Juniper T640 Hardware Manual page 266

T640 Core Router Hardware Guide
232
CAUTION: Do not use a terminal jumper for 60-A DC power cables. Using a
terminal jumper is not supported for this procedure. Doing so will cause a
short across the inputs and trip your external circuit breaker.
CAUTION: All connected inputs on the DC power supply in slot PEM0 must
be powered by dedicated power feeds derived from feed A, and all connected
inputs on the DC power supply in slot PEM1 must be powered by dedicated
power feeds derived from feed B. This configuration provides the commonly
deployed A/B feed redundancy for the system.
CAUTION: You must use an appropriate torque-controlled tool to tighten
the nuts. Applying excessive torque damages the terminal studs and the
power supply. The absolute maximum torque that may be applied to this nut
is 45 lb-in. (5.0 Nm).
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.
NOTE: We recommend that the positive (+) DC source power cables to be
connected to the RTN (return) terminals be 2.6 in. (6.6 cm) longer than the
negative (–) DC source power cables to be connected to the –48 V (input)
terminals.
To connect five 60-A DC source power cables to the router, follow this procedure for
each DC power supply:
Verify that a properly rated customer site circuit breaker for each DC power cable has
1.
been installed. See the DC power electrical safety guidelines for your router for more
information.
Switch off the customer site circuit breakers. Ensure that the voltage across the DC
2.
power source cable leads is 0 V and that there is no chance that the cable leads might
become active during installation.
and to indicate
(+) (–)
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