Energy Savings was halved due to 6" High Efficiency System


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In times of rising energy costs, new systems put more and more emphasis on the best possible efficiency. Here, Franklin Electric has set a new benchmark with its High Efficiency Systems (HES) up to 150 kW. Compared to standard asynchronous motors, energy savings of more than 20% have been achieved in numerous systems installed.

This application example at a Waterworks Association in Germany proved that with the new method of operation with a 6" system the energy consumption was even halved. The reduction due to motor technology comes from a constant good efficiency throughout the entire performance range as well as perfectly balanced electronic components.

Franklin Electric installed and put into operation a 6" 15 kW Franklin Electric High Efficiency System, consisting of a 304SS NEMA synchronous submersible motor (3000 l/min), an IP66 Variable Frequency Drive (VFD) and an IP54 du/dt output filter.

Initial situation: ­

  • 10 stage 60 m³/h borehole pump with asynchronous submersible motor installed at 31 m below ground
  • Well diameter of 400 mm and depth of 50 m with continuous OBO filter
  • Minimum cooling flow alongside the motor is granted with the help of an additional cooling sleeve
  • The installation is remotely operated
  • Due to intake requirements as well as geological characteristics (water quality, well yield etc.) the pump has to constantly deliver 40 m³/h into a manifold pipe. Depending on additional wells being connected, the delivery head varies between 57 to 91 m. As these required duty points are not directly on the Q/H curve, the volume has to be throttled mechanically.
  • In two years observed the pump ran an average of approximately 200 hours per month with an input of P1 = ~20 kW (see graph 1).

New installation:

  • 5 stage 60 m³/h borehole pump (existing) with a Franklin Electric HES installed at 31 m including the existing cooling sleeve.
  • Due to limited space the electronic parts (VFD in IP66 and du/dt filter in IP 54) were mounted outside the existing cabinet directly to the wall.
  • At a rotating speed of 48.2 Hz, the newly chosen pump accurately meets the duty point I of 40 m³/h at 91 m (see green solid curve).
  • The rotational speed will be adjusted by the preset process reference 40 m³/h (read by existing flow control unit) in case of changing operational conditions/pumping heads.  Duty point II at 39.7 Hz for 40 m³/h at 57 m (see blue solid curve).
  • Due to the reduced rotation speed, the efficiency curve “moves” left resulting in an improved hydraulic efficiency compared to nominal load (see blue dotted curve).
  • These two duty points can now be achieved with an input of P1 = 9.5 and 16.2 kW respectively (see graph 2).


Energy savings through highly efficient system:

Due to this new method of operation, the pump now works at an average input of P1 = ~10.3 kW.  Thus, the energy consumption is halved (~ 80 % reduction caused by the speed control and ~20 % due to new motor technology).

The savings from motor technology are primarily due to the consistently good efficiency across the entire performance range and the perfectly matched electronic components (see graph 3).

The start-up went quickly and smoothly because of the custom-designed VFD software specifically developed by Franklin Electric.

Graphs1plus2 EN