Notes:
1. Feature codes 6173, 6174, 9173 , 9174, 7178 and 9178 are for a rack-mounted power distribution and
include a power cord and plug that attaches to the power distribution unit (PDU). It is not necessary to
order a line cord when one of these feature codes is selected.
Single phase PDUs 6171, 9171 7176, 9176, 7177, and 9177 must have a power cord specified.
2. In the United States, raised floor installations involving racks may require a Russell and Stoll (R & S)
watertight plug/connector/receptacle (feature code 9801 or 9987).
3. A combination of ac PDUs and dc power distribution panels (PDPs) in one rack will only be provided
on a special-order basis.
System Input Power
Most of the following input power considerations apply to all system units, except for the ″Power Phase
Imbalance″ and ″Power Phase Rotation″ sections, which apply only to the rack-mounted or large systems.
Electrical Considerations
These topics should be considered before you install a system.
Primary Computer Power Service
While a dedicated power supply is not necessary, for maximum reliability, the computer power panel
should connect to feeders that do not serve other loads. Connect electrical noise-producing devices to
panels separate from those feeding the system units.
Grounding
A system unit or device must be properly grounded. It is recommended that an insulated green wire
ground, the same size as the phase wire, be installed between the branch circuit panel and the receptacle.
To ensure proper grounding, a licensed electrician should check the grounding and receptacles for
conformance with the country electrical codes.
Computer Room Emergency Power-Off Controls
As a safety precaution, you should provide room emergency power-off controls for disconnecting the main
service wiring that supplies the computer equipment. Install these controls at a convenient place for the
operator and next to the main exit doors of the room.
Lightning Protection
You should install lightning protection devices when:
v An overhead power service supplies the primary power.
v The area is subject to electrical storms or equivalent-type power surges.
Power Phase Imbalance
Three versions of rack power distribution units are available. The single-phase PDU, has a detachable line
cord and can accept single-phase power or power from one phase of a three-phase source. Multiphase
PDUs connect to two and three phases of a three-phase power source.
Systems with any of the power distribution units can cause a load imbalance when connected to a
three-phase power source. You should consult a licensed electrician to properly balance the loads when
new or additional systems are to be connected to a three-phase source.
Power Phase Rotation
The phase rotation (sequence) is not critical for the rack multiphase power distribution units. The system
will operate correctly with a multiphase distribution unit connected to a 200- to 240-volt single-phase power
source (all phases connected to one side of the power source, neutral to the other).
338 Site and Hardware Planning Information
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