1. What is the Air Ductwork Equation?

The air ductwork equation calculates the cross-sectional area (A) of a duct needed to handle a specific airflow (CFM) at a given velocity (V). It's fundamental in HVAC system design to ensure proper airflow while minimizing noise and pressure drop.

2. How Does the Calculator Work?

The calculator uses the basic ductwork equation:

Where:

• \( A \) — Cross-sectional area of the duct (square feet)
• \( CFM \) — Airflow rate (cubic feet per minute)
• \( V \) — Air velocity (feet per minute)

Explanation: The equation balances airflow requirements with velocity constraints to determine proper duct sizing.

3. Importance of Ductwork Calculation

Details: Proper duct sizing is crucial for efficient HVAC operation, ensuring adequate airflow to all spaces while maintaining energy efficiency and minimizing noise.

4. Using the Calculator

Tips: Enter CFM (typically 350-400 CFM per ton of cooling) and desired velocity (typically 600-900 ft/min for supply ducts). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are typical velocity limits for ductwork?
A: Supply ducts: 600-900 ft/min, Return ducts: 500-700 ft/min, to balance noise and efficiency.

Q2: How does duct shape affect calculations?
A: Round ducts are most efficient, but rectangular ducts are common. Equivalent diameter calculations may be needed.

Q3: What CFM values are typical for residential systems?
A: Generally 350-400 CFM per ton of cooling capacity, but varies based on system design.

Q4: How does altitude affect these calculations?
A: At higher altitudes, air density decreases, requiring adjustments to CFM calculations.

Q5: What about pressure drop considerations?
A: This simple equation doesn't account for pressure drop, which requires more detailed calculations based on duct length, fittings, and material.