Duct Sizing Hvac Cfm Chart

To insure proper distribution of air volume dampers must be used for all branch runs.

Duct sizing hvac cfm chart.

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. The chart should not be used to design complete duct systems. The chart is based on metal 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.

Note also the return air grille sizing formula at the top of the chart. 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. Larger volumes or higher static pressures should be dealt with on an individual job basis. 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.

For the same 2 5 ton system with a filter grille the grille size would need to be what size asked rick we usually use a 20 x 20 for 2 5 ton said the tech 20 x 20 x 2 800 800 cfm well that s big enough for a 2 ton but a 20 x 25 may be a better choice. If a room is 250 square feet the result will be a duct size of 8 inch round. Calculate the duct size by using a duct calculator.