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Duct Area Formula:
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Duct sizing is the process of determining the appropriate cross-sectional area for air ducts in HVAC systems to ensure efficient airflow while maintaining proper velocity and pressure.
The calculator uses the fundamental duct sizing formula:
Where:
Explanation: This formula calculates the required duct area based on the desired airflow rate and velocity to ensure optimal system performance.
Details: Proper duct sizing is crucial for efficient HVAC operation. Undersized ducts cause high velocity, noise, and pressure drops, while oversized ducts lead to poor airflow distribution and energy waste.
Tips: Enter CFM (cubic feet per minute) and desired velocity (feet per minute). Typical residential velocities range from 600-900 fpm for supply ducts and 500-700 fpm for return ducts.
Q1: What is the recommended velocity for residential ducts?
A: For supply ducts: 600-900 fpm, for return ducts: 500-700 fpm. Lower velocities reduce noise but require larger ducts.
Q2: How does duct shape affect sizing?
A: Round ducts are more efficient than rectangular ones. When converting, maintain equivalent cross-sectional area using duct conversion charts.
Q3: What factors influence CFM requirements?
A: Room size, insulation, windows, occupancy, and equipment capacity all affect the required CFM for proper heating and cooling.
Q4: When should I use higher velocities?
A: Higher velocities (up to 1200 fpm) may be used in commercial applications or where space constraints require smaller ducts, but noise increases.
Q5: How accurate is this calculator for complex systems?
A: This provides basic sizing. Complex systems require professional manual D calculations considering friction loss, fittings, and system static pressure.