Table 2-1. Direct Support Troubleshooting Guide (Continued)
TEST OR INSPECTION
7. Raw water pump circuit breaker trips repeatedly, raw water ground fault trips repeatedly. (Ref. schematic diagram
FO-1, sheet 5, schematic Iines 532-537).
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 circuit 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, 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 troubleshooting 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.
Step 1. Shutdown ROWPU and generator. Refer to electrical drawings in Appendix D. Check all connections on the
ground fault interrupt (GFI 1) (REF: Interconnection diagram FO-2, Sheet 13), the current sensor (CS1) (REF:
Interconnection diagram FO-2, Sheet 10), and the CB4 (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.
Step 2. If none of the above checks reveal the problem, do the following in the order shown.
(a) Replace GFI 1 and CS1 (para. 2-25).
(b) Replace CB4 (para. 2-24).
8. Raw water pump circuit breaker will not reset, raw water pump ground fault will not reset. (Ref. Schematic diagram
FO-1, sheet 5, schematic lines 532-537).
Step 1. Check raw water pump ground fault reset switch.
Reset the ground fault and then reset the raw water pump circuit breaker.
Step 2. Shut down ROWPU and generator. Refer to electrical drawings in Appendix D and replace circuit breaker
CB4 (REF: Interconnection diagram FO-2, Sheet 10) if it will not stay set.
Reset the raw water pump circuit breaker.
Step 3. Remove wires #204 and #2B from GFI 1 (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 #204. Repeat
the procedure from T1(X2) to wire #2B.
(a) Repair any loose or damaged wire (para. 2-20).
(b) Replace circuit breakers CB7 (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 1 (para. 2-24).
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