AHU CFM to TR Calculator Guide
Convert airflow (CFM) into cooling capacity (TR) quickly and accurately. This AHU CFM to TR calculator helps engineers, HVAC technicians, and beginners size systems with ease. Use this simple guide to understand calculations, formulas, and real-world applications.
CFM to TR Converter
How to Use AHU CFM to TR Calculator
Follow these simple steps to use the AHU CFM to TR calculator:
- 1Enter Airflow (CFM): Input the airflow value in cubic feet per minute (CFM). You can find this value from AHU specifications or duct design.
- 2Enter Temperature Difference (ΔT): Input the temperature difference between return air and supply air. Typical value ranges from 16°F to 22°F.
- 3Apply the Formula: The calculator uses a standard HVAC formula to convert CFM to TR.
- 4Get Instant Result: The tool displays the cooling capacity in Tons of Refrigeration (TR).
- 5Adjust Inputs if Needed: Modify CFM or ΔT to see how capacity changes.
Conversion / Calculation Guide
Formula to Convert AHU CFM to TR
Where:
- CFM = Airflow (Cubic Feet per Minute)
- ΔT = Temperature Difference (°F)
- 1.08 = Air constant
- 12000 = BTU/hr per Ton
Step-by-Step Example
Example:
CFM = 4000
ΔT = 20°F
Step 1: Multiply CFM and ΔT
4000 × 20 = 80,000
Step 2: Multiply by air constant
80,000 × 1.08 = 86,400
Step 3: Divide by 12,000
86,400 ÷ 12,000 = 7.2 TR
Final Answer: Cooling capacity = 7.2 TR
AHU CFM to TR Conversion Chart
Approximate values (ΔT = 20°F)
| CFM | TR |
|---|---|
| 400 | 0.72 |
| 800 | 1.44 |
| 1200 | 2.16 |
| 1600 | 2.88 |
| 2000 | 3.60 |
| 3000 | 5.40 |
| 4000 | 7.20 |
| 5000 | 9.00 |
| 6000 | 10.80 |
| 8000 | 14.40 |
| 10000 | 18.00 |
Note: Values may vary based on actual temperature difference and system conditions.
Unit Standardization: SI vs. Imperial Sizing in AHU CFM to TR
When working with AHU CFM to TR calculations, using consistent physical units is vital. Small translation errors between SI Metric units (like millimeters, kilowatts, and meters) and Imperial units (like AWG wire, horsepower, and feet) can lead to serious sizing errors:
| Dimension | SI Metric Unit | Imperial Unit | Conversion Conversion Factor |
|---|---|---|---|
| Power | Kilowatts (kW) | Horsepower (HP) | 1 kW ≈ 1.341 HP |
| Length | Meters (m) | Feet (ft) | 1 m ≈ 3.2808 ft |
| Flow Rate | Cubic meters/hr (m³/h) | Gallons/minute (GPM) | 1 m³/h ≈ 4.403 GPM |
Always perform unit checks before installing physical components for AHU CFM to TR to ensure they match equipment specification sheets.
FAQs – AHU CFM to TR Calculator
To convert airflow from cubic feet per minute to tons of refrigeration, you generally divide the total CFM by four hundred. This industry standard rule of thumb assumes standard air density and typical sensible heat ratios found in most conventional comfort cooling air conditioning applications.
In the HVAC industry, TR stands for Tons of Refrigeration, which is a unit of power used to describe the heat-extraction capacity of air conditioning equipment. One ton of refrigeration is equal to twelve thousand British Thermal Units per hour, representing the cooling power of melting ice.
A standard two-ton air conditioning unit typically operates at approximately eight hundred cubic feet per minute of airflow. Because the general industry guideline calls for four hundred CFM per ton of cooling capacity, a two-ton system relies on this flow rate to efficiently condition the space.
To calculate sensible cooling tonnage using airflow and temperature difference, multiply the CFM by the delta T, then multiply by the sensible heat constant of 1.08. Finally, divide this total sensible heat value by twelve thousand to convert the result into standard tons of refrigeration capacity.
The standard of four hundred CFM per ton is based on the typical psychrometric properties of air in comfort cooling applications. This specific ratio balances sensible and latent cooling capacities, ensuring the system can properly lower the temperature while effectively removing indoor humidity.