x4 160 8x6 230 8x8 310 8x10 400 8x12 150 12x4 215 10x6 310 10x8 430 10x10 550 10x12 180 14x4 270 12x6 400 12x8 550 12x10 680 12x12 210 16x4 320 14x6 490 14x8 670 14x10 800 14x12 240 18x4 375 16x6 580 16x8 800 16x10 950 16x12 270 20x4 430 18x6 670 18x8 930 18x10 1100.
Sheet metal duct friction loss calculator.
Read round duct diameter inches and friction loss per 100 of duct inches of water.
Convert diameter to rectangular equivalent.
The equivalent diameter is the diameter of a circular duct or pipe that gives the same pressure loss as an equivalent rectangular duct or pipe.
The chart is based on metal duct.
