Fans; Fan Controllers; Air Filters - Nortel Passport 15000 Hardware Description

Fans

The fans push or pull air across the surfaces of the processor cards and
modules to keep them as cool as ambient room temperature allows. When a
fan is mounted in a lower (rear) cooling unit, it pushes air. When the same fan
is mounted in an upper (front) cooling unit, it pulls air.

Fan controllers

A fan controller controls the power supply to a fan, monitors the operation of
the fan and its speed, and monitors the status of the remote temperature
sensors. In the case of a failure, the controller sends an alarm signal to the
alarm/BITS module and sends a status signal to the other fans, forcing them
to switch to the higher rpm speed.
Air filters
The Passport 15000 or 20000 frame is equipped with air filters to prevent dust
and other airborne contaminants from being drawn into the shelf assemblies
by the cooling units. The filters also assist air flow by acting as air flow
diffusers. The air filter for the lower cooling unit is located at the bottom of
the frame. The air filter for the upper cooling unit is located in the middle of
the frame, between the upper cooling unit and the upper shelf assembly.
The figure "Upper and lower cooling unit in a frame with air flow direction"
(page 130) shows the location of the air filter. The air filter is the same part
number for all versions of cooling units.
The air filters must be installed in the frame assembly to ensure proper air
flow across the shelf assembly. The Passport 15000 or 20000 should not be
operated without air filters, except briefly during filter replacement. The fans
should remain powered while the filter is being replaced.
The air filters must also be changed periodically so that the accumulation of
dust is prevented from degrading performance or failing plug-in cards, fabric
cards, or modules. For information about the frequency of replacing air filters
and how to replace them, refer to 241-1501-240 Passport 15000, 20000
Hardware Installation, Maintenance and Upgrade in the chapter of safety
considerations and best practices, the section on equipment maintenance.
Passport 15000, 20000 Hardware Description
Chapter 3 Shelf assembly 133
5.2S2