Juniper Networks MX480 User Manual

Page 257

23 lb-in. (2.6 Nm) and 25 lb-in. (2.8 Nm) of torque to each nut. Do not overtighten the
nut. (Use a 7/16-in. [11 mm] torque-controlled driver or socket wrench.)

a. Secure the positive (+) DC source power cable lug to the

RTN

(return) terminal.

b. Secure the negative (–) DC source power cable lug to the

–48V

(input) terminal.

CAUTION:

Ensure that each power cable lug seats flush against the surface

of the terminal block as you are tightening the nuts. Ensure that each nut
is properly threaded onto the terminal stud. The nut should be able to spin
freely with your fingers when it is first placed onto the terminal stud.
Applying installation torque to the nut when improperly threaded may
result in damage to the terminal stud.

CAUTION:

The maximum torque rating of the terminal studs on the DC

power supply is 36 lb-in. (4.0 Nm). The terminal studs may be damaged
if excessive torque is applied. Use only a torque-controlled driver or socket
wrench to tighten nuts on the DC power supply terminal studs.

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.

NOTE:

The DC power supplies in

PEM0

and

PEM1

must be powered by

dedicated power feeds derived from feed

, and the DC power supplies

PEM2

and

PEM3

must be powered by dedicated power feeds derived

from feed

. This configuration provides the commonly deployed

A/B

feed

redundancy for the system.

NOTE:

For information about connecting to DC power sources, see

“DC

Power Supply Electrical Specifications for the MX480 Router” on page 301

Replace the clear plastic cover over the terminal studs on the faceplate.

10.

Route the power cables along the cable restraint toward the left or right corner of the
chassis. If needed to hold the power cables in place, thread plastic cable ties, which
you must provide, through the openings on the cable restraint.

233

Chapter 14: Replacing MX480 Hardware Components