1. What is CFM and FPM?

CFM (Cubic Feet per Minute) and FPM (Feet per Minute) are measurements used in HVAC systems to quantify air flow. CFM represents the volume of air flow, while FPM represents the velocity of air flow.

2. How Does the Calculator Work?

The calculator uses the CFM formula:

Where:

• \( FPM \) — Feet per minute (air velocity)
• \( \text{Duct Area} \) — Cross-sectional area of the duct in square feet
• \( CFM \) — Cubic feet per minute (air flow volume)

Explanation: The equation calculates the volume of air moving through a duct based on the air velocity and the cross-sectional area of the duct.

3. Importance of CFM Calculation

Details: Accurate CFM calculation is crucial 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 FPM in feet per minute and duct area in square feet. Both values must be positive numbers. The calculator will compute the CFM (cubic feet per minute) of air flow.

5. Frequently Asked Questions (FAQ)

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

Q2: How do I calculate duct area for rectangular ducts?
A: For rectangular ducts, multiply the width by the height (both in feet) to get the cross-sectional area in square feet.

Q3: How do I calculate duct area for round ducts?
A: For round ducts, use the formula: Area = π × (diameter/2)², where diameter is in feet.

Q4: Why is CFM important in HVAC design?
A: CFM determines how much air is being moved through a system, which affects temperature control, humidity regulation, and air quality throughout the building.

Q5: What factors can affect CFM calculations?
A: Duct material, bends in the ductwork, filters, and other obstructions can create friction that reduces actual CFM compared to theoretical calculations.