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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 the 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 terminals are correctly labeled. As shown in Figure 2-8, the correct labeling
of the terminals is with – (negative polarity) on the left and + (positive polarity) on the 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 terminal and positive polarity on 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 and fasten with the screw for that terminal.
1On newer power supplies, the left terminal is
labeled for negative polarity. Connect the
negative cable to this left-side terminal.
3On the originally released power supplies, the
left terminal has negative polarity but is
labeled as +. Connect the negative cable to
this left-side terminal.
2On newer power supplies, the right terminal is
labeled for positive polarity. Connect the
positive cable to this right-side terminal.
4On the originally released power supplies, the
right terminal has positive polarity but is
labeled as –. Connect the positive cable to this
right-side terminal.
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