Adding, Removing, or Replacing a DC-Input Power Supply
To add a second (redundant) DC-input power supply to the router, perform the following steps:
Step 1 Locate the source DC circuit breaker that will service the DC-input power supply; ensure that this circuit breaker is set to the OFF position. For added safety, tape the circuit breaker handle in the OFF position.
Note The color coding scheme used for the source DC power cables for the DC-input power supply depends on the scheme used for the site DC power source. Typically, green or green/yellow is used for earth ground, red is used for positive (+), and black is used for negative (–). Make certain that you properly map the color coding scheme used at the site for the DC power source to the proper terminals on the DC-input power supply faceplate.
Warning To be completely sure that power has been removed from the source DC circuit that will be used to service the new power supply, use a voltmeter to measure the voltage across the negative (–) and positive (+) source DC leads to be connected to the power supply. Set the voltmeter to a range that makes it capable of measuring up to 75 VDC. The measurement across the positive and negative leads should be zero (0) volts.
Step 2 Using a 1/4-inch flat-blade screwdriver, loosen the captive installation screw on the blank filler panel covering the vacant (upper) power supply bay; remove the filler panel and retain it for possible future use.
Presumably, you will be installing the new power supply in the upper power supply bay, since, by convention, a single DC-input power supply is installed in the lower bay.
Step 3 Ensure that the rotary power switch on the faceplate of the new power supply that you will be installing is set to the OFF (O) position.
Step 4 Grasp the carrying handle on the new power supply with your left hand; while lifting the power supply, place your right hand beneath the unit to support its weight.
7-22Cisco 12008 Gigabit Switch Router Installation and Configuration Guide
