Unit installation

PROSTAR DCS COMPACT INSTALLATION
TECHNICAL MANUAL PART 2 JUNE 1995
2–3
supplementary equipment grounding conductor shall be in compliance with the rules
for terminating bonding jumpers in Part K of Article 250 of the National Electrical Code
ANSI/NFPA 70. Termination of the supplementary equipment grounding conductor is
permitted to be made to building steel, to a metal electrical raceway system, or to any
grounded item that is permanently and reliably connected to the electrical service
equipment ground.
“66.2.C Bare, covered, or insulated grounding conductors are acceptable. A covered or
insulated grounding conductor shall have a continuous outer finish that is either green,
or green with one or more yellow stripes.
“Paragraph 66.2 revised September 20, 1993.”
Failure to provide an adequate ground may cause a safety hazard, confusing trouble
symptoms or even circuit card failure.
WARNING: Unplug the power cord from the AC outlet before attempting to connect
the ground. Hazardous voltage may cause death or injury. Observe extreme caution
when working with AC power.
What the above paragraphs mean is when conventional, analog telephone circuits are
connected to the DCS COMPACT system, under fault conditions (e.g., the tip and/or
ring conductor is crossed with a power line, the circuit is affected by lightning during a
storm), it is possible for hazardous potentials to appear across the tip and ring wiring
coming into the DCS COMPACT cabinet from the outside plant (e.g., overhead cables,
buried cables, cable head pedestal). These circuits are provided with both primary and
secondary protection circuitry which will attempt to drain off these high voltages and
currents to earth ground. Obviously, it is important to have a good source of ground
connected to the DCS COMPACT system to which to drain this energy off. Also, certain
metallic analog circuits (e.g., E & M trunks) require a current flow to earth ground to
accommodate normal operating conditions and/or to resolve fault conditions. Again, a
good earth ground source is required by the DCS COMPACT system.
The DCS COMPACT system is grounded in two ways. One way is via the green wire in
the power cord connected to the AC power outlet. However, this can be disconnected
either intentionally or unintentionally. Consequently, a second or supplementary more
permanent ground connection is provided by connecting a high current/voltage
capacity ground wire which is bonded to ground at the electric service power entrance
or via some other method approved by the National Electrical Code to the DCS
COMPACT system ground lug. This is a more secure ground connection which can
only be disconnected intentionally. These precautions are basically taken for safety
reasons to protect personnel working on the DCS COMPACT system and also for
operational reasons to accommodate ground return and/or ground referenced analog
telephone circuits which require this solid earth ground connection for normal
functioning.
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