This guide is intended to help identify the cause of pump failures and possible solutions to prevent reoccurrence.

System water quality e.g. sludge:
The pump is lubricated and cooled by the water flowing through it, sludge in the water will get into the bearings and motor restricting the flow through the internal parts of the pump which will cause
the bearings to run dry and the pump
to become hot and the motor to
eventually seize.

Restrictions in circulation:
If the flow circulation is restricted it can cause excessive pump load.
e.g. TRVs fitted, S-plan etc.
Ensure a properly adjusted by-pass is fitted.

Open vented systems - check that the cold feed and open vent are configured and positioned correctly (150mm apart max.) and that the header tank is filled to the correct level.

Sealed systems - ensure that the COLD system pressure is approximately 1.5bar.

The preferred arrangement is where the pump is installed in a vertical pipe pumping upwards with the pump shaft horizontal.

A pump installed in horizontal pipe work should be fitted on its side so that the pump shaft is horizontal or slightly higher at the vent plug end. This reduces the load on the bearings and ensures air can be purged from both the rotor chamber and impeller housing.

The pump should not be positioned with the body vertical as this can lead to the top bearing running dry which would cause noise and premature pump failure.