One of the most important problems for pumps during operation is the efficient detection of, and protection against dry running.

The most commonly used detection system is the use of float switches and level probes, although the reliability of these methods is rather limited given the operation faults that occur as a result of sludge and particle deposits on the electrodes, low water conductivity, etc.

Keeping the motor running in excessive overload conditions is equally important. This is normally carried out using thermal bi-metallic relays, although these are not always effective.

Other faults that usually occur are those related to the phase loss or phase sequence reversal in the case of three-phase pumps or voltage increases in single-phase pumps.

Just one of these occurrences could cause elevated losses, leaving the pumps out of service.

Fanox electronic relays are specifically designed for the complete protection of both single-phase and three-phase pumps, or of any other system where no load operation is critical.

The great adventage of these relays is that by using the motor itself as a  sensor, without the need for external detectors, they control the motor load and stop the motor before a costly fault occurs due to dry running, cavitation, closed valve, etc.

In this way awkward float switches and level probes are not required, therefore saving both time and money on installation and maintenance.

The underload is controlled by the measurement of undercurrent or of cos j for three-phase pumps or of just undercurrent for single-phase pumps.

The relays memorise the thermal image of the motor during its heating and cooling cycles thereby offering effective protection against overloads.

Other aspects worth pointing out are the protection against phase imbalance and phase failure and the detection of the phase sequence to ensure that the motor rotates in the right direction.

Fanox relays also provide protection against overvoltage in single-phase pumps.

The three-phase relays can also be fitted with the OD display moduel previously described.