Juniper MX480 Hardware Manual page 131

Copyright © 2011, Juniper Networks, Inc.
To connect the DC source power cables to the router:
Switch off the dedicated customer site circuit breakers. Ensure that the voltage across
1.
the DC power source cable leads is 0 V and that there is no chance that the cable
leads might become active during installation.
Attach an electrostatic discharge (ESD) grounding strap to your bare wrist, and connect
2.
the strap to one of the ESD points on the chassis.
Move the DC circuit breaker on the power supply faceplate to the off (
3.
Remove the clear plastic cover protecting the terminal studs on the faceplate.
4.
Verify that the DC power cables are correctly labeled before making connections to
5.
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 and DC cables to chassis ground:
–48V RTN
The cable with very large resistance (indicating an open circuit) to chassis ground
is .
–48V
The cable with very low resistance (indicating a closed circuit) to chassis ground is
.
RTN
CAUTION: You must ensure that power connections maintain the proper
polarity. The power source cables might be labeled
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.
Remove the nut and washer from each of the terminal studs. (Use a 7/16-in. [11 mm]
6.
nut driver or socket wrench.)
Secure each power cable lug to the terminal studs, first with the flat washer, then
7.
with the nut (see Figure 64 on page
(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 each positive (+) DC source power cable lug to the
b. Secure each negative (–) DC source power cable lug to the
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.
Chapter 10: Grounding and Providing Power to the MX480 Router
102). Apply between 23 lb-in. (2.6 Nm) and 25 lb-in.
) position.
O
and to indicate
(+) (–)
(return) terminal.
RTN
(input) terminal.
–48V
101