Juniper MX2020 Hardware Manual page 158

MX2020 3D Universal Edge Router Hardware Guide
132
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.
NOTE: If the PSMs are installed in the router, make sure the power switches
on all PSMs are turned to the off (
Move the DC circuit feed switch on the PDM faceplate to match the current rating
3.
amperage— , or
60 A 80 A
NOTE: The switch position applies to all inputs of this PDM, and that
selecting the 60A position may reduce power output capacity available
from each PSM.
Loosen the captive screws on the plastic cable restraint on the lower edge of the
4.
power faceplate. The cable restraint is set on hinges that hold the cover in place during
cable installation.
NOTE: You can remove the plastic cover can be removed for DC power
cable installation by bending the plastic cable restraint cover until the two
plastic pins on both sides of the housing unhinge.
Verify that the DC power cables are correctly labeled before making connections to
5.
the PDM. 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 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 DC PDM.
Remove the cover protecting the terminal studs on the faceplate.
6.
) position.
O
for each feed.
(+) and (-) to indicate
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