Juniper QFX5110, Hardware Manual

Page: 109 / 222

to chassis ground at the battery plant, you can use a multimeter to verify the resistance
of the –48V and RTN DC cables to chassis ground:
• The cable with very low resistance (indicating a closed circuit) to chassis ground is
positive (+) and will be installed on the V+ (return) DC power input terminal.
•
The cable with very high resistance (indicating an open circuit) to chassis ground
is negative (–) and will be installed on the V– (input) DC power input terminal.
CAUTION: You must ensure that power connections maintain the proper
polarity. The power source cables might be labeled (+) and (–) to indicate
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.
3.
Ensure that the input circuit breaker is open so that the voltage across the DC power
source cable leads is 0 V and that the cable leads do not become active while you
are connecting DC power.
NOTE: The V+ terminals are referred to as +RTN, and V– terminals are
referred to as –48 V in “DC Power Wiring Sequence Warning” on page 191
and “DC Power Electrical Safety Guidelines for Switches” on page 186 .
4.
Ensure that the power supplies are fully inserted in the chassis.
5.
Remove the terminal block cover. The terminal block cover is a piece of clear plastic
that snaps into place over the terminal block (see
Figure 29 on page 90 ).
6.
Remove the screws on the terminals using the screwdriver. Save the screws.
WARNING: Ensure that the power cables do not block access to device
components or drape where people can trip on them.
7.
Connect each power supply to the power sources. Secure power source cables to the
power supplies by screwing the ring lugs attached to the cables to the appropriate
terminals by using the screw from the terminals (see
Figure 29 on page 90 and
Figure 30 on page 91 ).
The QFX5110 is designed to operate with a DC power supply that has a single,
non-redundant, feed input. For source redundancy, two DC power supplies must be
installed in the QFX5110; connect source (A) to one power supply and connect source
89 Copyright © 2017, Juniper Networks, Inc.
Chapter 10: Connecting the Switch to Power