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are appropriate for use in a typical outlet in the destination country. See
Appendix C, “Power cords,” on page 199 for more information.
Power and site wiring requirements for models with dc power
supply and fan units
The storage subsystem uses wide-ranging redundant power supplies that
automatically accommodate voltages to the dc power source. The dc power
supplies operate within the ranges specified in Table 21 on page 27. The dc power
supplies require a reliably grounded safety extra low voltage SELV source and an
approved and rated disconnect device for the -48V line.
The agency rating for the DS4700 Express Storage Subsystem (dc models) is 16
amps at -42V to -60V dc. This is the overall maximum operating current for the
DS4700 Express Storage Subsystem with dc power supply and fan unit CRUs.
DC power recovery: After a total dc power failure, after normal power is restored,
the storage subsystem performs power-up recovery procedures automatically
without operator intervention.
Power cords and receptacles: The storage subsystem ships with two dc power
jumper cables used to connect to the dc power source. See “Cabling the dc power
supply for dc models” on page 111 for more information.
Heat output, airflow, and cooling
See “Airflow and heat dissipation” on page 25 for heat output, airflow, and cooling
specifications.
Note: In general, disk subsystem reliability tends to decrease as the ambient
temperature of the environment in which it is being used increases. The
ambient temperature in the immediate area of the disk enclosure unit should
be kept near 22° C (72° F), or lower, to provide better reliability.
When racks that contain many storage subsystems are to be installed together, the
following requirements must be met to ensure that the storage subsystems are
adequately cooled:
v Air enters at the front of the rack and leaves at the back. To prevent the air that
is leaving the rack from entering the intake of another piece of equipment, you
must position the racks in alternate rows, back-to-back and front-to-front. This
arrangement is known as “cold aisle/hot aisle” and is shown in Figure 16 on page
29.
v Where racks are in rows, each rack must touch the rack that is next to it to
reduce the amount of hot air that can flow around from the back of the rack into
the intakes of the storage expansion enclosures that are in that rack. You should
use Suite Attach Kits to completely seal any gaps that remain between the racks.
For details about Suite Attach Kits, contact your marketing representative.
v Where racks are in rows front-to-front or back-to-back, a gap of at least 1220 mm
(48 in.) must separate the rows across the cold aisle.
v To ensure correct airflow in each rack, the rack filler plates must be installed in
unused positions. Also, all the gaps in the front of the racks must be sealed,
including the gaps between the storage subsystems.
28 IBM System Storage DS4700 Express Storage Subsystem: Installation, User’s and Maintenance Guide