Cfm And Duct Size

16 up to 11 40 el 12 to 15 55 el 16 to 21 75 el 22 to 27 100 el 28 to 33 125 el return air system no.

Cfm and duct size.

Without an adequate size duct a higher cfm blower will encounter too much air resistance to work effectively. Velocity decrease due to duct drag. Using your ductulator match each room s cfm requirement to your planned friction rate. Duct system sizes and airflow quick chart created date.

Duct and i expect that it is quite common for installations to use reducers when routing through cabinets and walls. Most hvac systems use a friction rate of 0 1 water column per 100 feet of duct. 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 6 6 100 125 10 x 4 6 x 6 7 125. 810 cold air boot collar duct 45 65 el air flow dynamics duct sizing reference guide supply or return duct size capacity 09 to 10 pressure drop per 100 el.

As you match each room s cfm to the ductulator it will give you the size of duct you need to run to the room. This equal friction method of duct sizing should be adequate for normal residential furnace heating and air conditioning applications. 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. Duct elbows square throat no.

V 2000 cfm 10 inches 1 12 ft inches 12 inches 1 12 ft inches 2400 ft min 12 2 m s the velocity in the the equivalent 12 inch circular duct according the table above is 2589 ft min 13 2 m s. The size of your ducting and your cfm go hand in hand. Most technicians are skeptical about these numbers especially on the return air side of the system. However higher cfm ratings require larger diameters of eight to 10 inches.

For older less powerful range hoods ducting sizes tend to be four to six inches in diameter. I notice my kitchen has a 4 dia. Perhaps you could expand your article to include any effects of reducing the duct size on the effective cfm ie.