Gorman-Rupp Pumps SF4C 1528832 and up - Manual (Page 23)

SF SERIES OM-06511
PAGE D - 3 TROUBLESHOOTING
ELECTRICAL TESTING
Make the electrical checks which follow to deter­
mine if pump malfunctions are being caused by
problems in the motor or in the motor cable.
Test Equipment
A volt/amp/ohmmeter and megohmmeter of ade­
quate range and quality are required to conduct
the electrical tests which follow.
Equipment Use
Ammeter To check AC Voltage
and current (amperage)
Ohmeter To measure resistance
(ohms) to ground
Refer to the wiring diagram(s) accompany­
ing the motor and control box before re­
connecting any electrical leads which have
been disconnected. Connections to the
wrong terminals may damage the motor
and/or control devices.
Voltage Imbalance
Use a voltmeter to read each phase of the incom­
ing 3 phase power. Each phase must balance with
the other two as closely as can be measured with a
commercial instrument. If the phases are out of
balance, contact your power company. If the
phases are balanced, check out the motor as de­
scribed in the following steps:
a. Use a voltmeter, Amprobe, or equivalent in­
strument to read the voltage of incoming
power lines 1 and 2, 2 and 3, and 1 and 3 at the
control box. Voltage must match as closely as
can be measured. If possible, measure the
voltage at the control box with:
1. The pump shut off.
2. The pump running in air.
3. The pump submerged and running under
full load.
The voltage measured under each condition
must be the same.
b. If voltage is balanced when the pump is off but
is imbalanced when the pump is running,
thoroughly check the power source, all inter­
connecting cables, and the pump motor to
isolate the defect.
c. Use an Amprobe or equivalent instrument to
measure the current draw (amperage) of
each phase while the pump is running under
full load, and with no load. In each condition,
the amperage readings for all three phases
must match as closely as can be measured.
Normal amperage values are listed in Table
B-1 in INSTALLATION; these values apply
only when the voltage at the site is the normal
voltage listed.
Power Cable Continuity
Set the megohmmeter at R x 1 scale and zero‐ba­
lance it. Test as follows:
a. Shut off incoming power to the control box,
and disconnect the motor power cable leads.
Connect the megohmmeter test leads to any
two cable leads, and note the megohmmeter
reading. A high resistance reading indicates
an open or broken circuit in the power cable or
motor windings, or a bad connection between
the motor and cable.
b. Repeat Step a. with each set of leads. The
three readings should be as close as can be
measured.
c. If readings indicate that continuity problems
exist in the motor or power cable, the motor
and/or terminal housing assembly must be re­
paired before putting the pump into service.
Insulation Resistance
Set the megohmmeter at R x 100, and zero‐ba­
lance it. Test as follows:
a. Shut off incoming power to the control box,
and disconnect the motor power cable leads.
Connect one megohmmeter test lead to the