IBM DS4200 Installation, User's, And Maintenance Manual page 150

replaceable units (CRUs) and do not require preventive maintenance. Use only the
supported power supply and fan units for your specific storage subsystem.
Each power supply and fan unit 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 after the condition that causes it to go off, make sure that the
environment is optimal (no overheating has occurred, all electrical outlets are
working, and so on). For more information, see "Restoring power after an
unexpected shutdown" on page 97.
The storage subsystem cooling system consists of two fans in each of the two
power supply and fan unit CRUs. The power supply and fan units circulate air from
the front to the back of the unit.
If both power supply and fan units fail, or if the power supply and fan units cannot
maintain an internal temperature below 70° C (158° F), the power supply and fan
units will automatically shut down (an over-temperature condition). If this occurs,
you must cool the unit and restart it. See "Restoring power after an unexpected
shutdown" on page 97.
Attention:
out hot air. The power supply and fan units are hot-swappable and redundant;
however, if the fans in one power supply and fan unit fail, you must replace the
entire failed power supply and fan unit within 72 hours to maintain redundancy and
optimum cooling. Do not remove the failed power supply and fan unit until you have
the replacement power supply and fan unit. When you do remove the failed power
supply and fan unit, be sure to install the second power supply fan and unit 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.
Use the following procedure to replace a power supply and fan unit. Figure 77 on
page 127 illustrates removing and inserting a unit.
Attention:
overheating, replace a failed power supply and fan unit CRU within 15 minutes of
removal. If replacing it will take longer than 15 minutes, stop all I/O activity to the
storage subsystem and turn off the power until you complete the replacement.
Statement 8:
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IBM System Storage DS4200 Express Storage Subsystem: Installation, User's and Maintenance Guide
The fans in the power supply and fan units draw in fresh air and force
Potential damage to a component - To prevent damage from