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Cisco ASR 903 Router Hardware Installation Guide
OL-25178-05
Chapter3 Installing the Cisco ASR 903 Router
Installing the Power Supply
Preventing Power Loss
Use the following guidelines to prevent power loss to the router.
•To prevent loss of input power, ensure that the total maximum load on each circuit supplying the
power supplies is within the current ratings of the wiring and breakers.
•In some systems, you can use an UPS to protect against power failures at your site. Avoid UPS types
that use ferroresonant technology. These UPS types can become unstable with systems like the
Cisco ASR 903 Router, which can have substantial current draw fluctuations due to bursty data
traffic patterns.
Use the information in the “DC Power Specifications” section on page1-4 to estimate the power
requirements and heat dissipation of a CiscoASR 903 Router based on a given configuration of the
router. Determining power requirements is useful for planning the power distribution system needed to
support the router.
Power Connection Guidelines
This section provides guidelines for connecting the CiscoASR 903 Router power supplies to the site
power source.
Warning
Never defeat the ground conductor or operate the equipment in the absence of a suitably installed
ground conductor. Contact the appropriate electrical inspection authority or an electrician if you are
uncertain that suitable grounding is available.
Statement 213
Warning
The plug-socket combination must be accessible at all times because it serves as the main
disconnecting device.
Statement 1019
Warning
This product requires short-circuit (overcurrent) protection, to be provided as part of the building
installation. Install only in accordance with national and local wiring regulations.
Statement 1045

Guidelines for DC-Powered Systems

Basic guidelines for DC-powered systems include the following:
•Each chassis power supply should have its own dedicated input power source. The source must
comply with the safety extra-low voltage (SELV) requirements in the UL 60950, CSA 60950, EN
60950, and IEC 60950 standards.
•The circuit must be protected by a dedicated two-pole circuit breaker. The circuit breaker should be
sized according to the power supply input rating and local or national code requirements.
•The circuit breaker is considered the disconnect device and should be easily accessible.
•The system ground is the power supply and chassis ground.
•Do not connect the DC return wire to the system frame or to the system grounding equipment.
•Use the grounding lug to attach a wrist strap for ESD protection during servicing.