NOTE: The battery returns of the DC power supply must be connected as an isolated DC return
(DC-I).
Before you begin connecting DC power to the switch:
•
Ensure that you have taken the necessary precautions to prevent electrostatic discharge (ESD) damage
(see “Prevention of Electrostatic Discharge Damage” on page 242).
•
Ensure that you have connected the switch chassis to earth ground.
CAUTION: Before you connect power to the switch, a licensed electrician must
attach a cable lug to the grounding and power cables that you supply. A cable with
an incorrectly attached lug can damage the switch (for example, by causing a short
circuit).
To meet safety and electromagnetic interference (EMI) requirements and to ensure
proper operation, you must connect the chassis to earth ground before you connect
it to power. For installations that require a separate grounding conductor to the
chassis, use the protective earthing terminal on the switch chassis to connect to the
earth ground. For instructions on connecting earth ground, see “Connecting Earth
Ground to a QFX5100 Device” on page 284.
•
Install the power supply in the chassis. For instructions on installing a power supply in a QFX5100 device,
see “Installing a Power Supply in a QFX5100 Device” on page 430.
Ensure that you have the following parts and tools available:
•
DC power source cables (14–16 AWG) with ring lug (Molex 190700069 or equivalent) (not provided)
•
Phillips (+) screwdriver, number 2 (not provided)
•
Multimeter (not provided)
To connect DC power to a QFX5100 device:
1. Attach the grounding strap to your bare wrist and to a site ESD point.
2. Verify that the DC power cables are correctly labeled before making connections to the power supply.
In a typical power distribution scheme where the return is connected to chassis ground at the battery
plant, you can use a multimeter to verify the resistance of the –48V and RTN DC cables to chassis
ground:
•
The cable with very low resistance (indicating a closed circuit) to chassis ground is positive (+) and
will be installed on the V+ (return) DC power input terminal.
289
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