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Unitsnot equippe d witha w ater economizer can be ordered
with the reverse/head pressure control valve factory installed
and a pressure transducer located in the discharge line of
compressorno. 1.
When the condenser water temperature gets low enough to
causethe hea d pressure to drop, the valve will be modulated to
control the head pressure of all four compressors by varying
thewater flow throughthe condensers.
When the unit is operating and the COOLOK software
point is enabled and the EWT gets below 60 F, the Head
software point will become enabled and the head pressure
control valve will modulate to keep the head pressure at the
head pressure set point (SETPT04). The default set point is
225 PSI and may be set from 200 to 250 PSI. The minimum
output value for the head pressure control algorithm is 40% in
orderto maintain a minimum flow through the condensers. The
valve will modulate between 40 and 100%. Do not set the
minimum lower than 40% or the compressors may shut down
dueto low flow, resulting in the high-pressure switch tripping.
VENTILATIONREQUEST (50XJ) — The ventilation request
outputwill close a set of rel ayc ontacts to activate a ventilation
damperwhenever thesupply fan andsupply fan status a re both
trueand the TIM ECLOCK software point is on.
VAV TERMINALOPERATION OUTPUT (50XJ) — The
VAV terminal control output (TRMCT) closes a set of relay
contacts to indicate to non-Carrier air terminals that the fan is
either forced on or is going to turn on. This signals the
terminals to open and start controlling to thede sired CFM and
Temperatureset points.
VAV TERMINAL OPEN OUTPUT (50XJ) — TheVAVter-
minal open output (TRMOP) closes a set of relay contacts to
command the air terminals to open to maximum CFM at times
whenthe fan is operat ingon t heV FD Bypass.
PUMP AND TOWER OUTP UTS (50XJ) — The pump and
Toweroutputs close a set of rel ay contacts to indicate that the
50XJ unit is in operation and may require condenser water
flowthrough the unit.
BUILDINGPRESSURE CONTROL (50XJ) — The building
pressurecontrol output provides an analog 4 to 20 mA signal to
controlreturn fan or exhaust fan speed. Fan speed is modulated
tomaintain the building static pressure set point (SETPT07).
The control parameters for the building pressure set point
and building pressure are read and controlled in milliamps but
areconvert ed to inches of water for ease of setting and display.
Therange and low start values of the sensor selected should be
configuredin the custom configurations scre en. The raw sensor
value in milliamps will be displayed on the hardware point
BSP.The c onverted sensor reading in inches of H2Owillbe
displayed at the softwarepoint BSP_IN. The set point input in
SETPT07in inches of H 2O is converted to a raw milliamp set
point in SETPT08. The algorithm controls to the milliamp
values since the math required for control using the static
pressure in inches generates numbers too small to be used
giventhe range of the controller configurat ion parameters.
DiagnosticFeatures — The CC6400 provides a number
of features to help protect the unit and allow problem
diagnosis.
CRITICAL FAULT — The controller provides an output
(for field connection) to signal an external building systems
monitor or control that the unit is not operating properly and
has shut down. A red light mounted on the front of the unit
providesvisual indicat ion of this alarm condition.
NOTE: If the Local/Off/Remote switch is in the OFF
position, it is normal for the red alarm light on the display
panelto be lit, indicating that the unit is disabled.
NON-CRITICALFAULT — The controller provides an
output fora yellow light, mounted on the front of the unit, that
indicatesthe nee d for minor maintenance or service.
FIRE INPUT ( FSD) — This is a normally closed input, which
whenopened, deenergizes an isolation relay in the unit, opening
theinput to the controller. When this input turns On, all control
outputs are immediately turned Off, including the fan. Unit
resetrequires manual resetting at the main controller keypad.
DUCTH IGH STATICINPUT (DHS) — This air switch
provides backup protection for the ductwork. It is factory
installedin the unit, wi red to the unit main controller to receive
5 vdc. It is a normally open discreet switch, with adjustable
manual setting at the switch (range is 1 to 5 in. wg). Upon
switchclosure, the controller immediately turns al loutputs Off,
including fan, and then indicates an alarm both by turning On
itsAlarm Output, Red A larm light and via communications.
DIRTYFILTERSSWITCH(DFLTS)(50XJ)—Thisswitch
measures the change (delta)in air pressure across the filters.
When the delta increases beyond the preset setting, a yellow
warninglight will be lit, indi cating that the filters need cleaning
orreplacement .
The switch receives 5 vdc from the unit controller and
monitorsair pres sure delta across the return air filters. Switch is
normally open, with manually adjustable setting at the switch
between 0.5 and 1.5 in. wg. Upon closure, controller should
wait to assure closure for minimum 1 minute, then indicate an
alert via its non-critical alert output and via communications.
Allother unit operat ionshould remainnormal.
COMPRESSOR OVERLOAD (COL)/SAFETIES— Each
compressor circuit is provided with a temperature overload
board (Copeland Protector Bd.), a Current Overload/Sensor
Board (COL), High Pressure Switch (HPS), Low Pressure
Switch (LPS), and Evaporator Freeze Switch (EFS). These
devicesare wired in series to the contactor for each compressor.
Eachsuch circuit is then wire d through a common resistor board;
suchthat any one or more input(s) to the main control ler allows it
todiscern whi ch compressor is not operating when it should be.
The Current Overload Board (COL) is located in the unit
controlbox, wired inthe controlpow er line for the compressor
pilot relay (which drives the compressor contactor), and
incorporates a current loop which monitors one leg of the
compressor powerl eads. Thisboard i spowered along w iththe
relatedcompressor contactor.
Whenever the compressor current falls below a threshold
level (i.e., compressor not operating), it activates an on-board
relay which opens power to the compressor pilot relay (i.e.,
compressor contactor), and turns On a control power feedback
line to the unit controller, via the resistor board (described
above). Any one of the safety switches described herein will
cause this event. In the event this occurs, the controller shall
turn OFF this compressor, and start the next compressor in
sequence. After a 5-minute period, the controller shall restart
this compressor,and turn the other one off, as cooling demand
requires.If the ‘problem’ compressor then operates for 10 min-
utes of run time normally,the unit reverts to normal ope ration
and compressor sequencing. If not, and the same error occurs
again, this compressor shall be shut down and replaced with
the next compressor, as before, and held off for 10minute s.It
shall then be restarted and the other compressor shut down, as
before.If it does not run successfully for 10 minutes of normal
run time again, it is shut down and replaced a third time. This
time it is held offfor 15 minutes. If the “problem” compressor
does not operate successfully for the 10 minutes of normal run
time this third time, this compressor ONLY is shut down and
locked out for servicing. Alarm output (Red light) flashes and
then remains on.
HIGH-PRESSURE SWITCH (HPS) — This switch is located
in the discharge refrigerant line of each compressor, and is set
to open at pressures above 360 psig. It is wired in the 115 vac
control power line of the compressor contactor (in series with
the LPS and EFS), and activates the COL board (above) when
itopens.