WARNING: Before performing DC power procedures, ensure that power is removed
from 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.
You connect DC power to the router by attaching power cables from the external DC power sources to
the terminal on the power supply faceplate. You must provide the power cables (the cable lugs are supplied
with the router). For power cable specifications, see “DC Power Cable Specifications for MX204 Router”
on page 45.
To connect the DC source power cables to the router for each power supply:
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 grounding strap around your bare wrist, and connect the other
end of the strap to the ESD point on the chassis.
3. 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.
CAUTION: You must ensure that power connections maintain the proper polarity.
The power source cables might be labeled (+) and (–) to indicate their polarity. There
is no standard color coding for DC power cables. The color coding used by the external
DC power source at your site determines the color coding for the leads on the power
cables that attach to the terminal studs on each power supply.
4. Remove the screws from the terminals.
5. Secure each power cable lug to the terminal with the screws (see Figure 38 on page 97). Apply between
5 lb-in. (0.6 Nm) and 6 lb-in. (0.7 Nm) of torque to the screws. Do not overtighten the screws. (Use a
socket nut driver.)
a. Secure the positive (+) DC source power cable lug to the RTN (return) terminal.
96
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