Diagnosing Specific Problems - Grundfos CR Series Installation And Operation Manual

Diagnosing specific problems

Problem
The pump does not run
The pump runs but at
reduced capacity or
does not deliver water
Possible cause
1. No power at motor.
2. Fuses are blown or circuit
breakers are tripped.
3. Motor starter overloads are
burned or have tripped out.
4. Starter does not energize.
5. Defective controls.
6. Motor is defective.
7. Defective capacitor.
(Single-phase motors)
8. Pump is bound.
1. Wrong rotation
2. Pump is not primed or is
airbound.
3. Strainers, check or foot valves
are clogged.
4. Suction lift too large.
5. Suction and/or discharge
piping leaks.
6. Pump worn.
7. Pump impeller or guide vane
is clogged.
Remedy
Check for voltage at motor teminal box. If no voltage at motor,
check feeder panel for tripped circuits and reset circuit.
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.
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.
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.
Check all safety and pressure switches for operation. Inspect
contacts in control devices. Replace worn or defective parts or
controls.
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.
Turn off power and discharge capacitor. Check with ohmmeter
(RX-100K). When the meter is connected to the capacitor, the
needle should jump towards 0 ohms and slowly drift back to
infinity ( ). Replace if defective.
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.
Check wiring for proper connections. Correct wiring.
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.
Remove strainer, screen or valve and inspect. Clean and replace.
Reprime pump.
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.
Pump runs backwards when turned off. Air in suction pipe.
Suction pipe, valves and fittings must be airtight. Repair any
leaks and retighten all loose fittings.
Install pressure gauge, start pump, gradually close the
discharge valve and read pressure at shutoff.
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.
Disassemble and inspect pump passageways. Remove any
foreign materials found.
Convert
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