# VSD SAVINGS CALCULATOR FOR FANS

## References and Equations

### References: For the energy savings analysis, this tool used power curves developed from data obtained by measuring the operating characteristics of various fans and from information provided in "Flow Control", a Westinghouse publication, Bulliten B-851, F/86/Rev-CMS 8121. The curves are representative, not precise. Final economic analysis should be based on actual power (kW) measurements of the pumping system.

### Constants:

Conversion Constant (kW/hp) = 0.746
Polynomial Coefficients A1, A2, A3 and A4:
 Fan Type A1 A2 A3 A4 1 20.00000 0.06808 -0.00128 0.00009 2 47.26190 0.67944 -0.01554 0.00014 3 50.25833 0.71648 -0.01452 0.00013 4 20.41905 0.10983 0.00745 0.00000 5 55.92857 -0.56905 0.02462 -0.00014 6 16.39683 -0.05647 0.01237 -0.00003 VSD 5.90000 -0.19567 0.00766 0.00004

### Equations:

Power at Design CFM = Nameplate Horsepower × Conversion Constant (kW/hp) × Motor Load at Design CFM / Nameplate Efficiency
Computed for each capacity level:
Percent of Design kW = A1 + (A2 × Capacity) + (A3 × (Capacity2)) + (A4 × (Capacity3))
Percent of Design kW for VSD = A1 + (A2 × Capacity) + (A3 × (Capacity2)) + (A4 × (Capacity3))
Current Power (kW) = Percent of Design kW × (Power at Design CFM / 100)
VSD Power (kW) = Percent of Design kW for VSD × (Power at Design CFM / 100)
Current Energy (kWh) = Current Power (kW) × (Percent of time at this Capacity / 100) × Operating Hours
VSD Energy (kWh) = VSD Power (kW) × (Percent of time at this Capacity / 100) × Operating Hours
Current Annual Energy Use = sum of all Current Energy (kWh)
VSD Annual Energy Use = sum of all VSD Energy (kWh)
Annual Energy Savings = Current Annual Energy Use – VSD Annual Energy Use
Annual Cost Savings = Annual Energy Savings × Cost of Electricity
VSD Savings Calculator For Fans
Nameplate Horsepower hp Annual Operating Hours hp
Nameplate Efficiency % Fan Type
Motor Load at Fan Design CFM % Cost of Electricity RM/kWh
Duty Cycle
 Percent of (cfm) Percent of Time at this Capacity % % % % % % % % % % % % % % % % % % % %
Energy and Cost savings
Current Annual Energy use kWh/yr
VSD Annual Energy Use kWh/yr
Annual Energy Savings kWh/yr
Annual Cost Savings RM/yr