HP StorageWorks 2405 - Disk System User Manual page 22

Power supplies share the load reciprocally; that is, each supply automatically
increases its output to compensate for reduced output from the other, and vice
versa. If one power supply fails, the other delivers the entire load.
Internal circuitry triggers a fault when the internal fan or other part fails. At the
same time, the power fault LED (amber) illuminates, and, if enabled, the
hardware event monitor sends an event message. The power supply fan remains
on if other parts fail in order to maintain cooling air flow through the system. If
the fan fails, the power supply shuts down. The fan in the other working power
supply will increase to full speed to compensate for the failed fan. The failed
power supply/fan module must be removed and the replacement power supply/
fan module installed within two minutes. In the event of a failure, if a
replacement fan module/power supply is not available, leave the failed power
supply/fan module installed until you are ready to replace it. This should be done
to maintain proper cooling for the disk system.
Internal circuitry senses fan motion and triggers a fault when the speed of the
power supply's internal fan falls below a critical level. At the same time, the LED
turns amber, and, if enabled, the hardware event monitor sends an event message.
22 Product Description