Juniper EX4550 - Page 188

connecting earth ground, see “Connecting Earth Ground to an EX Series
Switch” on page 157.
•
Install the power supply in the chassis. For instructions on installing a DC power supply
in an EX4550 switch, see “Installing a DC Power Supply in an EX4550 Switch” on
page 206.
Ensure that you have the following parts and tools available:
•
DC power source cables (14–16 AWG) with ring lug (Molex 190700069 or equivalent)
(not provided)
•
Phillips (+) screwdriver, number 2 (not provided)
•
Multimeter (not provided)
To connect DC power to an EX4550 switch:
1. Attach the grounding strap to your bare wrist and to a site ESD point.
2. Verify that the DC power cables are correctly labeled before making connections to
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 –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 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 296
and “DC Power Electrical Safety Guidelines” on page 292.
4. Ensure that the power supplies are fully inserted in the chassis.
Copyright © 2015, Juniper Networks, Inc.166
EX4550 Switch Hardware Guide