Preliminary Tests - Grundfos Redi-Flo4 Installation And Operating Instructions Manual

TROUBLESHOOTING

Preliminary Tests

SUPPLY
VOLTAGE
CURRENT
MEASUREMENT
WINDING
RESISTANCE
INSULATION
RESISTANCE
7
How to Measure
By means of a voltmeter, which has
been set to the proper scale, measure
the voltage at the control box. On single-
phase units, measure between line and
neutral.
How to Measure
By use of an ammeter, set on the proper
scale, measure the current on each
power lead at the control box. See the
Electrical Data, Table C, for motor amp
draw information.
Current should be measured when the
pump is operating at a constant
discharge pressure with the motor fully
loaded.
How to Measure
Turn off power and disconnect the drop
cable leads in the control box. Using an
ohmmeter, set the scale selectors to
Rx1 for values under 10 ohms and Rx10
for values over 10 ohms.
Zero-adjust the meter and measure the
resistance between leads. Record the
values.
Motor resistance values can be found
in Electrical Data, Table C. Cable
resistance values are in Table D.
How to Measure
Turn off power and disconnect the drop
cable leads in the control box. Using an
ohm or mega ohmmeter, set the scale
selector to Rx 100K and zero-adjust the
meter.
Measure the resistance between the
lead and ground (discharge pipe or well
casing, if steel).
What it Means
When the motor is under load, the
voltage should be within ± 10% of the
nameplate 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), check for
the following:
1. Loose terminals in control box or
possible cable defect. Check winding
and insulation resistances.
3. Too high or low supply voltage.
4. Motor windings are shorted.
5. Pump is damaged causing a motor
overload.
What it Means
If all the ohm values are normal, and the
cable colors correct, the windings are
not damaged. If any one ohm value is
less than normal, the motor may be
shorted. If any one ohm value is greater
than normal, there is a poor cable
connection or joint. The windings or
cable may also be open. If some of the
ohm values are greater than normal and
some less, the drop cable leads are
mixed. To verify lead colors, see
resistance values in Electrical Data,
Table C.
What it Means
For ohm values, refer to table below.
Motors of all Hp, voltage, phase and
cycle duties have the same value of
insulation resistance.