Carrier OMNIZONE 50XJ064-104 Operating And Troubleshooting Manual

Also see for OMNIZONE 50BV020: Installation and service instructions

18Units not equipped with a water economizer can be orderedwith the reverse/head pressure control valve factory installedand a pressure transducer located in the discharge line ofcompressor no. 1.When the condenser water temperature gets low enough tocause the head pressure to drop, the valve will be modulated tocontrol the head pressure of all four compressors by varyingthe water flow through the condensers.When the unit is operating and the COOLOK softwarepoint is enabled and the EWT gets below 60 F, the Headsoftware point will become enabled and the head pressurecontrol valve will modulate to keep the head pressure at thehead pressure set point (SETPT04). The default set point is225 PSI and may be set from 200 to 250 PSI. The minimumoutput value for the head pressure control algorithm is 40% inorder to maintain a minimum flow through the condensers. Thevalve will modulate between 40 and 100%. Do not set theminimum lower than 40% or the compressors may shut downdue to low flow, resulting in the high-pressure switch tripping.VENTILATION REQUEST (50XJ) — The ventilation requestoutput will close a set of relay contacts to activate a ventilationdamper whenever the supply fan and supply fan status are bothtrue and the TIMECLOCK software point is on.VAV TERMINAL OPERATION OUTPUT (50XJ) — TheVAV terminal control output (TRMCT) closes a set of relaycontacts to indicate to non-Carrier air terminals that the fan iseither forced on or is going to turn on. This signals theterminals to open and start controlling to the desired CFM andTemperature set points.VAV TERMINAL OPEN OUTPUT (50XJ) — The VAV ter-minal open output (TRMOP) closes a set of relay contacts tocommand the air terminals to open to maximum CFM at timeswhen the fan is operating on the VFD Bypass.PUMP AND TOWER OUTPUTS (50XJ) — The pump andTower outputs close a set of relay contacts to indicate that the50XJ unit is in operation and may require condenser waterflow through the unit.BUILDING PRESSURE CONTROL (50XJ) — The buildingpressure control output provides an analog 4 to 20 mA signal tocontrol return fan or exhaust fan speed. Fan speed is modulatedto maintain the building static pressure set point (SETPT07).The control parameters for the building pressure set pointand building pressure are read and controlled in milliamps butare converted to inches of water for ease of setting and display.The range and low start values of the sensor selected should beconfigured in the custom configurations screen. The raw sensorvalue in milliamps will be displayed on the hardware pointBSP. The converted sensor reading in inches of H2O will bedisplayed at the software point BSP_IN. The set point input inSETPT07 in inches of H2O is converted to a raw milliamp setpoint in SETPT08. The algorithm controls to the milliampvalues since the math required for control using the staticpressure in inches generates numbers too small to be usedgiven the range of the controller configuration parameters.Diagnostic Features — The CC6400 provides a numberof features to help protect the unit and allow problemdiagnosis.CRITICAL FAULT — The controller provides an output(for field connection) to signal an external building systemsmonitor or control that the unit is not operating properly andhas shut down. A red light mounted on the front of the unitprovides visual indication of this alarm condition.NOTE: If the Local/Off/Remote switch is in the OFFposition, it is normal for the red alarm light on the displaypanel to be lit, indicating that the unit is disabled.NON-CRITICAL FAULT — The controller provides anoutput for a yellow light, mounted on the front of the unit, thatindicates the need for minor maintenance or service.FIRE INPUT (FSD) — This is a normally closed input, whichwhen opened, deenergizes an isolation relay in the unit, openingthe input to the controller. When this input turns On, all controloutputs are immediately turned Off, including the fan. Unitreset requires manual resetting at the main controller keypad.DUCT HIGH STATIC INPUT (DHS) — This air switchprovides backup protection for the ductwork. It is factoryinstalled in the unit, wired to the unit main controller to receive5 vdc. It is a normally open discreet switch, with adjustablemanual setting at the switch (range is 1 to 5 in. wg). Uponswitch closure, the controller immediately turns all outputs Off,including fan, and then indicates an alarm both by turning Onits Alarm Output, Red Alarm light and via communications.DIRTY FILTERS SWITCH (DFLTS) (50XJ) — This switchmeasures the change (delta) in air pressure across the filters.When the delta increases beyond the preset setting, a yellowwarning light will be lit, indicating that the filters need cleaningor replacement.The switch receives 5 vdc from the unit controller andmonitors air pressure delta across the return air filters. Switch isnormally open, with manually adjustable setting at the switchbetween 0.5 and 1.5 in. wg. Upon closure, controller shouldwait to assure closure for minimum 1 minute, then indicate analert via its non-critical alert output and via communications.All other unit operation should remain normal.COMPRESSOR OVERLOAD (COL)/SAFETIES — Eachcompressor circuit is provided with a temperature overloadboard (Copeland Protector Bd.), a Current Overload/SensorBoard (COL), High Pressure Switch (HPS), Low PressureSwitch (LPS), and Evaporator Freeze Switch (EFS). Thesedevices are wired in series to the contactor for each compressor.Each such circuit is then wired through a common resistor board;such that any one or more input(s) to the main controller allows itto discern which compressor is not operating when it should be.The Current Overload Board (COL) is located in the unitcontrol box, wired in the control power line for the compressorpilot relay (which drives the compressor contactor), andincorporates a current loop which monitors one leg of thecompressor power leads. This board is powered along with therelated compressor contactor.Whenever the compressor current falls below a thresholdlevel (i.e., compressor not operating), it activates an on-boardrelay which opens power to the compressor pilot relay (i.e.,compressor contactor), and turns On a control power feedbackline to the unit controller, via the resistor board (describedabove). Any one of the safety switches described herein willcause this event. In the event this occurs, the controller shallturn OFF this compressor, and start the next compressor insequence. After a 5-minute period, the controller shall restartthis compressor, and turn the other one off, as cooling demandrequires. If the ‘problem’ compressor then operates for 10 min-utes of run time normally, the unit reverts to normal operationand compressor sequencing. If not, and the same error occursagain, this compressor shall be shut down and replaced withthe next compressor, as before, and held off for 10 minutes. Itshall then be restarted and the other compressor shut down, asbefore. If it does not run successfully for 10 minutes of normalrun time again, it is shut down and replaced a third time. Thistime it is held off for 15 minutes. If the “problem” compressordoes not operate successfully for the 10 minutes of normal runtime this third time, this compressor ONLY is shut down andlocked out for servicing. Alarm output (Red light) flashes andthen remains on.HIGH-PRESSURE SWITCH (HPS) — This switch is locatedin the discharge refrigerant line of each compressor, and is setto open at pressures above 360 psig. It is wired in the 115 vaccontrol power line of the compressor contactor (in series withthe LPS and EFS), and activates the COL board (above) whenit opens.