1. What is the Duct Size Calculation?

The duct size calculation determines the appropriate cross-sectional area of a duct based on airflow (CFM) and velocity. Proper duct sizing is essential for efficient HVAC system performance and energy conservation.

2. How Does the Calculator Work?

The calculator uses the duct size formula:

Where:

• \( A \) — Duct cross-sectional area (sq ft)
• \( CFM \) — Airflow rate (cubic feet per minute)
• \( V \) — Air velocity (feet per minute)

Explanation: This formula calculates the required duct area to maintain a specific airflow velocity, ensuring optimal system performance.

3. Importance of Proper Duct Sizing

Details: Correct duct sizing prevents energy loss, reduces noise, maintains proper airflow, and ensures even temperature distribution throughout the space.

4. Using the Calculator

Tips: Enter CFM in cubic feet per minute and velocity in feet per minute. Both values must be positive numbers for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical velocity range for HVAC ducts?
A: Residential systems typically use 600-900 ft/min, while commercial systems may use 1000-2000 ft/min depending on application.

Q2: How does duct shape affect the calculation?
A: The formula calculates area. For rectangular ducts, additional calculations are needed to determine width and height dimensions.

Q3: What factors influence CFM requirements?
A: Room size, occupancy, heat load, and system capacity all influence the required CFM for a space.

Q4: Why is velocity important in duct design?
A: Proper velocity ensures efficient air movement while minimizing noise, pressure drop, and energy consumption.

Q5: Can this calculator be used for both supply and return ducts?
A: Yes, the same formula applies to both supply and return duct sizing, though velocity recommendations may differ.