1. What is Exhaust Size Calculation?

The exhaust size calculation determines the appropriate diameter for ventilation systems based on airflow (CFM) and desired air velocity. Proper sizing ensures efficient system operation and adequate ventilation.

2. How Does the Calculator Work?

The calculator uses the exhaust size formula:

Where:

• \( cfm \) — Airflow in cubic feet per minute
• \( velocity \) — Air velocity in feet per second
• \( \pi \) — Mathematical constant Pi (~3.1416)

Explanation: The equation calculates the diameter needed to achieve the desired airflow at a specific velocity, accounting for the circular cross-sectional area of the duct.

3. Importance of Proper Exhaust Sizing

Details: Correct exhaust sizing is crucial for maintaining proper ventilation, minimizing energy consumption, reducing noise, and preventing system strain.

4. Using the Calculator

Tips: Enter CFM (airflow) in cubic feet per minute and desired velocity in feet per second. Typical velocities range from 800-1200 ft/min (13.3-20 ft/s) for main ducts and 600-900 ft/min (10-15 ft/s) for branch ducts.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical CFM for residential exhaust?
A: Bathroom fans typically range from 50-110 CFM, while kitchen range hoods may require 100-400 CFM depending on stove size.

Q2: What velocity should I aim for?
A: For general ventilation, 1000-1200 ft/min (16.7-20 ft/s) is common. Higher velocities increase noise and pressure drop.

Q3: How does diameter affect performance?
A: Smaller diameters increase velocity and noise while requiring more fan power. Larger diameters reduce velocity and noise but take up more space.

Q4: Should I round up or down?
A: Generally round up to the nearest standard duct size to ensure adequate airflow capacity.

Q5: Does this work for rectangular ducts?
A: The calculation provides equivalent circular diameter. For rectangular ducts, use equivalent diameter or calculate based on cross-sectional area.