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10. Troubleshooting
When working with electrical circuits, use caution to avoid electrical shocks. We recommend the use of rubber gloves and
boots.
Before starting any work on the pump, make sure that metal terminal boxes and motors are properly grounded. Failure to
ground the pump may result in serious electrical shock.
10.1 Preliminary tests
Supply voltage
Current measurement
Insulation resistance
8
How to measure
Use a voltmeter (set to proper scale) to mea-
sure the voltage at the pump terminal box or
starter.
On single-phase units, measure between
power leads L1 and L2 (or L1 and N for
115 volt units).
On three-phase units, measure between:
•
Power leads L1 and L2
•
Power leads L2 and L3
•
Power leads L3 and L1.
How to measure
Use an ammeter (set on the proper scale) to
measure the current on each power lead at
the terminal box or starter. See the motor
nameplate for amp draw information.
Current should be measured when the pump
is operating at constant discharge pressure.
How to measure
Turn off power and disconnect the supply
power leads in the pump terminal box. Using
an ohm- or mega ohmmeter, set the scale se-
lector to R x 100K and zero-adjust the meter.
Measure and record the resistance between
each of the terminals and ground.
What it means
When the motor is under load, the voltage
should be within ±10% of the rated voltage.
Larger voltage variation may cause winding
damage.
Large variations in the voltage indicate a
poor electrical supply, and the pump should
not be operated until these variations have
been corrected.
If the voltage constantly remains high or low,
the motor should be changed to the correct
supply voltage.
What it means
If the amp draw exceeds the listed service
factor amps (SFA) or if the current imbalance
is greater than 5% between each leg on
three-phase units, check the following:
•
Burned contacts on the motor starter.
•
Loose terminals in starter or terminal box
or possible wire defect.
•
Too high or too low supply voltage.
•
Motor windings are shorted or grounded.
Check winding and insulation resistances.
•
Pump is damaged causing a motor over-
load.
What it means
Motors of all hp, voltage, phase and cycle
duties have the same value of insulation re-
sistance. Resistance values for new motors
must exceed 1,000,000 ohms. If they do not,
the motor should be repaired or replaced.
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Table of Contents
Troubleshooting
