IBM DS3500 Installation, User's, And Maintenance Manual page 151

Each power supply has a built-in sensor that detects the following conditions:
v Over-voltage
v Over-current
v Overheated power supply
If any of these conditions occurs, one or both power supplies will shut down. If
the power remains off (does not automatically restart), ensure that the environment
is optimal (no overheating has occurred, all electrical receptacles are working, and
so on). For more information, see "Restoring power after an unexpected
shutdown" on page 98.
If both power supplies fail or if the power supplies cannot maintain an internal
temperature below 65°C (149°F), the power supplies will automatically shut down
(an overtemperature condition). If this occurs, you must cool the storage subsystem
and restart it. See "Restoring power after an unexpected shutdown" on page 98.
Attention: The fans in the power supplies draw in fresh air and force out hot air.
The power supplies are hot-swappable and redundant; however, if the fans in one
power supply fail, you must replace the entire failed power supply within 72
hours to maintain redundancy and optimum cooling. Do not remove the failed
power supply until you have the replacement power supply. When you do remove
the failed power supply, be sure to install the second power supply within 10
minutes to prevent any overheating due to the interruption to the air flow that
cools the storage subsystem.
Do not run the storage subsystem without adequate ventilation and cooling,
because it might cause damage to the internal components and circuitry.
To replace a power supply, complete the following steps.
Attention: To prevent damage to the storage subsystem components from
overheating, replace a failed power supply within 10 minutes of removal. If
replacing it will take longer than 10 minutes, stop all I/O activity to the storage
subsystem and turn off the power until you complete the replacement. Do not
remove the failed power supply from the storage enclosure until you:
v Review the replacement procedure in this section.
v Have the replacement power supply and are ready to install it in the enclosure.
(L001)
1. If necessary, use the Storage Manager software to print a storage system
profile.
2. Read the safety information that begins on page "Safety" on page ix and "Best
practices guidelines" on page 8.
Chapter 5. Replacing components
133