If Dc Power Supplies Are Installed - Cisco CDE 220 Series Hardware Installation Manual

Chapter 2 Preparing to Install the Content Delivery Engines
Safety Guidelines
Overcurrent protection: The CDE is designed for an AC line voltage source with up to 20 A of
overcurrent protection per cord feed. If the power system for the equipment rack is installed on a branch
circuit with more than 20 A of protection, you must provide supplemental protection for the CDE. The
overall current rating of a configured CDE is less than 6 A.

If DC Power Supplies Are Installed

Connection with a DC source should only be performed by trained service personnel. The CDE with DC
input is to be installed in a Restricted Access Location in accordance with articles 110-16, 110-17, and
110-18 of the National Electric Code, ANSI/NFPA 70. The DC source must be electrically isolated by
double or reinforced insulation from any hazardous AC source. The DC source must be capable of
providing up to 900 watts of continuous power per feed pair.
Do not apply AC power to DC power modules.
Caution
As a general rule, take precautions when preparing DC power cables for connection to the CDE. Make
sure to strip the power conductor insulation so that when installed, no external bare copper is accessible
at the terminal block. The torque required for the DC input terminal block connection on the power
supplies is 5 to 7 in-lb. Take precautions when connecting the polarity. The DC power input terminals
are marked as –48 V and RTN. The –48 V terminal is for the Negative (source DC –48 V or –60 V) and
the RTN is for the Positive (source DC return). After power cables have been installed, be careful to
avoid strain on the power connection. It is recommended that strain relief be provided as appropriate.
For example, route the power cables in the rack and secure the cables with nylon tie wraps.
Source DC power disconnect— You are responsible for installing a properly rated DC power disconnect
for the CDE system. This source disconnect must be readily accessible, and it must be labeled as
controlling power to the CDE. The circuit breaker of a centralized DC power system may be used as a
disconnect device when easily accessible and should be rated no more than 30 A.
Grounding the CDE— The ground connection must be made first and prior to powering the equipment.
Each power module is provided with a ground connection using the 5-mm screw. The connection is to
use a closed-loop lug and the screw is to be tightened to a torque of 6 to 8 in-lb. It is recommended that
the ground wire be number 12 to number 10 AWG, with green/yellow insulation, rated minimum 167°F
(75°C), low smoke fume (LSF) and flame retardant.
A supplemental ground connection is provided on the CDE in case it is intended for installation with an
isolated DC return (DC-I) and is to be installed in a Common Bonding Network (CBN) per NEBS
GR-1089. To reliably ground the CDE to the rack when rack-mounted, connect an additional grounding
conductor to the CDE using the separate listed closed two-hole crimp lug having 5/8-inch pitch. It is
recommended that the grounding conductor wire be number 12 to number 10 AWG, with green
insulation, rated minimum 75°C (167°F), low smoke fume (LSF), and flame retardant. The ground
connections should be tightened with a torque of 6 to 8 in-lb. The metal pin of each module near the input
power connector is to be connected to a protective earthing conductor during final system assembly.
Overcurrent protection— Overcurrent protection circuit breakers must be provided as part of each host
equipment rack and must be incorporated in the field wiring between the DC source and the CDE. The
branch circuit protection should be connected to a 30 A UL listed circuit breaker (or suitably certified
for the country used), rated minimum 75 VDC, and copper wire conductors, sized for 24 A current
(12 AWG).
Cisco Content Delivery Engine 205/220/250/280/285/420/460/475 Hardware Installation Guide
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