1. What is the HVAC Ductwork Formula?

The ductwork formula calculates the required cross-sectional area of an HVAC duct based on the airflow rate (CFM) and desired air velocity. Proper duct sizing is essential for efficient HVAC system operation.

2. How Does the Calculator Work?

The calculator uses the duct area formula:

Where:

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

Explanation: The formula determines the necessary duct size to maintain proper air velocity for a given airflow rate.

3. Importance of Proper Duct Sizing

Details: Correct duct sizing ensures efficient airflow, proper system performance, noise reduction, and energy efficiency. Undersized ducts increase static pressure and reduce airflow, while oversized ducts can lead to poor air distribution.

4. Using the Calculator

Tips: Enter CFM (based on your HVAC system requirements) and desired air velocity (typically 600-900 fpm for supply ducts, 500-700 fpm for return ducts). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are typical air velocities for HVAC ducts?
A: Supply ducts: 600-900 fpm, Return ducts: 500-700 fpm, Low-velocity systems: 400-600 fpm, High-velocity systems: 1000-2000 fpm.

Q2: How do I convert duct area to dimensions?
A: For rectangular ducts, area = width × height. For round ducts, area = π × radius². Common aspect ratios are 1:1 (square) to 4:1 (rectangular).

Q3: What happens if ducts are too small?
A: Undersized ducts cause increased static pressure, reduced airflow, noise, and strain on the blower motor, decreasing efficiency and lifespan.

Q4: Does duct material affect sizing?
A: Material affects friction loss but not the basic area calculation. Different materials may require adjustments for equivalent length calculations.

Q5: Should I account for duct insulation?
A: Insulation thickness reduces internal dimensions. Always calculate based on internal dimensions for airflow purposes.