4. Remove the nut and washer from each power terminal stud. If no washers and nuts
are already installed, they should be in the accessory box.
5. Secure the cable lug on the DC power cable to the terminal stud, first with a washer,
then with a nut (see Figure 98 on page 222). Use a 7/16-in. (11 mm) nut driver or wrench
to tighten the nut. Apply between 23 lb-in. (2.6 Nm) and 25 lb-in. (2.8 Nm) of torque
to each nut:
a. Secure each positive (+) DC source power cable lug to a RTN (return) terminal.
b. Secure each negative (–) DC source power cable lug to a –48V (input) terminal.
NOTE: All inputs on the two-input 160-A DC power supply in slot PEM0
must be powered by dedicated power feeds derived from feed A, and all
inputs on the two-input 160-A DC power supply in slot PEM1 must be
poweredbydedicated powerfeedsderivedfromfeedB. Thisconfiguration
provides the commonly deployed A/B feed redundancy for the system.
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
terminal studs on each power supply.
6. Loosen the captive screws on the cable restraints on the right edge of the power
supply faceplate.
7. Route the positive and negative DC power cables through the top and bottom of each
cable restraint.
8. Tighten the cable restraint captive screws to hold the power cables in place.
9. Verify that the power cabling is correct, that the power cables are not touching or
blocking access to router components, and that they do not drape where people could
trip on them.
10. Replace the clear plastic cover over the terminal studs on the faceplate.
221Copyright © 2017, Juniper Networks, Inc.
Chapter 22: Providing Power to the T640
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