1. What is Duct Size Calculation?

Duct size calculation determines the appropriate diameter of HVAC ducts based on air flow requirements. Proper duct sizing ensures efficient air distribution, minimizes energy loss, and maintains optimal system performance.

2. How Does the Calculator Work?

The calculator uses the duct size formula:

Where:

• \( CFM \) — Cubic feet per minute (air flow rate)
• \( FPM \) — Feet per minute (air velocity)
• \( \pi \) — Mathematical constant pi (approximately 3.1416)

Explanation: The formula calculates the duct diameter in inches based on the relationship between air flow rate (CFM) and air velocity (FPM).

3. Importance of Proper Duct Sizing

Details: Correct duct sizing is essential for maintaining proper air flow, reducing system noise, improving energy efficiency, and ensuring even temperature distribution throughout the space.

4. Using the Calculator

Tips: Enter CFM (cubic feet per minute) and FPM (feet per minute) values. Both values must be positive numbers greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

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

Q2: How does duct material affect sizing?
A: Different materials have different friction factors. This calculator provides theoretical size - actual installation may require adjustments based on duct material and layout.

Q3: What happens if ducts are undersized?
A: Undersized ducts can cause reduced airflow, increased noise, higher energy consumption, and uneven heating/cooling.

Q4: Are there standard duct sizes?
A: Yes, ducts typically come in standard sizes (4", 6", 8", 10", 12", etc.). The calculated size should be rounded to the nearest available standard size.

Q5: Should other factors be considered?
A: Yes, duct layout, number of bends, insulation, and static pressure should also be considered for complete HVAC system design.