Juniper Networks MX480 - Manual (Page 327)

customer site circuit breaker rated for 40 A (–48 VDC) minimum, or as required by local
code. If you plan to operate a maximally configured DC-powered router with high-capacity
power supplies, we recommend that you use a circuit breaker rated for 70 A (–48 VDC),
or as required by local code.
If you plan to operate a DC-powered router at less than the maximum configuration, we
recommend that you provision a circuit breaker according to respective National Electrical
Code and customer site internal standards to maintain proper level of protection for the
current specified above or each DC power supply rated for at least 125% of the continuous
current that the system draws at –48 VDC.
Related
Documentation
DC Power Supply Electrical Specifications for the MX480 Router on page 301 •
• Calculating Power Requirements for MX480 Routers on page 285
DC Power Source Cabling and Cable Specifications for the MX480 Router
• DC Power Source Cabling for the MX480 Router on page 303
• DC Power Cable Specifications for the MX480 Router on page 304
DC Power Source Cabling for the MX480 Router
Figure 131 on page 303 shows a typical DC source cabling arrangement.
Figure 131: Typical DC Source Cabling to the Router
The DC power supplies in PEM0 and PEM1 must be powered by dedicated power feeds
derived from feed A , and the DC power supplies in PEM2 and PEM3 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 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.
303 Copyright © 2013, Juniper Networks, Inc.
Appendix D: Power Guidelines, Requirements, and Specifications for the MX480 Router