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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 (1 0 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-co unt copper
wire cable. Connection to the DC-input power supply requires on e earth ground cable, one source
DC (–), and one source DC return (+). The length of the c ables 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 d epends 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 G uide. 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 toge ther, 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.