Cisco Systems MGX 8220 Cooling Assembly

2-6
Cisco MGX 8220 Installation and Configuration
Release 5.0, Part Number 78-6430-03 Rev. D0, November 2003
Chapter
Cooling Assembly
DC Power Drain and Circuit Protection
Each card in an Cisco MGX 822 0 sh el f draw s an averag e o f 2 1W with a worst-case shelf current o f
14.40A.
The circuit breaker in the DC power entry module (PEM) is rated at 15.00A.
The Cisco MGX 8220 circuits are p rot ect ed as follows:
•Backplane has a 5A fast-blow fuse f o r eac h s lot p o s it io n.
•Each board has a 1.5A c ircuit breaker in the - 4 8V DC line to the DC/D C converter.
Each Cisco MGX 8220 board is equipped with a DC/DC converter (Shindengen—HGG05006 or
AT&T —JW030A), which has an automatic current limited to 5V output.
A schematic of the DC power system is shown in Figure2-6.
Figure2-6 DC Power System
Cooling Assembly
This section describes the cooling assembly that cools the Cisco MGX 8220 shelf and equipment:
•Main Cooling Assembly, page 2-7
•Booster Cooling Assembly, page 2-8
•Plenum Exhaust Chamber, page 2-8
•Spacer Unit, page 2-8
•Cooling Assembly Power, page 2-8
The main cooling unit houses the fans that circulate air through the shelf. This unit is mounted below
the shelves. This unit is capable of cooling up to two Cisco MGX 8220 shelves in the same rack. Racks
that contain more th an tw o shelves require a bo oster unit to provide a dd itional cooling. The c oo ling
assembly is powered from the main shelf.
The plenum or a spacer unit is mounted above the shelves to exhaust the warm air.
A single Cisco MGX 8220 shelf is shown in Figure2-7. For more information on rack assembly and
configuration, see Chapter 7, “Installatio n and Start- Up .”
PEM
B
A
C
K
P
L
A
N
E
Battery
power
-48V
RTN
Safety
ground
-48V -48V
RTN RTN DC/DC
converter
Conductive edge
Circuit board
Earth ground
Safety ground
H8248