Liberty Pumps Engineered Pump Systems (EPS) - Manual (Page 6)

©Copyright 2014 Liberty Pumps Inc. All rights reserved 6
voltage should be measured at the implementation point, usually the control panel, with the pump running.
Measuring the voltage at the implementation point will show you what Voltage the pump is seeing. Measuring the
voltage while the pump is running will give you a good idea of the voltage drop while the pump is under load. A
pump should not be used in voltage extremes greater than it is designed to handle.
5) Check pump rotation (3 phase only)
Three phase power uses three separate alternating currents that peak at different integrals. With pumps that are
powered by three phase electric, the phase sequence of the motor must match the phase sequence of the power
source. When the sequences match, the pump will operate properly. However, when the phases are out of
order the pump will run backwards (i.e. the impeller will rotate in the wrong direction). This will cause an extreme
loss of performance and could raise the amps drawn, which could result in tripping an overload or circuit breaker.
To ensure that the power to the pump is installed correctly, always check the rotation of the pump before lowering
it into the pit. The correct rotation is shown below for a grinder and sewage pump (Figure B). If the pumps are
rotating in the wrong direction, turn off the power and reverse any two leads. This will reverse the phase
sequence and will correct the pump rotation.
6) Check to see if pump is jammed
The nature of sewage pumps is to pass solids. Each sewage pump has a solids-handling specification that it is
designed to pass. On the other hand a grinder pump will grind any solids into a slurry, and then pump them.
Occasionally, a pump being used to pump sewage will become jammed on a large solid, especially when it is not
the intended usage. When a pump is jammed, some foreign material is keeping the impeller or cutter (grinder
pumps only) from rotating, which effectively stops the motor. If a pump remains on in this condition, you should
be able to detect a humming noise coming from the pump and the pump will usually overheat itself and turn off
due to thermal overload. To check for a jam, the pump must be removed from the basin. Always disconnect the
pump from electrical power before checking for a jam. The pump inlet is located on the bottom of the pump, so
we recommend putting the pump on its side or fixturing it upside down to look at the inlet. Inspect the impeller or
cutter for any foreign material, and try to spin the motor shaft. If it is unable to rotate, the pump is jammed.
Locate the jam, and attempt to remove whatever is restricting the impeller or cutter. A grinder pump has such a
small gap, that it may require the cutter to be hit with a screwdriver and hammer in the reverse direction to
remove any foreign material.
Figure B – Pump Rotation