st4/st6 series submersible pumps• operation anD parts manual — rev. #1 (11/12/13) — page 25
TroubleshooTing
table 9. pump troubleshooting
sYmptom
possible problem
solution
Pump Fails To Start
Incorrect voltage/amps?
Check that the proper voltage, 230 or 460 VAC, 60
Hz, 3-phase is being supplied to the pump. Also
check that there is an adequate amount of current
(amps) to run the pump. Check power source circuit
breaker.
Check electrical connec-
tions?
If using float switches check wiring, inspect power
cord.
Blown power fuse or tripped
circuit breaker?
Replace fuse check circuit breaker, check cause of
blown fuse or tripped breaker.
Impeller locked?
Disconnect power cord and check for clogging. Un-
clog pump. Check overload protection device.
Wet motor windings?
Use multimeter to check motor insulation. Insulation
resistance must be approximately 15 megaohms. If
resistance is low, disassemble pump motor and bake
windings to dry them.
Defective motor and pump
bearings?
Check for excessive bearing wear, if worn replace
bearings. Replace motor if defective.
Pump Fails to Deliver Full
Output
Twisted or restricted dis-
charge hose?
Lay hose flat un-kinked. Remove clog from hose line.
Clogged pump strainer?
Clean strainer.
Low voltage?
Use a voltmeter to check voltage while pump is
energized. Voltage must be within ±10%. Check
power source (no load and load). If an extension cord
is used, make sure it has adequate current-carrying
capacity for the required length.See Table 5.
Impeller worn?
Replace impeller.
Water in Mechanical
Seal Oil
Defective mechanical seal?
Replace mechanical seal.
Loose Oil Fill Plug?
Tighten securely. Apply teflon tape.
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