Hvac Return Air Duct Size

The furnace s british thermal units btus will help calculate the size it needs.

Hvac return air duct size.

Dampers on take off duct runs allow for adjustments of air distribution. In order to maintain velocity reduce duct size. I have two return ducts hard metal round one 14 inch and one 12 inch. Return air cfm must be equal or greater than supply air cfm.

Have to get the air back to the furnace. How do i calculate if the return ducts are too small too. Both returns are above the ceiling with lengths of 12 and 8 feet two ninety bends one up one down. Hvac return air improvement guide.

It involves the heat output of the unit measured in british thermal units the air flow from its blower the number of vents and their location and the length of ducts needed to reach those vents. I have a three ton downflow furnace a c. Never locate ducts at the end of the trunk line run. 4 tons x 144 square inches return air duct in square inches.

Tees split but do not reduce and an appropriate reducer must be added. Calculate the return duct size based on the air conditioner s size and the type of duct you are using. Air intakes and outlets ventilation systems air intakes and outlets rules of thumbs. Use the following formulas.

While a duct sizing calculator built for a specific type of ductwork is the best possible method for sizing ducts the attached chart can be used in most single story homes with a centrally located unit and reasonable length duct runs. This article describes problems with return air inlet size location and ductwork. Particle diameter opening size. Size of air conditioner example.

How many square inches do i need to get the right airflow for 3 tons. Most technicians are skeptical about these numbers especially on the return air side of the system. In order for your forced air furnace to work properly you have to have the right sizes of duct vents in each room expelling air. How to increase hvac system return air to increase heating or cool air output by improving the flow of return air to the air handler.

These ductwork tips will help balance your air conditioning and heating system. Ventilation systems for ventilation and air handling air change rates ducts and pressure drops charts and diagrams and more. Particle diameter strainers and filters mesh size vs. Hvac ductwork sizing is critical for proper heating and cooling in every room.

Design 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 120 10x4 160 8x6 230 8x8 310 8x10 400 8x12 150 12x4 215 10x6 310 10x8 430 10x10 550 10x12 180 14x4 270 12x6 400 12x8 550 12x10 680 12x12 210 16x4 320 14x6 490 14x8 670 14x10 800 14x12 240 18x4 375 16x6 580 16x8 800 16x10 950 16x12 270 20x4 430 18x6 670 18x8 930 18x10 1100.