The ceramic shaft used on many of these pumps can break. Sometimes the break
cannot be seen, even after tearing down the pump. Sometimes the connection to
the impeller is loose. If the impeller can be turned while the rotor is held still, the
assembly must be replaced.
Bell and Gossett and Grundfos Pumps
Bell and Gossett series SLC and most Grundfos series U pumps have a removable
plug at the rear of the motor. With the power off, unscrew the plug, and use a
screwdriver to manually turn and free the motor shaft.
Grundfos Pump Shaft
Courtesy of Grundfos Pumps Corp.
Once the impeller is freed, it will usually stay unstuck if the pump is run occasionally.
5.2 REPAIR PROCEDURES