Troubleshooting - Grundfos SPK Series Installation And Operating Instructions Manual

Troubleshooting

Preliminary Checks
Supply Voltage
How to Measure
Use a volt meter, (set to the proper
scale) measure 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
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 and indicate a poor electrical supply. 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.
Current Measurement
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.
Current should be measured when the
pump is operating at constant discharge
pressure.
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:
1. Burned contacts on motor starter.
2. Loose terminals in starter/terminal box or possible wire
defect.
3. Too high or too low supply voltage.
4. Motor windings are shorted or grounded. Check winding
and insulation resistances.
5. Pump is damaged causing a motor overload.
Lead-To-Ground Resistance
one ohmmeter lead to a motor lead and one to ground. Repeat
for each lead. If measured resistance does not exceed
1,000,000 ohms, motor is bad and in need of replacement.
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How to Measure
Turn off power and disconnect
the supply power leads in the
pump terminal box. Using an
ohmmeter, set the scale selector
to R x 100 and zero adjust the
meter by touching the two
ohmmeter leads together. Touch
Winding Resistance
Touch the leads of the ohmmeter to two motor leads.
Single phase motors - touching the leads of the ohmmeter
to the two outgoing "hot" motor leads (either a single motor
lead or combination of leads joined together) will measure
the main winding's resistance.
Three phase motors - touching the leads of the ohmmeter
to any two hot leads will measure that winding's resistance.
Repeat for all three possible lead combinations (L
L and L , L and L )
2 3 1 3
How to Measure — IEC
Turn off power and disconnect the supply power leads in the
pump terminal box. Using an ohmmeter, set the scale selector
to R x 1 and zero adjust the meter by touching the two
ohmmeter leads together.
Touch the leads of the ohmmeter to two motor terminals as
follows:
Delta Hookup
Terminals: U and X
V and Y
W and Z
Z X Y
W2 U2 V2
U V W
U1 V1 W1
INCOMING POWER SUPPLY
What it Means
If all ohm values are normal, the motor windings are neither
shorted nor open. If any one ohm value is less than normal
(-25%), that motor winding may be starting to short. If any one
ohm value is greater than normal (+25%), the winding may be
starting to open. If some values are high and some are low, the
leads may be connected incorrectly, or they may have a break in
the insulating jacket.
How to Measure — NEMA
Turn off power and disconnect
the supply power leads in the
pump terminal box. Using an
ohmmeter, set the scale selector
to R x 1 and zero adjust the
meter by touching the two
ohmmeter leads together.
and L
1
Y Hookup
Y
Terminals: U and X
V and Y
W and Z
Z X Y
W2 U2 V2
U V W
U1 V1 W1
INCOMING POWER SUPPLY
,
2