Flex Duct Cfm Ratings Chart

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

Flex duct cfm ratings 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. Humidity 400 cfm ton shr above 85 17º td low humidity 450 cfm ton cfm total heat equation cfm btu hr 4 5 x h x acf sensible load 1 08 x td x acf friction rate used in duct calculators friction rate pressure drop is the available static pressure asp allocated to the duct work. Input the required cfm in the box below that. Digitalplumber is just a name for use here i am not a plumber.

As systems increase in efficiency the tolerances of how we have always done it will no longer be adequate. On a slide rule duct calculator i have it states that a 9 inch flex duct is rated at about 205. Click calculate and you will see the size of flex duct you need for that room. 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.

Duct system sizes and airflow quick chart created date. 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 air step three if desired airflow exceeds the cfm rating increase to the next duct size. Use the online duct calculator see references and calculate the needed flex duct size. Failure to do so will result in high velocity and very likely loss of airflow.

This equal friction method of duct sizing should be adequate for normal residential furnace heating and air conditioning applications. Select the duct type on the pull down menu. In the following chart. Shr 80 to 85 19º td ave.

The chart is based on metal duct.