To reduce the losses of the traditional circulator pump, Grundfos has developed a special alloy of ferritic steel for the rotor can.
Unlike asynchronous dry-runner standard motors the torque characteristic of a wet-runner circulator motor is weak. The slip depends on the hydraulic load and is not constant, but increases with the flow. Using “ferritic” stainless steel can be used to increase the performance of a pump or to decrease the power consumption by similar performance.
Between the stator and the rotor is the stainless steel rotor can, stretched as one part. There are 2 radial bearings and one axial. The shaft, the radial bearing, and one part of the axial bearing are made out of tungsten ceramics. This material is normally the hardest material inside a heating system. Especially the principle of hydrodynamics bearings means, that, if there is water inside the pump, the shaft is swimming upon a thin water film (like a tire at “aqua planning”).
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