• Phillips (+) screwdriver, number 2
• A multimeter
You can install up to two DC power supplies in an EX9251 switch. The DC power supply in an EX9251
switch is a hot-removable and hot-insertable field-replaceable unit (FRU). You can remove and replace it
while the switch is running without turning off power to the switch or disrupting switching functions.
The power supplies install in the slots on the rear panel of the chassis.
CAUTION: Do not mix AC and DC power supplies in the same chassis.
WARNING: Before you perform DC power procedures, ensure there is no power to the
DC circuit. To ensure that all power is off, locate the circuit breaker on the panel board
that services the DC circuit, switch the circuit breaker to the off position, and tape the
switch handle of the circuit breaker in the off position.
CAUTION: Before you connect power to the switch, a licensed electrician must attach
cable lugs 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).
NOTE: Each power supply input feed must be connected to a dedicated DC power source outlet.
To connect DC power to an EX9251 switch (see
):
1.
Switch off the dedicated customer site circuit breakers. Ensure that the voltage across the DC
power source cable leads is 0 V and that there is no chance that the cable leads might become
active during installation.
2.
Wrap and fasten one end of the ESD wrist strap around your bare wrist, and connect the other end
of the strap to the ESD point on the switch.
3.
Remove the plastic cover from the terminal block on the power supply faceplate.
4.
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 large resistance (indicating an open circuit) to chassis ground is –48V.
• The cable with very low resistance (indicating a closed circuit) to chassis ground is RTN.
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