Installation of the AC Essential Bus Switching Contactor

TASK 24-25-55-400-001-A
Installation of the AC Essential Bus Switching Contactor

WARNING: MAKE SURE THAT NO AC OR DC POWER IS CONNECTED TO THE AIRCRAFT ELECTRICAL CIRCUITS. THERE IS A RISK OF ELECTROCUTION IF THE AC OR DC POWER STAYS CONNECTED.

ZONE: 125
FIN: 3XC

1. Reason for the Job
Self explanatory
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE
No specific	AR	WARNING NOTICE(S)
No specific	Torque wrench: range to between 0.176 and 0.147 m.daN (15.58 and 13.01 lbf.in )

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
125	LATERAL AVIONIC COMPARTMENT
812

C. Referenced Information

REFERENCE	DESIGNATION
TASK 24-25-00-710-001-A	Operational Check of AC ESS Generation Switching
Contactor

3. Job Set-up
Subtask 24-25-55-860-050-A

A. Aircraft Maintenance Configuration
(1) In the cockpit, on the overhead panel 35VU, make sure that these puhbutton switches are released:

BAT 1, BAT 2,
GEN 1, GEN 2,
EXT A.

(2) In the cockpit, make sure that the WARNING NOTICE(S) is in position to tell persons not to operate the pushbutton switches on these panels of the overhead panels:

35VU (ELEC),
21VU (EMER ELEC PWR).

(3) Make sure that the external power connector is not connected to the aircraft receptable EXT PWR A.
(4) On the access door 121AL, make sure that the WARNING NOTICE(S) is in position to tell persons not to connect the external power connector.
(5) Make sure that the ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE is in position at the access door 812.
(6) Make sure that the access door 812 is open.
(7) In the avionics compartment, make sure that the access door (14) is removed from the panel 106VU.

Subtask 24-25-55-865-050-A

B. Make sure that this(these) circuit breaker(s) is(are) open, safetied and tagged:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
105VU	ELEC/CSM/G /EV AUTO/SPLY	7XE	C01
106VU	CSM/G /EV/MAN/SPLY	6XE	B04
106VU	ESS TR/SPLY	4PE	C01
122VU	ELEC/CNTOR/ESS/DC BUS/TIE	3PC	W26
123VU	AC ESS/BUS ON/BUS 1	1XC	AC12
123VU	AC ESS/BUS ON/BUS 2	2XC	AC01

4. Procedure
Subtask 24-25-55-420-050-A

A. Installation of the Contactor
(1) Clean the component interfaces and the adjacent area.
(2) Do an inspection of the component interfaces and the adjacent area.
(3) Put the contactor (8) in position on the studs (11).
(4) Install the washers (9) and the nuts (7), then tighten the nuts.
(5) Install the electrical wires:

CAUTION: REFER TO THE MATCH MARKS MADE DURING THE REMOVAL WHEN YOU CONNECT THE ELECTRICAL WIRES. INCORRECT CONNECTION OF THE WIRES WILL CAUSE DAMAGE TO EQUIPMENT.

(a) Install the electrical power-supply wires (6).
(b) Install the plates (5) and (10), the spring washers (4) and the nuts (3),
(c) TORQUE the nuts (3) to between 0.176 and 0.147 m.daN (15.58 and 13.01 lbf.in )

.
(6) Remove the CAP-BLANKING from each electrical connector and receptacle.
(7) Make sure that all the electrical connections are clean and in the correct condition.
(8) Connect the 2 electrical connectors (1, 2).

Subtask 24-25-55-865-051-A

B. Remove the safety clip(s) and the tag(s) and close this(these) circuit breaker(s):

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
105VU	ELEC/CSM/G /EV AUTO/SPLY	7XE	C01
106VU	CSM/G /EV/MAN/SPLY	6XE	B04
106VU	ESS TR/SPLY	4PE	C01
122VU	ELEC/CNTOR/ESS/DC BUS/TIE	3PC	W26
123VU	AC ESS/BUS ON/BUS 1	1XC	AC12
123VU	AC ESS/BUS ON/BUS 2	2XC	AC01

Subtask 24-25-55-710-050-A

C. Do an operational test of the AC essential generation switching (Ref. AMM TASK 24-25-00-710-001).

5. Close-up
Subtask 24-25-55-410-050-A

A. Close Access
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Install the access door (14) on the panel 106VU.
(3) Remove the WARNING NOTICE(S).
(4) Close the access door 812.
(5) Remove the access platform(s).

[Rev.10 from 2021] 2026.03.31 23:22:51 UTC