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 nuts from the terminals.
5. Secure each power cable lug to the terminal with the nuts (see Figure 28 on page 99). Apply between
5 lb-in. (0.6 Nm) and 6 lb-in. (0.7 Nm) of torque to the nuts. Do not overtighten the nuts. (Use a socket
nutdriver.)
a. Secure the positive (+) DC source power cable lug to the RTN (return) terminal.
b. Secure the negative (–) DC source power cable lug to the –48V (input) terminal.
CAUTION: Ensure that each power cable lug seats flush against the surface of the
terminal block as you are tightening the nuts. Ensure that each nut is properly
threaded into the terminal. Applying installation torque to the nuts when improperly
threaded can result in damage to the terminal.
98
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