Nortel Passport 15000, Установка и обслуживание оборудования, Страница: 100 / 874

100 Chapter 7 Cooling units
241-1501-240 5.2S2
Cooling unit replacement
Replace a cooling unit if it fails or to facilitate the replacement of cooling unit
parts.
• “Prerequisites to cooling unit replacement” (page 100)
• “Cooling unit replacement task flow” (page 101)
Prerequisites to cooling unit replacement
• You need one of the following versions of the cooling unit:
— NTHR51AA or NTHR51AB for a lower (rear) cooling unit
— NTHR52AA or NTHR52AB for an upper (front) cooling unit
• The PEC of the cooling units NTHR51AB and NTHR52AB is visible on
its mounting ear. The mounting ears are blank for the NTHR51AA and
NTHR52AA versions. To distinguish a lower cooling unit NTHR51AA
from an upper unit NTHR52AA, observe the cable connectors that are
only on the mounting ear of a lower cooling unit.
• The AA and AB versions of the cooling units are interchangeable, but
their parts are not.
• Get a helper to assist the removal and insertion of a cooling unit because
it weighs 9.1 kg (20 lbs) and has a tendency to slide out of position when
it is unfastened.
• Replacing an entire cooling unit is not necessary because of a part failure,
however, the task might be considered a safer method of working around
live fan blades or inside tight spaces or both. It should take less than 5
minutes to replace an entire cooling unit.
CAUTION
Service degradation or interruption by heat
When the cooling unit of an in-service Passport 15000 or
20000 loses power, the air temperature inside the shelf
rises rapidly. When the temperature inside a fabric exceeds
70 degrees Celsius (158 degrees Fahrenheit), that fabric
will automatically shut down until the temperature drops
below the threshold.