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Cisco Network Convergence System 4000 Series Hardware Installation Guide
Chapter 4 Installing Power Components
Connecting Power to the Chassis
Connecting Power to a DC-Powered Chassis
This section contains the procedures to connect the DC source power cables to a DC-powered chassis.
The color coding of source DC power cable leads depends on the color coding of the site DC power
source. Because there is no color code standard for source DC wiring, you must be sure that power
source cables are connected to the power module with the proper positive (+) and negative (–) polarity:
•
In some cases, the source DC cable leads might have a positive (+) or a negative (–) label. This is a
relatively safe indication of the polarity,
but you must verify the polarity by measuring the voltage
between the DC cable leads
. Be sure that the positive (+) and negative (–) cable leads match the
positive (+) and negative (–) labels on the power module when making the measurement.
•
Green (or green and yellow) cable typically indicates that it is a ground cable.
Caution
DC power modules contain circuitry to trip the breaker on the power module if the power module detects
a reverse polarity condition. No damage should occur from reverse polarity, but you should correct a
reverse-polarity condition immediately.
Warning
To ensure that power remains off while you are performing this procedure, lock-out/tag-out the DC
circuit breaker switch in the OFF (0) position until you are ready to turn it on.
Follow these steps to connect the DC source power cables to a DC power tray:
Step 1
Verify that the power switch is set to the OFF (0) position. The power switch is on the right of the power
tray.
Step 2
Remove the clear plastic safety covers that fit over the DC power connection terminal studs.
Step 3
Verify the following resistance values on both power shelves:
•
The resistance between the positive and negative power terminal studs of each input must be greater
than 90 KOhm.
•
The resistance between each positive terminal stud and bare metal surface on the power shelf must
be greater that 10 MOhms.
•
The resistance between each negative terminal stud and bare metal surface on the power shelf must
be greater that 10 MOhms.
Note
Typical hand held Ohm meters will not measure 10 MOhms; instead they will auto range to
acquire a measurement and give an out-of-range reading. This is an acceptable reading provided
that the meter is in calibration.
Step 4
Connect the DC power cables in the following order:
a.
Positive cable first.
b.
Negative cable last.
Step 5
for the other power modules installed in the tray.
Warning
To prevent injury and damage to the equipment, always attach the ground and source DC power cable
lugs to power tray terminals in the following order: (1) positive (+) to positive (+), (2) negative (–) to
negative (–).
