Johnson Controls Frick 1179, Руководство пользователя, Страница: 48 / 64

RWH ROTARY SCREW COMPRESSOR UNITS
PROPER INSTALLATION OF ELECTRONIC EQUIPMENT
070.620-IOM (DEC 12)
Page 48
To install correctly, run a separate, properly sized (10 or 8
AWG typically) insulated ground along with and taken to
ground with, the 3­phase ground at the 3­phase supply
transformer (plant). This will require that the 3­phase ground
and the control power ground be electrically isolated except
for the connection at the plant supply transformer.
This style of grounding should steer the noise (EMI/RFI)
to earth ground, reducing the potential for it to affect the
sensitive equipment, which could occur if the grounds were
left coupled.
NOTICE
If all other recommendations for grounding are followed,
this process should not be necessary.
CONDUIT
All national and local codes must be followed for conduit
with regard to materials, spacing and grounding. In addition,
Johnson Controls-Frick requirements must be followed
where they exceed or match national or local codes. Con-
versely, there is no allowance for any practices that are
substandard to what is required by national or local codes.
Johnson Controls-Frick conduit requirements:
• For variable frequency drives (VFDs) of any type, threaded
metallic or threaded PVC­coated metallic is required
for both the power feed (line side) from the source and
between the VFD output and the motor (load side).
• PVC conduit is acceptable only when VFD rated cable
of the proper conductor size and ground is used. This
applies to both the line side and load side of the drive.
When VFD rated cable is not used, threaded metallic or
threaded PVC­coated metallic must be used.
• When threaded metallic or threaded PVC­coated metallic
is used, it must be grounded at both ends.
• When not required to be in metal or other material by
national or local codes, conduits for the power feed
(3­phase) of constant speed starters may be PVC.
• When not required to be in metal or other material by
national or local codes, conduits between a constant
speed starter and the motor (3­phase) may be PVC.
• Any unshielded control voltage, signal, analog, or com­
munication wiring that does not maintain 12 inches of
separation from any 3­phase conductors for every 33
feet (10 meters) of parallel run must be in metal conduit
which will be grounded.
Separation: (0­33 feet, 0­10 meters – 12 inches, .3 meters),
(33­66 feet, 10­20 meters – 24 inches, .6 meters)
• Since PVC conduit does absolutely nothing to protect
lower voltage lines from the magnetic field effects of
higher voltage conductors, running either the lower or
the higher voltage lines in PVC, does not reduce these
requirements on separation. Only running in metal conduit
can relieve these requirements.
• Due to the level of EMI that can be induced onto lower
voltage lines when running multiple feeders in a trench,
control power, communications, analog, or signal wiring
cannot be run in trenches that house multiple conduits/
electrical ducts carrying 3­phase power to starters/vfd
or motors.
• Control power, communications, analog, or signal wir­
ing should be run overhead (preferred) or in a separate
trench. If these lines are not in threaded metallic or
threaded PVC­coated metallic, abiding by the separation
requirements noted above is necessary.
• Though not recommended, if cable trays are used, metal-
lic dividers must be used for separation of conductors of
unlike voltages and types (AC or DC).
NOTICE
When in doubt contact the factory or use threaded
metallic or threaded PVC coated metallic conduit.
WIRING PRACTICES
Do not mix wires of different voltages in the same conduit.
An example of this would be the installation of a screw
compressor package where the motor voltage is 480 volts
and the electronic control panel power is 120 volts. The 480
volt circuit must be run from the motor starter to the motor
in its own conduit. The 120 volt circuit must be run from the
motor starter control transformer to the electronic control
panel in its own separate conduit. If the two circuits are run
in the same conduit, transients on the 480 volt circuit will be
induced onto the 120 volt circuit causing functional problems
with the electronic control panel. Metallic dividers must be
used in wire way systems (conduit trays) to separate unlike
voltages. The same rule applies for 120 volt wires and 220
volt wires. Also, never run low voltage wires for DC analog
devices or serial communications in the same conduit with
any AC wiring including 120 volt wires. See Figure 41.
Figure 41
Never run any wires through an electronic control panel
that do not relate to the function of the panel.
Electronic
control panels should never be used as a junction box. These
wires may be carrying large transients that will interfere with
the operation of the control panel.
An extreme example of
this would be to run 480 volts from the starter through
the electronic control panel to an oil pump motor.
When running conduit to the electronic control panel, use
the access holes (knockouts) provided by the manufacturer.