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Cisco Nexus 3000 Series Hardware Installation Guide
OL-25338-04
Chapter 2 Installing the Cisco Nexus 3000 Series Switches
Starting the Switch
Step 5 If you are installing a switch with a DC power supply, connect the power supply to a DC power source
as follows:
a. Verify that the DC power source is turned off at t he circuit breaker.
b. Remove the clear plastic safety cover that prevents you from touching the negative (-) and positive
(+) terminals on the power supply.
c. Determine whether the termina ls are correctly labeled. As s hown in Figure 2-8, the correct labeling
of the terminals is with – (negative polarity) on the left and + (positive polarity) on th e right (see
Callouts 1 and 2), and the incorrect labeling is with + on the left and – on the right (see Callouts 3
and 4).
Note All DC power supplies have negative polarity on the left te rminal and positive polarity o n the
right terminal but early manufactured versions of these power supplies were labeled with + on
the left and – on the right.
Figure 2-8 Polarity Labeling of DC Power Supply Terminals (Current and Early Labeling)
d. Connect a negative cable from the power source to the left terminal (is labeled - on newer power
supplies [see Callout 1 in Figure 2-8] and + on the first power supplies sold [see Callout 3 in
Figure 2-8]) on the power supply a nd fasten with the screw fo r that terminal.
1On newer power supplies, the left terminal is
labeled for negative polar ity. Connect the
negative cable to this left-side t erminal.
3On the originally released power sup plies, the
left terminal has nega tive polarity but is
labeled as +. Connec t the negative cable to
this left-side terminal.
2On newer power supplies, the right terminal is
labeled for positive pol arity. Connect the
positive cable to this right- side terminal.
4On the originally released power sup plies, the
right terminal has positive p olarity but is
labeled as –. Connect the positive cabl e to this
right-side terminal.
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