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Power Supplies
Two temperature thresholds exist in Modular Chassis system
power supplies. In the event of a heat buildup beyond the lower
threshold within a monitored power supply, thermal protection
circuitry illuminates the Overtemperature LED on the front panel
of the Modular Chassis.
Note
If temperatures climb further, beyond the higher threshold of
maximum safe ratings, an
and the affected power supply is shut down automatically.
At the lower threshold, Motorola-supported SCSI devices in the
XR900 enclosure and most other SCSI devices are approaching their
upper temperature limits but are not in danger of immediate
damage. Several conditions can trigger the alarm:
A failed fan in a warm environment
Blocked airflow in or out of the enclosure
An ambient temperature near the specified limits of the
enclosure (50˚ C/122˚ F)
The Overtemperature LED turns off when the cooling problem is
corrected if the correction is made before the power supply sensor
warms another 5˚ F to system shutdown. Powering down to correct
a problem may not be necessary, because many failures are caused
by nothing more than inadvertent blockages of the airflow. Prompt
removal of a blockage allows recovery without a shutdown of
system power. In general, power should not be removed from the
system until a normal system shutdown is completed.
If the XR900 is the location of the overtemperature
condition, its Overtemperature LED also illuminates.
ACFAIL
Environmental Monitor
signal is placed on the VMEbus
3
3-3
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