VSD SAVINGS CALCULATOR FOR PUMPS
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 B851, F/86/RevCMS 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:
Polynomial Coefficients A1, A2, A3 and A4:
Type of Flow Contorl  A1  A2  A3  A4 
1  55.21240  0.63700  0.00190  0.00000 
2  16.39683  0.05647  0.01237  0.00003 
3  13.51137  0.34467  0.01269  0.00007 
4  102.00000  0.00000  0.00000  0.00000 
VSD  27.44751  1.00853  0.01762  0.00000 
Equations:
Power at Design CFM = Nameplate Horsepower × Conversion Constant (kW/hp) × Motor Load at Design GPM / Nameplate Efficiency
Computed for each capacity level:
Percent of Design kW = A1 + (A2 × Capacity) + (A3 × (Capacity^{2})) + (A4 × (Capacity^{3}))
Percent of Design kW for VSD = A1 + (A2 × Capacity) + (A3 × (Capacity^{2})) + (A4 × (Capacity^{3}))
Percent of Design kW = A1 + (A2 × Capacity) + (A3 × (Capacity^{2})) + (A4 × (Capacity^{3}))
Percent of Design kW for VSD = A1 + (A2 × Capacity) + (A3 × (Capacity^{2})) + (A4 × (Capacity^{3}))
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)
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
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 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 Pumps
Nameplate Horsepower  hp  Annual Operating Hours  hp  
Nameplate Efficiency  %  Type of Flow Control  
Motor Load at Pump Design GPM  %  Cost of Electricity  RM/kWh  
Duty Cycle  


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 