Hvac Return Duct Size

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Hvac return duct size. You have only 364 sq. Houses often have two or more return collecting points each with a filter which join before re entering the heating unit. Nominal size in x in approximately capacity cfm 10 x 4. Round ducting comes in standard sizes ranging from 4 9 inches in diameter to just over 41 inches in diameter with sizing also depending on airflow needs per cubic foot per minute and velocity.

There usually are fewer return vents but they are much larger. An hvac return air can be in the floor but they work much better on walls up about 7 feet. Use the following formulas. Step 5 divide the cmf per vent by the total amount of cmf for your furnace.

You need close to 600 sq. A typical supply vent is 4 by 10 to 12 inches and a typical return vent is 16 by 20 inches or larger. Calculate the size of your ducts vents by multiplying the length by the width. 4 tons x 144 square inches return air duct in square inches.

For example if the vents are 5 by 10 inches the total cmf for the vents is 50 cmf per vent. 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. Your return ducts are just right but the return grills are way to small. A mismatch in return air inlet grille or duct size will reduce the system s effectiveness.

Calculate the return duct size based on the air conditioner s size and the type of duct you are using. Most technicians are skeptical about these numbers especially on the return air side of the system. Size of air conditioner example.