24-60-01
 ALL  ú ú 01 Page 404 ú Oct 10/95
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 (4)  
IPC 24-50-02

 (5)  
WDM 24-31-21, 24-32-12, 24-33-11, 24-33-12, 24-33-31

 (6)  
SSM 24-32-01, 24-33-01, 24-33-02, 24-33-03

 B.
Access

 (1)  
Location Zone
 116 Area Between Nose Gear Well and Fuselage, RH
 271 Passenger Cabin, LH

 (2)  
Access Panel
 P180 DC Power Distribution Panel
 P183 E33 Equipment Center Panel

 C.
Install Remote Control Circuit Breaker

 S 424-011
 (1)  
Position applicable remote control circuit breaker in panel, aligning screw holes.

 S 434-012

 (2)  
Install two screws securing RCCB to panel. Tighten screws.

 S 434-013

 (3)  
Remove the two terminal nuts and washers from each of the two terminal studs of the RCCB.

 S 434-014
 CAUTION: ENSURE EACH POWER LEAD IS CONNECTED TO PROPER TERMINAL STUD ON
_______ CIRCUIT BREAKER. INCORRECT INSTALLATION WILL RESULT IN CIRCUIT MALFUNCTION AND/OR DAMAGE TO EQUIPMENT.
 MAKE SURE ROUND WASHERS ARE INSTALLED BETWEEN TERMINAL NUT AND TERMINAL LEAD. DO NOT INSTALL ANY WASHERS BENEATH TERMINAL LEADS. THIS WILL RESULT IN LOCALIZED RESISTANCE HEATING WHICH COULD CAUSE BURNING OF CIRCUIT BREAKER TERMINALS.
 (4)  Connect the power leads to the terminal studs on the RCCB and secure with washers and nuts. Tighten nuts.
 S 434-015
 CAUTION: ENSURE EACH CONTROL WIRE IS INSTALLED IN THE CORRECT LOCATION
_______ ON CIRCUIT BREAKER. INCORRECT INSTALLATION WILL RESULT IN CIRCUIT MALFUNCTION AND/OR DAMAGE TO EQUIPMENT.
 (5)  Connect each of the control wires to the RCCB.
 NOTE: Reference WDM 20-83-00 for assembly instructions of
____
 the control wiring terminations.

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 24-60-01
 ALL  ú ú 01 Page 405 ú Oct 10/95
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 S 424-017
 (6)  
Secure access panel door.

 S 864-021

 (7)  
Connect the electrical connectors to the batteries:

 (a)  
Put the main battery connector (DM7423A) into the receptacle on the main battery.

 (b)  
Put the APU battery connector (DM7432A) into the receptacle on the APU battery.

 (c)  
Turn the knobs on the connectors clockwise with your hand until they are tight.

 D. Do a Test of the Remote Control Circuit Breaker
 S 864-018
 (1)  
Apply electrical power on the airplane (Ref 24-22-00/201).

 S 714-019

 (2)  
Perform DC electrical load distribution test for applicable RCCB (Ref 24-60-00/501).

 (3)  
Remove electrical power, if it is not necessary (Ref 24-22-00/201).

 S 864-022
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 24-60-01
 ALL  ú ú 01 Page 406 ú Oct 10/95
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 28-VOLT DC POWER DISTRIBUTION - DESCRIPTION AND OPERATION
_________________________________________________________
 1.  General_______
 A.  The dc power distribution system provides 28-volt dc power to all dc loads, both essential and nonessential loads, throughout the airplane. The four main 28-volt dc distribution buses, supplied by the four main transformer rectifier units (TRUs), power the majority of the dc loads.
 B.  The main and APU hot battery buses are powered by the battery/battery charger systems.
 C.  The main and APU battery buses can be powered from two possible power sources, dc bus 3 or their associated hot battery bus.
 D.  Two dc ground handling buses (powered by the external power TRUs) supply the dc loads required for airplane servicing and maintenance operations.
　
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