Comdial DXP Plus Series, Руководство пользователя

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2.0 Understanding System Grounding Requirements
Transient voltage spikes, if induced onto CO or CENTREX lines, can travel through the cable and into the
common equipment. The telephone company offers basic protection against this condition but it is usually
designed to protect the central office circuits. While it will also provide some protection to the common
equipment, you should not rely upon it for total protection. To help ensure that external over-voltage surges do not
damage the system, you should install and properly ground primary protection devices, such as gas discharge
tubes or similar primary protection devices, on all lines. While the line boards have internal secondary surge
protection on all line ports, in order for this protection to be effective, you MUST connect the common equipment
cabinet to a reliable, effective earth ground.
Proper grounding is necessary for trouble-free operation and personnel safety. The DXP Plus has the following
three types of grounds:
•
Service Ground —a neutral power line wire that is connected to the ground bus in the premises’ AC power
panel,
•
System Ground—a non-current carrying power line wire that is connected to the ground bus in the premises’
AC power panel,
•
Frame Ground—a low impedence conductor that places the common equipment cabinet at reference ground
potential. The frame ground provides the greatest safety by limiting electrical potential between non-current
carrying parts of the system. The common equipment cabinet provides a ground stud on its cabinet for access to
its frame ground.
The entire system is effectively earth-grounded when you permanently connect the common equipment cabinet,
all expansion cabinets, and the battery back-up assembly to earth or to some conducting body which serves in
place of earth. The ground path must be of sufficient current-carrying capacity to prevent a build up of voltages
which may result in circuit noise, hazard to personnel, or equipment damage.
An acceptable earth ground is one such as the service ground for the AC power or a public metallic cold water
pipe at a point immediately at its entrance to the premises and ahead of any meters, pumps, or insulating sections
that have been added for vibration reduction. Avoid using the premises’ structural steel frame as it may not be at
earth ground potential. Use #10–12 or larger insulated solid copper grounding wire to connect the frame ground of
the battery assembly cabinet (available through the ground stud on the cabinet’s side) to the frame ground of the
main common equipment cabinet. Use #6 or larger insulated solid copper grounding wire to make the ground
connection from the main cabinet’s frame ground to earth ground. Keep this ground wire separate from the
three-wire AC line cord, do not splice it, and keep it as short as possible.
The impedence of the wiring between the common equipment cabinet frame ground and the earth ground must not
exceed 0.25 ohms and the impedence between the earth ground and the power company’s reference standard
ground must not exceed 5 ohms. Use an acceptable low impedence measuring device to measure the impedence of
these paths. The #6 or larger wire size will minimize the wiring impedence; however, if the impedence between
earth ground and the power company’s standard reference ground exceeds 5 ohms, contact the local power
company. The ground path must always be of sufficient current-carrying capacity to prevent a build up of voltages
that may result in circuit noise, hazard to personnel, or equipment damage.
Be sure that all of the ground connections are visible for inspection and maintenance. Tag all of the ground
connections with a sign that reads: Do Not Remove or Disconnect.
IMI89–197 Installing The Switchable Battery Back Up Assembly
2 – Installing The Battery Back Up Assembly