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Cisco MGX 8220 Installation and Configuration
Release 5.0, Part Number 78-6430-03 Rev. D0, November 2003
Chapter
Cooling Assembly
Booster Cooling Assembly
The booster cooling assembly is used in racks with more than two Cisco MGX 8220 shelves. It is
mounted above the shel ve s co ntaining the main co ol ing assembly and be low th e sh elves to which the
booster cooling is t o be provided. The boo ster cooling assembl y consists of fans th at draw air from the
shelves below and exhau s t air upward through the s h el f or shelves above. Eac h b oo ster supports an
additional two Cisco M G X 8220 shelves.
The booster cooling assembly measures
•3.5 inches (2 mounti ng u nits) high
•17.45 inches wide
•22 inches deep
Plenum Exhaust Chamber
The plenum exhaust chamber is used i n i n stal lat io n s whe re th e top of the unit must be enclosed. Th e
plenum chamber is mo unted in the rack imm ediately above the shel f or shelves. The chamb er exhausts
air from the shelf to the rear of th e r ac k. Th e p l enu m chamber is the exhaust option reco m me nd ed by
Cisco Systems.
The exhaust plenum chamber measures
•3.5 inches (2 mounti ng u nits) high
•17.45 inches wide
•22 inches deep
Spacer Unit
The spacer unit is an alternative metho d f or ex ha ust in g air fr om the rack and can take the place of t he
exhaust plenum. The spacer does not support the attachm e nt of a cable manage m en t ki t. If u sed, the
spacer unit is mounted in the r ac k i m me di ate ly above the shelf or shelves.
The spacer unit measures
•1.75 inches (1 mounting unit) high
•17.45 inches wide
•22 inches deep
Cooling Assembly Power
Power is supplied to a connector at the rear of the cooling assemblies by a cable running from the
bottom middle rear of the Cisco MGX 8220 shelf.
The assemblies provide output signals to the shelf. Using these signals, the cooling assembly
performance can be monitored by t he B NM car d s. Th e cab le delivering DC power to the cooling
assembly from the Cisco MGX 8220 shelf also carries these signals to the BNM using the backplane.
The signals are such that the model of cooling assem bly can be identified and the speed of each fan can
be monitored. Each fa n generates a fixed num b e r o f s qu ar e - w ave pu ls e s per revolution, allowing the
speed of the fan to be determined.