Johnson Controls Frick 1179, Руководство пользователя, Страница: 13 / 64

RWH ROTARY SCREW COMPRESSOR UNITS
INSTALLATION
070.620-IOM (DEC 12)
Page 13
are still operating and the HV2 valve on the suction bypass
is open.
For refrigeration plants using a Packaged Refrigerant Recir­
culation Unit and a direct expansion (DX) economizer system
it is necessary to operate the liquid feed solenoid on the unit
and the liquid feed solenoid on the DX vessel off of a common
signal to avoid liquid overfeed on the DX economizer system.
If multiple compressors are operated with a common
economizer vessel, it is necessary to install a back­pressure
regulator valve with an electric shutoff option in the vapor
line piped to the compressor's economizer port.
ECONOMIZER LOAD BALANCING
The most energy efficient manner to operate an economizer
system, when using multiple compressors on a common
economizer vessel, is to take as much of the flash gas as
possible to the compressors that are fully loaded. This can
be done in at least two ways.
1. Use the economizer output from the microprocessor to
turn off a solenoid, or to actuate the electric shutoff option
on a back­pressure regulator, based on percent of slide valve
travel. This will direct all the flash vapor to the other loaded
compressors.
2. A dual­setpoint, back­pressure regulator valve can be
used in each of the individual economizer vapor lines. When
a compressor is running near full load, the BPR valve will
operate on the desired setpoint, or basically wide open, to
minimize pressure drop in the line. When one compressor
unloads below the slide valve position where the economizer
output on the microprocessor turns on, the dual­setpoint
feature of the regulator can be actuated by this output to
control the pressure, on the vessel side of the regulator, to
be a few psi higher. Consequently, the flash gas will be sent
to the loaded compressors first, until they can’t handle all
the vapor and the pressure in the vessel starts to rise. Then,
some of the vapor will go to the unloaded compressor to
help maintain the vessel at the desired pressure. An example
of a back­pressure regulator with electric shutoff and the
dual­setpoint feature is an R/S A4ADS.
ELECTRICAL
NOTICE
Before proceeding with electrical installation, read the
instructions in the section “Proper Installation of Elec-
tronic Equip ment in an Industrial Environment.”
RWH units are supplied with a Quantum™LX control system.
Care must be taken that the controls are not exposed to
physical damage during handling, storage, and installa tion.
The single­box control door must be kept tightly closed to
prevent moisture and foreign mat ter from entry.
NOTICE
All customer connections are made in the single-box
control mounted on the oil separator. This is the ONLY
electrical enclosure and it should be kept tightly closed
whenever work is not being done in it.
VOLTAGE PROTECTION
Frick
®
does not advise nor support the use of UPS power
systems in front of the Quantum
™
LX panel. With a UPS power
system providing shutdown protection for the Quantum
™
LX,
the panel may not see the loss of the 3­phase voltage on
the motor because the UPS could prevent the motor starter
contactor from dropping out. With the starter contactor still
energized, the compressor auxiliary will continue to feed
an “Okay” signal to the panel. This will allow the motor to
be subjected to a fault condition on the 3­phase bus. Some
fault scenarios are:
1. The 3­phase bus has power “on” and “off” in a continu­
ous cyclic manner which may cause the motor to overheat
due to repeated excessive in­rush currents.
2. Motor cycling may damage the coupling or cause other
mechanical damage due to the repeated high torque motor
“bumps”.
3. Prolonged low voltage may cause the motor to stall and
overheat before the motor contactor is manually turned off.
Under normal conditions, the loss of 3­phase power will shut
down the Quantum
™
LX panel and it will restart upon power
return. If the panel was in:
• Auto – Compressor motor will return to running as pro­
grammed.
• Remote – The external controller would reinitialize the
panel and proceed to run as required.
• Manual – The compressor will have to be restarted
manually after the 3­phase bus fault has been cleared.
If the local power distribution system is unstable or prone
to problems, there are other recommendations to satisfy
these problems. If power spikes or low or high line voltages
are the problem, then we recommend the use of a Sola ®
constant voltage (CV) transformer with a line suppression
feature. If a phase loss occurs, then you will typically get a
high motor amp shutdown. If problems continue to exist, then
an examination of the plant’s power factor may be in order.
Unless careful design failure analysis is considered in the
implementation of power systems, the alternative solutions
provide a safer and less expensive implementation. In either
case, only one Sola ® may be used per compressor. Each
compressor needs to be individually isolated from each other
through a dedicated control transformer. Sharing a common
control power source is an invitation for ground loops and
the subsequent unexplainable problems.
MOTOR STARTER PACKAGE
Motor starter and interlock wiring require ments are shown in
the Starter Wiring Diagram . All of the equipment shown is
supplied by the installer unless a starter package is pur chased
separately from Johnson Controls­Frick. Starter packages
should consist of:
1. The compressor motor starter of the specified HP and
voltage for the starting method specified (across­the­line,
wye­delta, or solid­state).