TM 10-4610-232-34
Table 2-1. Direct Support Troubleshooting Guide (Continued)
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
3. Distribution pump circuit breaker opens whenever distribution pump Is started, ROWPU shuts down when distribution
pump is started. (Ref. Schematic diagram FO-2, sheet 5, schematic lines 524-526).
Check for short circuits.
Shut down ROWPU and generator. Refer to electrical drawings in Appendix D and refer to distribution
pump will not start troubleshooting steps 10-13 (malfunction 1).
4. Distribution pump circuit breaker trips open repeatedly, distribution pump ground fault trips open repeatedly. (Ref.
Schematic diagram FO-1, sheet 5, schematic lines 524-530).
Step 1.
Step 2.
NOTE
This problem is hard to pin point directly as the two circuit breakers are electrically tied
together so that what affects one will usually trip the other even though each is sensing
different levels of short circuit. The direct-acting breaker will only trip when overcurrents
exceed its setpoint, such as a direct bolted short circuit. By contrast, an arcing short
circuit may amount to only a fraction of the direct-acting circuit breaker setpoint and not
cause it to trip. Arcing faults are typically caused by loose connections, the presence of
vermin, rodents, and insects in equipment, or insulation deterioration as a result of
mechanical damage, heat aging, or moisture, dust, and other contaminants. Since the
arcing type fault usually involves a flow of current in the ground path, the ground fault
circuit breaker monitors the ground circuit for current flow. When it senses current in the
ground circuit it will trip and also trip out the pump circuit breaker. Under other circuit
conditions — balanced, unbalanced, or single-phase load currents, or single or three
phase short circuits not involving ground — it will not trip even though the pump breaker
does. For these reasons the following troublehshooting steps are very general and
success in isolating the problem relies on the electrician to carefully inspect all cables,
connectors, and connections for signs of damage or moisture intrusion. In some cases
only the substitution of known reliable components will identify the cause.
Shut down ROWPU and generator. Refer to electrical drawings in Appendix D and check all connections on
the ground fault interrupt (GFI 2) (REF: Interconnection diagram FO-2, Sheet 13), the current sensor (CS2)
(REF: Interconnection diagram FO-2, Sheet 10), and the CB3 (REF: Interconnection diagram FO-2, Sheet 10)
shunt wires for tightness.
(a) Tighten any loose wires.
(b) Refer to para. 2-24 and follow the procedures for testing the ground fault relay.
If none of the above checks reveal the problem, do the following in the order shown.
(a) Replace GFI 2 and CS2 (para. 2-24 and 2-25).
(b) Replace CB3 (para. 2-25).
5. Distribution pump circuit breaker will not reset, distribution pump ground fault will not reset. (Ref. Schematic diagram
FO-1. sheet 5. schematic lines 524-530).
Step 7.
Step 2.
Step 3.
Check distribution pump ground fault reset switch.
Reset the ground fault and then reset the distribution pump circuit breaker.
Shut down ROWPU and generator. Refer to electrical drawings in Appendix D and reset the distribution
pump circuit breaker.
Replace circuit breaker CB3 (REF: Interconnection diagram FO-2, Sheet 10) if it will not stay set (para.
2-25).
Remove wire #324 and #2A from GFI 2 (REF: Interconnection diagram FO-2, Sheet 13). Check continuity,
point-to-point, from transformer T1(X1) (REF: Interconnection diagram FO-2, Sheet 10) to wire #324A.
Repeat procedure for T1(X2) to wire #2A.
(a) Repair any loose or damaged wire (para. 2-20).
(b) Replace circuit breakers CB7 or CB10 (REF: Interconnection diagram FO-2, Sheet 8) if open (para.
2-23).
(c) Replace switch PB3 (REF: Interconnection diagram FO-2, Sheet 11), if open (para. 2-22).
(d) If all the above checks are okay, replace GFI 2 (para. 2-24)
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