VSD SAVINGS CALCULATOR FOR PUMPS
References and Equations
References:
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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:
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 × (Capacity2)) + (A4 × (Capacity3))
Percent of Design kW for VSD = A1 + (A2 × Capacity) + (A3 × (Capacity2)) + (A4 × (Capacity3))
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)
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 | ||||||||||||||||||||||||||||||||||||||||||||
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| 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 |
