Connecting Dc Power To A Qfx5200-32C-Dc - Juniper QFX5200 Hardware Manual

• Multimeter (not provided)

Connecting DC Power to a QFX5200-32C-DC

To connect DC power to a QFX5200-32C:
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 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 201
Guidelines" on page
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
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.
197.
Figure 52 on page
and "DC Power Electrical Safety
119).
117