22
15. Diagnosing specific problems
Problem Possible cause Remedy
The pump does not run. 1. No power at motor.
Check voltage at motor terminal box. If no voltage at motor, check
feeder panel for tripped circuits and reset circuit.
2.
Fuses are blown or circuit
breakers are tripped.
Turn off power and remove fuses. Check for continuity with
ohmmeter. Replace blown fuses or reset circuit breaker. If new
fuses blow or circuit breaker trips, the electrical installation, motor
and wires must be checked.
3.
Motor starter overloads are burned
or have tripped out.
Check for voltage on line and load side of starter. Replace burned
heaters or reset. Inspect starter for other damage. If heater trips
again, check the supply voltage and starter holding coil.
4. Starter does not energize.
Energize control circuit and check for voltage at the holding coil. If
no voltage, check control circuit fuses. If voltage, check holding
coil for shorts. Replace bad coil.
5. Defective controls.
Check all safety and pressure switches for operation. Inspect
contacts in control devices. Replace worn or defective parts or
controls.
6. Motor is defective.
Turn off power and disconnect wiring. Measure the lead to lead
resistances with ohmmeter (RX-1). Measure lead to ground values
with ohmmeter (RX-100K). Record measured values. If an open or
grounded winding is found, remove motor and repair or replace.
7.
Defective capacitor
(single-phase motors).
Turn off power and discharge capacitor. Check with ohmme-
ter (RX-100K). When the meter is connected to the capaci-
tor, the needle should jump towards 0 ohms and slowly drift
back to infinity (h). Replace if defective.
8. Pump is bound.
Turn off power and manually rotate pump shaft. If shaft does not
rotate easily, check coupling setting and adjust as necessary. If
shaft rotation is still tight, remove pump and inspect. Disassemble
and repair.
The pump runs but at reduced
capacity or does not deliver water.
1. Wrong rotation. Check wiring for proper connections. Correct wiring.
2. Pump is not primed or is airbound.
Turn pump off, close isolation valve(s), remove priming plug.
Check fluid level. Refill the pump, replace plug and start the pump.
Long suction lines must be filled before starting the pump.
3.
Strainers, check or foot valves are
clogged.
Remove strainer, screen or valve and inspect. Clean and replace.
Reprime pump.
4. Suction lift too large.
Install compound pressure gauge at the suction side of the pump.
Start pump and compare reading to performance data. Reduce
suction lift by lowering pump, increase suction line size or
removing high friction loss devices.
5.
Suction and/or discharge piping
leaks.
Pump spins backwards when turned off. Air in suction pipe.
Suction pipe, valves and fittings must be airtight. Repair any leaks
and retighten all loose fittings.
6. Pump worn.
Install pressure gauge, start pump, gradually close the discharge
valve and read pressure at shutoff. Convert measured pressure (in
psi) to head (in feet): (Measured psi x 2.31 ft/psi = ___ ft). Refer to
the specific pump curve for shutoff head for that pump model. If
head is close to curve, pump is probably OK. If not, remove pump
and inspect.
7.
Pump impeller or guide vane is
clogged.
Disassemble and inspect pump passageways. Remove any
foreign materials found.
8. Incorrect drain plug is installed.
If the proper drain plug is replaced with a standard plug, water will
recirculate internally. Replace with proper plug.
9. Improper coupling setting. Check/reset the coupling; see page 18.
Grundfos.bk Page 22 Wednesday, March 18, 2009 10:38 AM
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