Figure 68: Removing The Plastic Cable Cover On A Dc Power Supply In An Ex8200 - Juniper EX8208 Complete Hardware Manual

Complete Hardware Guide for EX8208 Ethernet Switches
174
Figure 68: Removing the Plastic Cable Cover on a DC Power Supply in an
EX8200 Switch
Remove the washers and nuts from each DC power input terminal, using the
4.
3/8-in. (9.5 mm) nut driver or socket wrench to loosen the nuts. Leave the bolts
installed on the input terminals.
Ensure that the power source circuit breaker is open so that the voltage across the
5.
DC power source cable leads is 0 V and that the cable leads do not become active
while you are connecting DC power.
Verify that the DC power cables are correctly labeled before making connections to
6.
the power supply. In a typical power distribution scheme where the return is connected
to chassis ground at the battery plant, you can use a multimeter to verify the resistance
of the and DC cables to chassis ground:
–48V RTN
The cable with very high resistance (indicating an open circuit) to chassis ground
is negative (–) and will be installed on the
The cable with very low resistance (indicating a closed circuit) to chassis ground is
positive (+) and will be installed on the
CAUTION: You must ensure that power connections maintain the proper
polarity. The power source cables might be labeled
their polarity. There is no standard color coding for DC power cables. The
color coding used by the external DC power source at your site determines
the color coding for the leads on the power cables that attach to the DC
power input terminals on each power supply.
Install each power cable lug on the DC power input terminal, securing it first with a
7.
locking washer, then with the nut (see Figure 69 on page 175). Apply between 29 in.-lb
(3.3 Nm) and 31 in.-lb (3.5 Nm) of torque to each nut. (Use the 3/8-in. [9.5 mm] nut
driver or socket wrench.)
a. Secure each positive (+) DC source power cable lug to the
input terminal.
(input) DC power input terminal.
–48V
(return) DC power input terminal.
RTN
and
(+)
RTN (return) DC power
Copyright © 2010, Juniper Networks, Inc.
to indicate
(–)