Emerson Process Management Bristol ControlWave ExpressPAC - Manual (Page 75)

ControlWave ExpressPAC Instruction Manual (CI-ControlWave EPAC)
Revised Mar-2011 Service & Troubleshooting 5-7
Use this procedure to remove or replace the CPU/System Controller
board and the Process I/O board.
1.
If the ControlWave ExpressPAC is running, place any critical
control processes under manual control.
2.
Open the enclosure cover.
3.
Shut down the ControlWave ExpressPAC by disconnecting the
power at the CPU/System Controller assembly terminal TB1
(and if applicable, TB2).
4.
Carefully remove the battery wires from CPU/System Controller
board connector TB1 (unplugged in step 3) making sure they
don’t contact each other.
5.
Loosen the four screws that secure the battery cover/radio
mounting plate to the one piece mounting bracket.
6.
Slide the battery cover/radio mounting plate toward the top of
the unit so that its slots clear the mounting screws and remove it.
If a radio or modem is present, carefully set the battery
cover/radio mounting plate to one side. Note: Lithium battery
systems are located on the inside of the battery cover/radio
mounting plate.
7.
Carefully remove the primary battery system (with cables
attached).
8.
To install the new battery system, reverse the steps you did in
steps 3 through 7, but perform the reversed steps in reverse
order. After you connect power, test the unit.
5.2.4 Removing/Replacing the Backup Battery
Note
: The CPU/System Controller board draws power from the backup
battery only if the board loses power. The system SRAM has a
standby current draw of 20 μA maximum for each part plus 2 μA
for the real time clock. For a ControlWave ExpressPAC
containing 2MB of SRAM, a worst-case current draw of 42 μA
allows a battery life of approximately 9,000 hours. This means
you should not need to replace a battery until the ControlWave
ExpressPAC has been in service for an extended period
(normally many years).
The CPU/System Controller board accommodates a 3 V, 300 mA
lithium coin cell backup battery housed in a coin-cell socket (S1).
A
supervisory circuit on the CPU switches to battery power when the
regulated 3.3 Vdc falls out of specification. The battery then provides
backup power for the real-time clock (RTC) and the system SRAM on
the CPU/System Controller board.