Flex Duct Hvac Cfm Chart

For instance a 2 5 ton system approximately 400 cfm per ton would require 2 14 flexible return ducts or 1 very short flexible 18 duct to move the 1000 cfm required by the 2 5 ton system.

Flex duct hvac cfm chart.

Friction rate velocity friction rate. Use the online duct calculator see references and calculate the needed flex duct size. 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. Select the duct type on the pull down menu.

Read friction loss inches of water and duct velocity fpm. Read duct diameter inches and duct velocity fpm. Enter round duct diameter inches duct airflow cfm duct length and the number of bends. Calculations are for 60 f dry air at sea level from 5 to 3000 cfm approximately standard air which is 0 075lb da ft.

Based on duct diameter. As systems increase in efficiency the tolerances of how we have always done it will no longer be adequate. Input the required cfm in the box below that. Air volume equivalent round air volume cfm 4 6 8 10 12 duct inches cfm 50 6 x 4 550 75 6 x 4 675 100 8 x 4 6 x.

Rectangular duct is rounded up to the nearest 1 4 inch. Sheet metal duct friction loss calculator. Click calculate and you will see the size of flex duct you need for that room. Cfm 4 cfm 6 cfm 8 cfm 10 cfm 12 60 6x4 60 4x6 90 4x8 120 4x10 150 4x12.

This equal friction method of duct sizing should be adequate for normal residential furnace heating and air conditioning applications. Metal ductboard flex size by. Larger volumes or higher static pressures should be dealt with on an individual job basis. Enter the desired length of the rectangular duct.

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 duct size. Enter duct airflow cfm duct velocity fpm duct length and the number of bends. Enter round duct diameter. If ashrae 2013 is selected flexible roughness is 0 003 ft when straight and fully stretched tight at 0 compression adjusted at other compressions otherwise the.

In wg duct tel. The flex duct size may be different than the hard duct that runs to that room.