System Duty Point Calculator
Calculate the total system duty point (Flow & Pressure) and validate existing fans for your LEV system.
1. System Configuration
2. Extraction Point Details
System Overview & Documentation
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3. System Duty Point & Fan Recommendation
Total Fan Flowrate
0 m³/hRequired Fan Pressure
0 PaRecommended Main Duct
Actual Main Duct Velocity
0.0 m/s4. Check if an Existing Fan is Suitable ("Back-Filing")
Enter the specifications of your fan to see if it's suitable and how it would perform in this system.
5. Calculation Notes & Used Values
How the Fan Pressure is Calculated
The total pressure a fan must overcome (the "System Duty Point") is the sum of pressure losses along the single most difficult path in the system, known as the Index Run. It is calculated as:
Total Pressure = (Index Run Branch Loss) + (Main Duct Loss) + (Component Loss)
- Index Run Branch Loss: This is the friction loss from the single extraction point with the highest resistance. The fan must be powerful enough for this worst-case path.
- Main Duct Loss: This is the friction loss in the main duct. Its length is estimated as 12 meters per extraction point.
- Component Loss: This is the manual value you entered for all other sources of resistance, such as filters, silencers, cyclones, or sharp bends.
Friction Loss
Friction loss is the pressure lost as air moves against the inner walls of the duct. This calculator uses a simplified formula derived from the Darcy-Weisbach equation. This shows that doubling the velocity quadruples the pressure loss, making velocity a critical factor in fan sizing.