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 will 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 201
and “DC Power Electrical Safety Guidelines” on page 197.
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.
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 79 on page 270 and Figure
78 on page 270).
NOTE: The DC power supply has four terminals labeled V+, V+, V–, and
V– for connecting DC power source cables labeled positive (+) and
negative (–). To provide power feed redundancy, the first set of terminals
should be powered by a dedicated power feed derived from feed A, and
the second set of terminals should be powered by a dedicated power feed
derived from feed B. This configuration provides the commonly deployed
A/B feed redundancy for the system.
a. Secure the ring lug of the positive (+) DC power source cable to the V+ terminal
on the DC power supply.
b. Secure the ring lug of the negative (–) DC power source cable to the V– terminal
on the DC power supply.
269Copyright © 2012, Juniper Networks, Inc.
Chapter 21: Installing a QFX3500 Node Device
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