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Duct CFM Formula:
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The Duct CFM (Cubic Feet per Minute) calculation formula is used to determine the volume of air flow through a duct system. It is essential for HVAC system design, ventilation planning, and ensuring proper air distribution in buildings.
The calculator uses the duct CFM formula:
Where:
Explanation: The formula calculates the volume of air moving through a duct by multiplying the cross-sectional area of the duct by the velocity of the air flowing through it.
Details: Accurate CFM calculation is crucial for proper HVAC system design, ensuring adequate ventilation, maintaining indoor air quality, and optimizing energy efficiency in building systems.
Tips: Enter the cross-sectional area in square feet and air velocity in feet per minute. Both values must be positive numbers for accurate calculation.
Q1: What is a typical CFM range for residential HVAC systems?
A: Residential systems typically range from 400-2000 CFM depending on the size of the home and system capacity.
Q2: How do I measure duct cross-sectional area?
A: For rectangular ducts: multiply width × height. For round ducts: use π × (radius)². Convert to square feet if measurements are in inches.
Q3: What are typical air velocities in duct systems?
A: Recommended velocities are 600-900 fpm for main ducts, 500-700 fpm for branch ducts, and 300-500 fpm for final runs to maintain quiet operation.
Q4: Why is CFM important in HVAC design?
A: Proper CFM ensures adequate air distribution, maintains comfort levels, prevents hot/cold spots, and ensures equipment operates efficiently.
Q5: Can this formula be used for both supply and return ducts?
A: Yes, the formula applies to both supply and return air ducts, though return air velocities are typically lower to reduce noise.