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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 The branch circuit overcurrent protection must be rated 20 A.
v Use 12 American Wire Gauge (AWG) or 2.5 mm2 copper conductor only, not
exceeding 4.5 meters in length.
v Incorporate a readily available approved and rated disconnect device in the
field wiring.
CAUTION:
Disconnect the dc power jumper cord from the dc connector on the dc power
supply and fan unit before replacing the dc power supply and fan unit.
The dc power supply and fan unit is a component that includes both a -48 V power
supply unit and two fans. The dc power supplies provide power and cooling for the
DS4700 Express. The dc power supplies are customer replaceable units (CRUs)
and do not require preventive maintenance. Use only the supported dc power
supplies for your specific storage subsystem.
Each dc 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 137.
The storage subsystem cooling system consists of two fans in each of the two dc
power supply and fan unit CRUs. The dc power supplies circulate air from the front
to the back of the unit.
If both dc power supplies fail, or if the dc power supplies cannot maintain an
internal temperature below 68° C (154° F), the dc power supplies in the unit 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 137.
170 IBM System Storage DS4700 Express Storage Subsystem: Installation, User’s and Maintenance Guide