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Catalyst 4500 E-Series Switches Installation Guide
OL-13972-01
Chapter 2 Preparing for Installation
Power Connection Guidelines for DC-Powered Systems
Power Connection Guidelines for DC-Powered Systems
This section provides the basic guidelines for connecting the Catalyst 4500 E-series switch compatible
DC-input power supplies to the site power source or AC power shelf:
• All power connection wiring should conform to local and national codes.
• DC (–) and DC return (+) terminals are evaluated for use with 1/0 AWG wire (1400W DC supply
only).
• The ground terminal is evaluated for use with 6 AWG wir e (10 AWG for the multi-input power
supply).
• DC (–) and DC return (+) wire lugs shall not exceed 0.83 inches in width (0.378 inches for the
multi-input power supply).
• For DC power cables, we recommend that you use commensurately rated, high-strand-count copper
wire cable. Connection to the DC-input power supply requires one earth ground cable, one source
DC (–), and one source DC return (+). The length of the cables depends on your switch location.
These cables are not available from Cisco Systems. They are available from any commercial cable
vendor.
• The color coding of the source DC power cable leads depends on the color coding of the site DC
power source. Typically, green or green and yellow indicate that the cable is a ground cable. Because
there is no color code standard for source DC wiring, you must ensure that the power cables are
connected to the DC-input power supply terminal block in the proper (+) and (–) polarity. In some
cases, the source DC cable leads might have a positive (+) or a negative (–) label. This label is a
relatively safe indication of the polarity, but you must verify the polarity by measuring the voltage
between the DC cable leads. When making the measurement, the positive (+) lead and the negative
(–) lead must always match the (+) and (–) labels on the DC-input power supply terminal block.
Calculating DC Input Current
Complete power usage tables are in the Catalyst 4500 Series Module Installation Guide. To calculate the
DC input current needed for data and inline power applications, use the following steps (the example
shows the DC input current requirement in a Catalyst 4503-E with a Supervisor Engine II and two
WS-X4306-GB modules, and assumes a DC input voltage of -48
VDC):
Step 1 Add the power requirement for each component in your system.
• Catalyst 4503-E uses 54 W
• Supervisor Engine II+ uses 147 W
• WS-X4306-GB uses 2 X 47 = 94 W
• Total DC input power = 295 W
Step 2 After the entries for all components have been added together, divide that number by the DC input
voltage to determine the DC input current.
• Input current = 295 W/48 VDC = 6.14 A for data only.
Step 3 to Step 5 are for applications requiring inline power. If your configuration does not include inline
power devices, the DC input current is the result of Step 2.
Step 3 If you want to add an inline-capable module (WS-X4148-RJ45V) with 10 inline devices (such as IP
Phones) to your system, calculate the DC output power sent to inline devices.
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