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Electrical Power
(Continued)
Grounding
A machine 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. For some small machines such as
terminals, a continuous metallic conduit is adequate for
grounding.
To ensure proper grounding, a licensed electrician should
check the grounding and receptacles for conformance with
the country electrical codes.
For personnel safety, the ground must have sufficiently
low impedance to limit the voltage to ground and to
operate the circuit protective devices if a phase-to-frame
short occurs. For example, the ground path shall not
exceed 1 ohm for 120-volt, 20-ampere branch circuit
devices.
Computer Room Emergency Power-Off Controls
As a safety precaution, 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.
Follow national and local electrical codes.
Lightning Protection
1-10
You should install lightning protection devices when:
•
An over!J.ead power service supplies the primary power
•
The utility company installs lightning protectors on
the primary power source
•
The area is subject to electrical storms or
equivalent-type power surges.
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