(a)  
P180 DC Power Distribution Panel
 1) 180E2, OVRD/JTSN PUMP CONT L CTR
 2) 180E3, JTSN PUMP CONT 2&3 OTBD
 3) 180E18, JTSN PUMP CONT 2&3 INBD
 4) 180H18, OVRD/JTSN PUMP CONT R CTR

 S 714-017
 (9)  Do the fault current detector operational test for the fault current detector that you replaced (AMM 28-31-14/501).
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 ALL  ú ú 02 Page 405 ú Jun 18/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 FAULT CURRENT DETECTOR - ADJUSTMENT/TEST
________________________________________
 1.  General_______
 A.  This procedure has one task that does a test of ground fault detectors used on override/jettison pump motors.
 B.  Ground fault detectors supply protection for the override/jettison pump motors if short circuits occur.
 C.  Each ground fault detector contains one current transformer and one printed-circuit board with a relay.
 D.  The three wires to each of the pump motors go through a hole in a current transformer.
 E.  The ground fault detectors operate as follows:
 (1)  
If there is no ground fault, the instantaneous sum of the currents in the motor wires is zero.

 (a)  
When the sum of the currents is zero, the detector is not operated.

 (2)  
If a ground fault occurs, the instantaneous sum of the currents in the motor wires will not be zero.

 (a)  
When the current is larger than 1.5 |0.5 amperes, the fault detector will close its internal relay.

 (b)  
Operation of the detector relay removes the control voltage from a relay that supplies 115 volts ac to the pump motor.

 (3)  
When a ground fault detector operates, its internal relay will latch closed until it is reset.

 (a)  
The detector is reset by the removal of its electrical power.

 F.  
The ground fault detectors are found in the main equipment center. The pumps are found adjacent to the applicable fuel tank.

 G.  
A ground fault detector test is done by the replacement of the applicable pump electrical connector with a special test box.

 H.  
Get access to the left side override/jettison pumps through the wheel well in the left wing landing gear. The left side pumps are:

 (1)  
M224, Center Tank Left

 (2)  
M222, Main No. 2 Forward

 (3)  
M223, Main No. 2 Aft

 I.  
Get access to the right side override/jettison pumps through the wheel well in the right wing landing gear. The right side pumps are:

 (1)  
M225, Center Tank Right

 (2)  
M227, Main No. 3 Forward

 (3)  
M226, Main No. 3 Aft

 TASK 28-31-14-715-001
 2.  Fault Current Detector Operational Test_______________________________________
 A.  Special Tools and Equipment
 (1)  G28013-16, Test equipment - Override/Jettison Fuel Pump, Fault Current Detector (recommended).
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 28-31-14
 ALL  ú ú 03 Page 501 ú Feb 15/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

INBOARD MAIN TANK INBOARD MAIN TANK OVERRIDE/JETTISON OVERRIDE/JETTISON PUMP SWITCHES PUMP SWITCHES

Fuel Override/Jettison System Component Location
Figure 501 (Sheet 1)

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 ALL  ú
 ú  03  Page 502
 ú  Oct 10/90 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
　
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