IBM DS3500 Installation, User's, And Maintenance Manual page 143

CAUTION:
To reduce the risk of electric shock or energy hazards:
v This equipment must be installed by trained service personnel in a restricted-access location, as
defined by the NEC and IEC 60950-1, First Edition, The Standard for Safety of Information
Technology Equipment.
v Connect the equipment to a reliably grounded safety extra low voltage (SELV) source. An SELV
source is a secondary circuit that is designed so that normal and single fault conditions do not cause
the voltages to exceed a safe level (60 V direct current).
v Incorporate a readily available approved and rated disconnect device in the field wiring.
v See the specifications in the product documentation for the required circuit-breaker rating for
branch circuit overcurrent protection.
v Use copper wire conductors only. See the specifications in the product documentation for the
required wire size.
v See the specifications in the product documentation for the required torque values for the
wiring-terminal nuts.
The dc power supplies are customer replaceable units (CRUs) and do not require preventive maintenance.
Use only the supported dc power supplies for the storage subsystem.
Each dc 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), make sure that the environment is optimal (no overheating has occurred,
the dc power source is working, and so on). For more information, see "Restoring power after an
unexpected shutdown" on page 4-17.
If both dc 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 4-17.
Attention: The fans in the dc power supplies draw in fresh air and force out hot air. The dc 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 dc power supply, complete the following steps.
Chapter 5. Replacing components
5-27