Removing the Circuit Breaker Box

The circuit breaker box is located on the rear of the chassis above the right power supply, as shown in Figure 2. It weighs about 6 lb (2.7 kg).

Do not remove the grounding lug from the grounding points on the chassis during this procedure.

To remove the circuit breaker box, follow this procedure (see Figure 99):

1. On the console or other management device connected to the master Routing Engine, enter CLI operational mode and issue the following command to shut down the router software. (If two Routing Engines are installed, also issue the command on the backup Routing Engine.)
   user@host> request system halt

   Wait until a message appears on the console confirming that the operating system has halted.

   For more information about the command, see the JUNOS Protocols, Class of Service, and System Basics Command Reference.

2. For each power supply, press the power switch on the circuit breaker box to the OFF (O) position.

   If you are power cycling the power supply rather than shutting it off for a time, wait at least 60 seconds after turning it off before turning it back on. If you need to power it off again, wait for at least 60 seconds after powering it on.

3. Shut off the power flowing from both external power sources, so that the voltage across the leads of the power cables is 0 V. Ensure that there is no chance that the cable leads might become active during the procedure.
4. Attach an electrostatic discharge (ESD) grounding strap to your bare wrist and connect the strap to one of the ESD points on the chassis. Make sure the router is attached to a proper earth ground. For more information about ESD, see Preventing Electrostatic Discharge Damage.
5. Using a Phillips screwdriver, loosen and remove the screws securing the protective shield over the terminal studs on the circuit breaker box. Remove the cover.
6. Using a 7/16-in. nut driver or wrench, loosen the outer nut securing the cable lug to each terminal stud. Remove the outer nuts and washers, leaving the inner nut and washer on each stud.

   Do not substitute a metric nut driver or wrench. A tool that does not fit the nuts exactly can damage them. If a 7/16-in. tool is not available, use pliers or an adjustable wrench.

7. Slide the cable lug off of each terminal stud. Leave the inner washer and nut on each stud.
8. Remove the rear lower impeller assembly by loosening the thumbscrew at each corner and pulling the impeller assembly straight out of the chassis. For complete instructions, see Removing the Rear Lower Impeller Assembly.
9. Using a Phillips screwdriver, loosen and remove the screw at each corner of the circuit breaker box. Loosen the thumbscrews at the top and bottom edge of the box.
10. Pull the circuit breaker box straight out of the chassis.