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.
Guidelines for AC-Powered Systems
Basic guidelines for AC-powered systems include the following:
• Each chassis power supply should have its own dedicated branch circuit.
• The circuit breaker should be sized according to the power supply input rating and local or national code
requirements.
• The AC power receptacles used to plug in the chassis must be the grounding type. The grounding
conductors that connect to the receptacles should connect to protective earth ground at the service
equipment.
Prevent 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 such as the Cisco
ASR 920 Series Router, which can have substantial current-draw fluctuations due to bursty data traffic
patterns.
Determining power requirements is useful for planning the power distribution system needed to support the
router.
Preventing ESD Damage
This equipment needs to be grounded. Use a green and yellow 6 AWG ground wire to connect the host to
earth ground during normal use. Statement 383
Warning
Electrostatic discharge (ESD) can damage equipment and impair electrical circuitry. ESD may occur when
electronic printed circuit cards are improperly handled and can cause complete or intermittent failures. When
removing and replacing modules, always follow ESD prevention procedures:
• Ensure that the router chassis is electrically connected to earth ground.
Cisco ASR-920-12SZ-A and Cisco ASR-920-12SZ-D Aggregation Services Router Hardware Installation Guide
7
Safety Warnings
Guidelines for DC-Powered Systems
