1. What is Duct Size Calculation?

Duct size calculation determines the appropriate diameter for HVAC ductwork based on airflow (CFM) and velocity (FPM) requirements. Proper duct sizing ensures efficient air distribution and system performance.

2. How Does the Calculator Work?

The calculator uses the duct size formulas:

Where:

• \( A \) — Cross-sectional area (sq ft)
• \( CFM \) — Airflow in cubic feet per minute
• \( V \) — Velocity in feet per minute (FPM)
• \( D \) — Duct diameter (inches)

Explanation: The formula calculates the required duct area based on airflow and velocity, then converts it to diameter for round ducts.

3. Importance of Proper Duct Sizing

Details: Correct duct sizing is crucial for maintaining proper airflow, minimizing pressure drops, reducing noise, and ensuring energy efficiency in HVAC systems.

4. Using the Calculator

Tips: Enter CFM (cubic feet per minute) and velocity (feet per minute). Both values must be positive numbers. The calculator will provide the required duct diameter in inches.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical velocity range for HVAC ducts?
A: Residential systems typically use 600-900 FPM for supply ducts and 500-700 FPM for return ducts.

Q2: How does duct shape affect the calculation?
A: This calculator is for round ducts. For rectangular ducts, additional calculations are needed to determine equivalent round diameter.

Q3: What factors influence duct sizing?
A: Airflow requirements, system static pressure, duct material, layout complexity, and noise considerations all affect duct sizing.

Q4: When should I consult an HVAC professional?
A: For complex systems, commercial applications, or when dealing with unusual layout constraints, professional HVAC design is recommended.

Q5: Are there standard duct sizes?
A: Yes, ductwork typically comes in standard sizes (4", 6", 8", 10", 12", etc.), so the calculated size should be rounded to the nearest available standard size.