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 supply in PEM0 must be powered by dedicated
power feeds derived from feed A, and the DC power supply in PEM2 must
be powered by dedicated power feeds derived from feed B. This
configuration provides the commonly deployed A/B feed redundancy for
the system.
NOTE: For information about connecting to DC power sources, see “DC
PowerSupply ElectricalSpecifications for the MX240 Router” onpage143.
9. Replace the clear plastic cover over the terminal studs on the faceplate.
10. Verify that the power cabling is correct, that the cables are not touching or blocking
access to router components, and that they do not drape where people could trip on
them.
11. Verify that the INPUT OK LED on the power supply is lit green.
12. On each of the DC power supplies, switch the DC circuit breaker to the center position
before moving it to the on (—) position.
NOTE: The circuit breaker may bounce back to the off (O) position if you
move the breaker too quickly.
Observe the status LEDs on the power supply faceplate. If the power supply is correctly
installed and functioning normally, the PWR OK, BRKR ON, and INPUT OK LEDs light
green steadily.
259Copyright © 2017, Juniper Networks, Inc.
Chapter 21: Installing Components
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