5-77

Cisco MGX 8800/8900 Series Hardware Installation Guide
Releases 2 - 5.2, Part Number OL-4545-01, Rev. H0, May 2006
Chapter5 Installing the Cisco MGX Switch or Gateway
Installing the MGX 8950 Switch
Step4 If you are installing the exhaust plenum in a 19-inch cabinet, attach the rear-mounting brackets to the

rack, and use screws to secure the fan tray to the rear-mounting brackets.

Install the DC PEM(s)
Warning
Before performing any of the following procedures, ensure that power is removed from the DC
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.
Statement 322
Warning
Before working on a system that has an On/Off switch, turn OFF the power and unplug the power cord.
Statement 1
Warning
Never install an AC power module and a DC power module in the same chassis.
Statement 264
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.
Statement 12

For a DC-powered system, install the DC PEMs at the back of the air intake plenum. Tighten the captive

screws to attach the DC PEM to the component.

If you install only one DC-PEM, install it on the bottom, as viewed from the rear of the air intake plenum.

(See Figure 5-44.)

Figure5-44 DC PEMs Installed Behind the Air Intake Plenum
-48V DC 50A
DC
DC
-48V DC 50A
-48V
RTN
J2
J1
-48V DC 50A
-48V
RTN
-48V DC 50A-48V DC 50A
-48V
RTN
J2
J1
-48V DC 50A
-48V
RTN
43975
Secondary PEM
Primary PEM