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Duct Sizing Formula:
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Duct sizing calculation determines the appropriate cross-sectional area for HVAC ductwork based on airflow requirements (CFM) and desired air velocity. Proper duct sizing ensures efficient airflow, reduces energy consumption, and maintains optimal system performance.
The calculator uses the duct sizing formula:
Where:
Explanation: The formula calculates the required duct area by dividing the airflow rate by the desired air velocity.
Details: Correct duct sizing is essential for maintaining proper air distribution, minimizing pressure drops, reducing noise, and ensuring energy efficiency in HVAC systems.
Tips: Enter CFM (cubic feet per minute) and desired air velocity (feet per minute). Both values must be positive numbers. The calculator will determine the required duct area in square feet.
Q1: What is the typical air velocity for HVAC ducts?
A: Residential systems typically use 600-900 FPM for supply ducts and 500-700 FPM for return ducts. Commercial systems may use higher velocities.
Q2: How does duct shape affect sizing calculations?
A: The formula calculates area. For rectangular ducts, this area must be converted to appropriate width and height dimensions based on aspect ratio preferences.
Q3: What factors influence CFM requirements?
A: Room size, occupancy, heat load, and the specific HVAC system capacity all influence the required CFM for each space.
Q4: Are there limitations to this calculation method?
A: This basic formula doesn't account for friction losses, duct material, or system static pressure, which are important in comprehensive duct design.
Q5: Should this calculation be used for all duct types?
A: While the basic principle applies to all ducts, different applications (supply, return, exhaust) may have different velocity recommendations.