EXFO QA-805 - Manual (Page 17)

Introduction
QualityAssurer 805 9
Cooling Assembly
Cooling Assembly
Fan Tray
There are 2 fan tray cassettes in the system. The cooling is performed side
to side. While the fan tray is a single mechanical block, it has 2 functions:
front board cooling and RTM cooling. The front and rear blanks are
necessary for proper airflow.
The fan tray contains electronics such that it is detected as a fully PICMG
compliant IPMC by the shelf manager. It contains hot-swap circuitry,
common fusing, fan supervising, and control circuitry.
The system utilizes push pull cooling with 2 separately managed fan trays
and 4 independent cooling zones. Integrated power supplies enable using
48 V fans without any degradation in performance under 90 – 264 V.
Under normal operating conditions the shelf manager cooling algorithm
sets the fan speed to an acceptable level.
The cooling algorithm works based on temperature events coming from
FRUs. Fan speed in a particular cooling zone will be increased if any FRU in
that zone reports a temperature crossing non-critical threshold. For safety
reasons, if any FRU reports a temperature crossing critical threshold, the
fan speed in all cooling zones will be increased.