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11. Checking motor and cable
1. Supply voltage
2. Current consumption
Items 3 and 4: Measurement is not necessary when the supply voltage and the current consumption are normal.
3. Winding resistance
4. Insulation resistance
12. Disposal
This product or parts of it must be disposed of in an
environmentally sound way:
1. Use the public or private waste collection service.
2. If this is not possible, contact the nearest Grundfos company
or service workshop.
Measure the voltage between the phases
by means of a voltmeter.
On single-phase motors, measure
between phase and neutral or between
two phases, depending on the type of
supply. Connect the voltmeter to the
terminals in the motor-protective circuit
breaker.
Measure the amps of each phase while
the pump is operating at a constant
discharge head (if possible, at the
performance where the motor is most
heavily loaded). For maximum operating
current, see nameplate.
Disconnect the submersible drop cable
from the motor-protective circuit breaker.
Measure the winding resistance between
the leads of the drop cable.
Disconnect the submersible drop cable
from the motor-protective circuit breaker.
Measure the insulation resistance from
each phase to earth (frame). Make sure
that the earth connection was made
carefully.
Subject to alterations.
The voltage should, when the motor is loaded, be within the
range specified in section
6. Electrical
The motor may burn if there are larger variations in voltage.
Large variations in voltage indicate poor power supply, and
the pump should be stopped until the defect has been
remedied.
On three-phase motors, the difference between the current in
the phase with the highest consumption and the current in the
phase with the lowest consumption should not exceed 5 %.
If so, or if the current exceeds the rated current, there are the
following possible faults:
• The contacts of the motor-protective circuit breaker are
burnt.
Replace the contacts or the control box for single-phase
operation.
• Poor connection in leads, possibly in the cable joint.
See item 3.
• Too high or too low supply voltage. See item 1.
• The motor windings are short-circuited or partly disjointed.
See item 3.
• Damaged pump is causing the motor to be overloaded.
Pull out the pump for overhaul.
• The resistance value of the motor windings deviates too
much (three-phase). Move the phases in phase order to a
more uniform load. If this does not help, see item 3.
For three-phase motors, the deviation between the highest
and the lowest value should not exceed 10 %. If the deviation
is higher, pull out the pump. Measure motor, motor cable and
drop cable separately, and repair or replace defective parts.
Note: The operating winding of single-phase 3-wire motors
will assume the lowest resistance value.
If the insulation resistance is less than 0.5 MΩ, the pump
should be pulled out for motor or cable repair.
Local regulations may specify other values for the insulation
resistance.
connection.
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