Carrier 69NT20-531-300 manual Modes of Operation

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3.2.2 Operational Software (Function codes)

The Operational Software is the actual operation programming of the controller which activates or deactivates components in accordance with current unit operating conditions and operator selected modes of operation.

The programming is divided into function Codes. Some of the codes are read only while the remaining codes may be user configured. The value of the user configurable codes can be assigned in accordance with user desired mode of operation. A list of the function codes is provided in Table 3-5.

To access the function codes, perform the following:

a. Press the CODE SELECT key, then press an arrow key until the left window displays the desired code number.

b. The right window will display the value of this item for five seconds before returning to the normal dis- play mode.

c. If a longer time is desired, press the ENTER key to extend the time to 30 seconds.

3.3 MODES OF OPERATION

The Operational Software responds to various inputs. These inputs come from the temperature and pressure sensors, the temperature set point, the settings of the the configuration variables and the function code assignments. The action taken by the Operational Software will change if any one of the inputs changes. Overall interaction of the inputs is described as a “mode” of operation. The modes of operation include, perishable (chill) mode and frozen mode. Descriptions of the controller interaction and modes of operation are provided in the following sub paragraphs.

3.3.1 Temperature Control -- Perishable Mode

With configuration variable CnF26 (Heat Lockout Temperature) set to -10_C the perishable mode of operation is active with set points at or above -10_C (+14_F). With the variable set to -5_C, the perishable mode is active at or above -5_C (+23_F). Refer to Table 3-4.

When in the perishable mode the controller maintains the supply air temperature at set point, the SUPPLY indicator light will be illuminated on the display module and the default reading on the display window will be the supply temperature sensor reading.

When the supply air temperature enters the in-range temperature tolerance (as selected at function code Cd30), the in-range light will energize.

3.3.2 Defrost Interval

Function code Cd27 may be operator set to initiate defrost at intervals of 3, 6, 9, 12 or 24 hours. It may also be set to OFF (no defrost). The factory default is 12 hours. (Refer to Table 3-5).

3.3.3 Failure Action

Function code Cd29 may be operator set to allow continued operation in the event the control sensors are reading out of range. The factory default is full system shutdown. (Refer to Table 3-5).

3.3.4 Generator Protection

Function codes Cd31(Stagger Start, Offset Time) and Cd32 (Current Limit) may be operator set to control start up sequence of multiple units and operating current draw. The factory default allows on demand starting (no delay) of units and normal current draw. Refer to Table 3-5.

3.3.5Compressor High Temperature, Low Pres- sure Protection.

The controller monitors compressor suction and discharge temperatures and pressures. If the discharge temperature exceeds a certain limit, the liquid injection valve is opened to provide sufficient liquid refrigerant flow into the economizer line to reduce the discharge temperature. If the liquid injection is unable to reduce the discharge temperature sufficiently and the temperature exceeds the allowed limit, the compressor will cycle off on a 3 minute timer. The compressor will also cycle off in a similar manner if the suction pressure falls below the allowed limit. Condenser and evaporator fans continue to operate during the compressor off cycle.

3.3.6 Perishable Mode -- Conventional

The unit is capable of maintaining supply air temperature to within ¦0.25_C (¦0.5_F) of set point. Supply air temperature is controlled by positioning of the suction modulation valve (SMV), cycling of the compressor and cycling of the heaters.

When cooling from a temperature that is more than 2.5_C (4.5_F) above set point, the system will be in the perishable pull down mode. It will be in economized operation with a target SMV position of 100% open. However, pressure and current limit functions may restrict the valve, if either exceeds the preset value.

Once set point is reached, the unit will transition to the perishable steady state mode. This results in unloaded operation with some restriction of the SMV. The SMV will continue to close and restrict refrigerant flow until the capacity of the unit and the load are balanced.

If the SMV is at minimum modulation, the controller has determined that cooling is not required, or the controller logic determines suction pressure is at the low pressure limit, the unit will transition to the perishable idle mode. The compressor is turned off and the evaporator fans continue to run to circulate air throughout the container. If temperature rises above set point +0.2_C, the unit will transition back to the perishable steady state mode

If the temperature drops to 0.5_C (0.9_F) below set point, the unit will transition to the perishable heating

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Contents Service Model Safety Summary 309 Safety-2 Safety-3 309 Table of Contents Table of Contents Check Controller Function Codes Connect Remote MonitoringEvaporator Coil Replacement Evaporator Heater Replacement Valve ReplacementReplacing The Evaporator Fan Assembly Precheck Procedure Checking The Stepper valveElectrical Wiring Schematic Refrigeration Circuit Schematic Economized Operation Refrigeration Circuit Schematic Standard OperationList of Tables DataCORDER Configuration VariablesUnit is fitted with a scroll compressor Section IntroductionManual, T-300 Section Description Evaporator Section Compressor Section Condenser Section Communications interface module For further information Module which allow communication with a masterTemperature Model RSH105 Weight Dry 46.5 kg 103 lbApproved Oil Mobil ST32 Oil Charge 2957 ml 100 ounces Oil level range, with the compressor offElectrical Data Safety and Protective Devices Refrigeration Circuit 2.5.1 Standard Operation Standard Operation with Receiver Refrigeration Circuit Schematic -- Economized Operation Section Microprocessor Temperature Control SystemKEY Function Controller Software Modes of Operation Perishable Mode -- Economy Controller Alarms Unit PRE-TRIP Diagnostics DCF02=2 Thermistor inputssupply & returnDCF02=5 Usda thermistor inputs DCF02=6Raw Data Report for ABC1234567 Standard Configuration Download ReportLogging Interval dCF03 DataCORDER may be powered up in any one of four waysDataView DataCORDER Alarms Std, Full CnF11 Defrost Off Selection NoOFFCnF33 Snap Freeze Option SnAPDisplay Only Functions Possibly delaying a needed defrost cycle Defrost temperature sensor reading is displayedSensor Reading Plicable with frozen set pointsController Function Codes Sheet 3 Controller Alarm Indications Sheet 1 Controller Alarm Indications Sheet 2 Controller Alarm Indications Sheet 3 Memory failure Error DescriptionP1-1 Draw test is done after 15 secondsDraw test is done after 10 seconds OndsTest fails Supply is comparedP6-2 Crease, the test failsTimer is started Pressure switch is open or the condenser fan switch is openDenser fan is started and a 60 second timer is started Requirements Control temperature must be at least 15.6C 60FBy starting P10-0 over Requirements Control temperature must be at least 7.2C 45FSet point, the test proceeds to test Inapplicable Functions Display Title Data 10 DataCORDER Alarm Indications 69NT Fresh AIR Makeup OperationTo start a pre-trip test, do the following Will be displayedWill be displayed Pull Down Falling Rising Controller Operation -- Perishable ModeController Operation -- Frozen Mode Frozen Mode Defrost Section Troubleshooting Unit will not heat or has insuffi Bent motor shaft Will not initiate defrostSuperheat Unit reads abnormal currents Current sensor wiring Check Valve Frontseated Backseated Section ServiceCompressor in a deep vacuum, internal dam- age will result Refrigerant Leak Checking Remove all refrigerant using a refrigerant recovery system Refrigerant Charge Compressor Upper Mounting Compressor OIL Level Condenser FAN and Motor Assembly Removing the Expansion Valve Two expansion valves are used, the evaporatorWrapped with Insulating compound. See If applicable, braze the equalizer connection to Cleaned regularly. The preferred cleaning fluid is freshEqualizer line Check superheat refer to step14. Unloader Solenoid Valve Start unit and check operationEvaporator FAN Motor Capacitors Valve Override Controls Precheck Procedure TP1 Mounting Stud Type Cut one wire of existing cable 40 mm 1-1/2 inch Cut wires 5 cm 2 inches from shoulder of defecShorter than the other wire Cut one replacement sensor wire opposite colorMaintenance of Painted Surfaces 23 Door Hinge Repair Crack, Chip & Hole Repair Kit 24. Insert Location In-lbs Ft-lbs 13.99 18.86 In-lbs #10 Ft-lbs 12.72 17.1414.6 49.4 37.08 12.3 41.6 31.25 32.8 24.64 22.7 17.00 11.9 Section Electrical Wiring Schematic Schematic Diagram Wiring Diagram Sheet 1 Wiring Diagram Sheet 2 Index 309 Index-2

69NT20-531-300 specifications

The Carrier 69NT20-531-300 is a cutting-edge rooftop unit designed to meet the demanding requirements of commercial heating and cooling applications. This model embodies Carrier’s commitment to energy efficiency, reliability, and advanced technological features that enhance indoor comfort while minimizing operational costs.

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