AHU Capacity Calculator
Calculate air handling unit capacity quickly and accurately. Improve airflow efficiency and ensure proper cooling performance.
AHU Capacity Sizing Tool
How to Use AHU Capacity Calculator
Follow these simple steps to use an AHU capacity calculator:
Step 1: Enter Room Dimensions
Input length, width, and height of the room (in meters or feet). The calculator uses this to determine total air volume.
Step 2: Input Air Changes per Hour (ACH)
Enter the required ACH value. Typical values include:
- 1Offices: 4–6 ACH
- 2Hospitals: 6–12 ACH
- 3Labs: 10–15 ACH
Step 3: Add Occupancy Load
Enter the number of people in the space. This helps estimate heat and ventilation load.
Step 4: Include Equipment Load
Add heat load from machines, lighting, and appliances.
Step 5: Click Calculate
The AHU capacity calculator shows:
- Required CFM (Cubic Feet per Minute)
- Cooling capacity (TR or kW)
Tip: Always verify results with HVAC design standards.
How to Calculate AHU Capacity
Use this formula to calculate AHU capacity manually:
Where:
- Room Volume = Length × Width × Height
- ACH = Air Changes per Hour
Step-by-Step Example
Step 1: Calculate Room Volume
Room size = 10 m × 8 m × 3 m
Volume = 10 × 8 × 3
= 240 m³
Step 2: Select ACH
Assume ACH = 6 (for office)
Step 3: Convert Volume to CFM
First convert m³ to ft³:
240 m³ × 35.3147 =
8475.5 ft³
Step 4: Apply Formula
CFM = (8475.5 × 6) / 60
CFM = 847.55 ≈ 848 CFM
Step 5: Convert to Tons of Refrigeration (TR)
1 TR ≈ 400 CFM
TR = 848 / 400 = 2.12 TR
Final Answer: AHU Capacity ≈ 850 CFM or 2.1 TR
AHU Capacity Conversion Chart
| CFM | TR (Tons) | kW (Approx) |
|---|---|---|
| 400 CFM | 1 TR | 3.5 kW |
| 800 CFM | 2 TR | 7.0 kW |
| 1200 CFM | 3 TR | 10.5 kW |
| 1600 CFM | 4 TR | 14.0 kW |
| 2000 CFM | 5 TR | 17.5 kW |
| 2400 CFM | 6 TR | 21.0 kW |
Note: Values are approximate and depend on system efficiency.
FAQs – AHU Capacity Calculator
Air handling unit capacity is calculated by determining the total heat load of the space and converting it into required airflow in cubic feet per minute. You must account for room dimensions, desired air changes per hour, and sensible heat ratios to properly size the equipment for optimal comfort.
Standard air handling units range widely in capacity, typically starting from four hundred CFM for small residential applications up to fifty thousand CFM or more for massive industrial facilities. The exact capacity required depends entirely on the specific cooling or heating load of the building.
To calculate CFM for an air handling unit, multiply the volume of the room by the required air changes per hour, then divide that product by sixty. This straightforward formula ensures the system can deliver the appropriate volume of conditioned air to maintain proper ventilation and temperature.
An air handling unit is a large centralized system that distributes conditioned air throughout an entire building via ductwork. In contrast, a fan coil unit is a smaller, decentralized localized terminal device designed to heat or cool a single specific room without utilizing extensive duct systems.
In standard air conditioning applications, one ton of cooling capacity requires approximately four hundred cubic feet per minute of airflow. This rule of thumb helps engineers and technicians quickly estimate the necessary duct sizing and blower capacity for residential and commercial HVAC systems.
