Cisco MGX 8950 Installation Manual page 32

Installation Procedures
Use four mounting screws and a Phillips-head screwdriver to bolt the exhaust plenum in the rack. See
Step 4
Figure 3-4
Install the DC PEM(s)
Before performing any of the following procedures, ensure that power is removed from the DC
Warning
circuits. To ensure that all power is removed, locate the circuit breakers or fuses on the DC power
lines that service the DC circuits. Turn OFF the DC power line circuit breakers and remove the DC
power line fuses.
Before working on a system that has an On/Off switch, turn OFF the power and unplug the power cord.
Warning
Never install an AC power module and a DC power module in the same chassis.
Warning
Warning Before working on a chassis or working near power supplies, unplug the power cord on AC units;
disconnect the power at the circuit breaker on DC units.
For a DC-powered system, install the DC PEMs at the back of the air intake plenum. If you install only
one DC-PEM, install it on the bottom as viewed from the rear of the plenum. (See
Figure 3-15 DC-PEMs Installed in Back of the Air Intake Module
Cisco MGX 8950 Hardware Installation Guide
3-32
for the correct placement of the exhaust plenum.
Secondary PEM
-48 V DC
50A RT N
-48 V
-48 V DC
50A
J1
-48 V DC
RT N
50A
-48 V
-48 V DC
50A J1
Primary PEM
J2
RT N
-48 V
-48 V DC
50A
DC
J2
RT N
-48 V
-48 V DC
50A
DC
Release 3, Part Number 78-14147-02 Rev. A0, November 2002
Chapter 3 Installing a Cisco MGX 8950
Figure 3-15.)