Replacing an MX240 DC Power Supply Cable

1. Disconnecting an MX240 DC Power Supply Cable
2. Connecting an MX240 DC Power Supply Cable

Disconnecting an MX240 DC Power Supply Cable

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.

To disconnect a power cable for a DC power supply:

1. Switch off the dedicated customer site circuit breaker for the power supply being removed. Follow your site's procedures for ESD.
2. Make sure that the voltage across the DC power source cable leads is 0 V and that there is no chance that the cables might become active during the removal process.
3. Verify that the INPUT OK LED on the power supply is not lit.
4. Remove the power cable from the external DC power source.
5. Attach an electrostatic discharge (ESD) grounding strap to your bare wrist, and connect the strap to one of the ESD points on the chassis.
6. Switch the DC circuit breaker on the DC power supply faceplate to the off (O) position.
7. Remove the clear plastic cover protecting the terminal studs on the faceplate.
8. Remove the nut and washer from each of the terminal studs. (Use a 7/16-in. [11 mm] nut driver or socket wrench.)
9. Remove the cable lug from the terminal studs.
10. Carefully move the power cable out of the way.

Connecting an MX240 DC Power Supply Cable

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.

To connect a power cable for a DC power supply:

1. Locate a replacement power cable that meets the specifications.
2. Verify that a licensed electrician has attached a cable lug to the replacement power cable.
3. Verify that the INPUT OK LED is off.
4. Secure the power cable lug to the terminal studs, first with the flat washer, then with the nut. Apply between 23 lb-in. (2.6 Nm) and 25 lb-in. (2.8 Nm) of torque to each nut (see Figure 1). Do not overtighten the nut. (Use a 7/16-in. [11 mm] torque-controlled driver or socket wrench.)

   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 onto the terminal stud. The nut should be able to spin freely with your fingers when it is first placed onto the terminal stud. Applying installation torque to the nut when improperly threaded may result in damage to the terminal stud.

   Caution: The maximum torque rating of the terminal studs on the DC power supply is 36 lb-in. (4.0 Nm). The terminal studs may be damaged if excessive torque is applied. Use only a torque-controlled driver or socket wrench to tighten nuts on the DC power supply terminal studs.

   Figure 1: Connecting Power Cables to the DC Power Supply

   
5. Verify that the DC power cable is connected correctly, that it does not touch or block access to router components, and that it does not drape where people could trip on it.
6. Replace the clear plastic cover over the terminal studs on the faceplate.
7. Attach the power cable to the DC power source.
8. Turn on the dedicated customer site circuit breaker to the power supply.
9. Verify that the INPUT OK LED on the power supply is lit steadily.
10. On each of the DC power supplies, switch the DC circuit breaker to the center position before moving it to the on (—) position.

    Note: The circuit breaker may bounce back to the off (O) position if you move the breaker too quickly.

    Observe the status LEDs on the power supply faceplate. If the power supply is correctly installed and functioning normally, the PWR OK, BRKR ON, and INPUT OK LEDs light green steadily.