Air Conditioning Duct Size Calculator

Duct Area Formula:

\[ \text{Duct Area} = \frac{\text{CFM}}{\text{Velocity}} \]

Duct Area:

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1. What is the Air Conditioning Duct Size Calculator?

The Air Conditioning Duct Size Calculator determines the required duct area based on airflow (CFM) and air velocity. Proper duct sizing is essential for efficient HVAC system performance and optimal air distribution throughout the building.

2. How Does the Calculator Work?

The calculator uses the fundamental duct sizing formula:

\[ \text{Duct Area} = \frac{\text{CFM}}{\text{Velocity}} \]

Where:

\( \text{CFM} \) — Airflow in cubic feet per minute
\( \text{Velocity} \) — Air velocity in feet per minute (fpm)
\( \text{Duct Area} \) — Resulting duct cross-sectional area in square feet

Explanation: This formula calculates the required duct area to maintain proper air velocity for efficient system operation and comfort.

3. Importance of Proper Duct Sizing

Details: Correct duct sizing ensures optimal airflow, reduces energy consumption, minimizes noise, prevents pressure imbalances, and extends HVAC system lifespan. Undersized ducts can cause high static pressure and reduced airflow, while oversized ducts may lead to poor air distribution and increased costs.

4. Using the Calculator

Tips: Enter CFM (cubic feet per minute) and desired air velocity in fpm. For residential applications, typical velocities range from 400-900 fpm, while commercial systems may use 1000-2000 fpm. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the recommended velocity for residential ductwork?
A: For residential applications, 400-600 fpm is typically recommended for main ducts, and 300-500 fpm for branch ducts to maintain quiet operation.

Q2: How does duct shape affect sizing calculations?
A: Round ducts are more efficient than rectangular ducts. When converting between shapes, equivalent diameter calculations are used to maintain the same airflow capacity.

Q3: What factors influence CFM requirements?
A: CFM requirements depend on room size, heat load, number of occupants, equipment type, and building insulation levels. Professional load calculations are recommended.

Q4: Can velocity be too high or too low?
A: Yes, high velocity causes noise and pressure drops, while low velocity may not properly distribute air and can lead to temperature stratification.

Q5: Should duct sizing consider friction losses?
A: Yes, professional duct design includes friction loss calculations, duct length, number of elbows, and other factors that affect system performance.