Grundfos Hydro Multi-E Series Installation And Operating Instructions Manual page 38

7. Leakage from a shaft seal. a) The shaft seal is defective.
8. There is noise when the
pumps are operating.
9. Very frequent starts and
stops.
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b) CRE and CRIE pumps:
The height adjustment of the pump shaft
is inaccurate.
a) The pumps are cavitating.
b) CRE and CRIE pumps:
The pumps do not rotate freely (frictional
resistance) due to inaccurate height
adjustment of the pump shaft.
a) The diaphragm tank precharge pressure
is wrong.
b) The difference between start and stop
pressures is too small.
Note: This situation will only arise if
emergency operation is installed.
Replace the shaft seal.
Re-adjust the shaft height.
Clean the inlet pipe or pumps and possibly the inlet
strainer.
Re-adjust the shaft height. See the CR, CRI, CRN
installation and operating instructions supplied with
Hydro Multi-E.
Check the precharge pressure.
Increase the differential pressure setting on each
pressure switch.