1. What is CFM?

CFM (Cubic Feet per Minute) is a measurement of airflow volume, indicating how much air flows through a given space in one minute. It is a crucial parameter in HVAC system design and analysis.

2. How Does the Calculator Work?

The calculator uses the CFM equation:

Where:

• \( CFM \) — Airflow in cubic feet per minute (ft³/min)
• \( \text{Duct Area} \) — Cross-sectional area of the duct in square feet (ft²)
• \( \text{Velocity} \) — Air velocity in feet per minute (fpm)

Explanation: This fundamental equation relates the volume of air moving through a duct to the duct's cross-sectional area and the speed of the airflow.

3. Importance of CFM Calculation

Details: Accurate CFM calculation is essential for proper HVAC system design, ensuring adequate ventilation, maintaining indoor air quality, and optimizing energy efficiency in heating and cooling systems.

4. Using the Calculator

Tips: Enter duct area in square feet and velocity in feet per minute. Both values must be positive numbers. For rectangular ducts, calculate area as width × height. For circular ducts, use π × (diameter/2)².

5. Frequently Asked Questions (FAQ)

Q1: What is a typical CFM range for residential HVAC systems?
A: Residential systems typically range from 400-2000 CFM depending on the home size and system capacity.

Q2: How do I calculate duct area for different duct shapes?
A: For rectangular ducts: width × height. For circular ducts: π × (diameter/2)². Remember to convert to square feet.

Q3: What velocity ranges are recommended for different duct types?
A: Supply ducts: 600-900 fpm, Return ducts: 500-700 fpm, depending on noise considerations and system design.

Q4: Why is CFM important in HVAC design?
A: Proper CFM ensures adequate air distribution, maintains comfort levels, prevents system strain, and optimizes energy efficiency.

Q5: Can this calculator be used for both supply and return air calculations?
A: Yes, the CFM formula applies to both supply and return airflow calculations in HVAC systems.