Carrier 48LC Series Controls, Start-up, Operation And Troubleshooting

Also see for 48LC 05: Controls, Start-Up, Operation and Troubleshooting Service and maintenance instructions Service and maintenance instructions

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Carrier 48LC Series Controls, Start-up, Operation And Troubleshooting Manual pdf 22 page image

22HUMIDI-MIZER COILCOMPRESSOROUTDOOR AIRINDOOR SUPPLYAIRINDOOR RETURNAIR3-WAYVALVERDVVALVEEVAPORATOR COILCONDENSER COIL= CLOSED VALVE= OPEN VALVE= 3-WAY VALVEEXPANSIONVALVE(TXV)C14116Fig. 18 -- Hot Gas Reheat Mode – Humidi--MiZer System 48/50LC 07--26Reheat Mode Diagnostic HelpThe status of reheat mode sensor inputs may be viewed within thedisplay INPUTS menu. The status of reheat mode outputs may beviewed within the display OUTPUTS or RUN STATUSMODEmenu. Additional diagnostic help, including status of circuit reheattemperature limit lockouts may be viewed within theHumidi--MiZer sub--menu of the cooling mode diagnostic table atRUN STATUSCOOLDEHUM. The Service Test mode maybe used to force the system to operate Dehumidification mode (HotGas Reheat) and Dehum/Mech Cooling mode (Subcooling), or toindependently operate the reheat valve control outputs.The following forced operating states are available service testoperations for a Humidi--MiZer system equipped unit:SERVICE TEST  COOL TEST  HUMIDIMIZER TESTLEVELA value of “0” sets reheat control test to “Off.”SERVICE TEST  COOL TEST  HUMIDIMIZER TESTLEVELA value of “1” sets Humidi--MiZer control test to “Dehum/MechCooling mode (Subcooling).”SERVICE TEST  COOL TEST  HUMIDIMIZER TESTLEVELA value of “2” sets Humidi--MiZer test to “Dehumidification mode(Hot Gas Reheat).”SERVICE TEST  INDEPENDENTS  LIQ DIVERT A TESTA value of “On” will turn on the 3--Way Liquid Diverter Valve(LDV).SERVICE TEST  INDEPENDENTS  REHEAT A TESTA value of “On” will turn on the Reheat Discharge Valve (RDV).Indoor Fan Based DehumidificationBelt Drive units that are not factory configured for Humidi--Mizeroperation can be set for improved dehumidification operationthrough fan based humidification (FBD), SETTINGS UNITCONFIGURATIONS COOLING FBD TYPE. Units arefactory defaulted to FBD TYPE = 0 which means that any dehumdemand is ignored. There are two fan based dehumidificationoptions, Max Comfort (FBD TYPE = 1) and MaxDehumidification (FBD TYPE = 2). Fan based dehumidificationrequires the installation and configuration of either a space relativehumidity sensor or a relative humidity switch input. The SpaceHumidity Switch configuration, SETTINGS UNITCONFIGURATIONS SWITCH INPUTS CONFIGSHUMSTAT CHANNEL identifies the normally open or normallyclosed status of this input at HIGH humidity. The RH Sensorconfiguration, SETTINGS UNIT CONFIGURATIONSANALOG INPUTS CONFIGS SPRH SENSOR CHANNEL,identifies the point on the MBB (Main Base board) or the IOB(Input Output board) the sensor was wired into.Max DehumWhen the FBD Type is set to (2) Max Dehum, the control will try tosatisfy the dehumidification demand. When the unit receives a dehumdemand a PID control algorithm will modulate the indoor fan whilethe compressor is running to maintain minimum suction temperature(FBDH_SST). With a Y1 and dehum demand, the unit will run thecompressor unloaded (48/50LC04--06) or will run the A1 compressoronly (48/50LC07--26). With a Y2 and dehum demand, the unit willrun with the compressor at full load (48/50LC04--06) or will run withthe A2 compressor only (48/50LC07--26). With a Y3 and dehumdemand (48/50LC07--26 only), the unit will run both compressors.Max ComfortWhen the FBD Type is set to (1) Max Comfort, the control will tryto satisfy the dehumidification demand and minimize cold airdump. When the unit receives a dehum demand a PID controlalgorithm will modulate the indoor fan while the compressor isrunning to maintain the minimum FBD supply air comfort setpoint (FBDH_SAT) while also maintaining the minimum suctiontemperature (FBDH_SST). With a Y1 and dehum demand, the unitwill run the compressor unloaded (48/50LC04--06) or will run theA1 compressor only (48/50LC07--26). With a Y2 and dehumdemand, the unit will run with the compressor at full load(48/50LC04--06) or will run with the A2 compressor only(48/50LC07--26). With a Y3 and dehum demand (48/50LC07--26only), the unit will run both compressors.Heating OperationThe 48/50LC unit’s heating operation consists of: demand andmode determination, staging request to satisfy the demand, andhandling a request with the unit’s resources. These resources can begas heat or electric heat. This section covers both gas heat units andelectric heat units. The Type of Heat Installed (UNIT TYPE OFHEAT) configuration will be factory set to 1 for gas units and 0 forelectric heat units. The unit enters a heating mode based on ademand, decides how to satisfy the demand, executes its plan, andthen leaves the heating mode.Heating Mode ControlThe heating HVAC mode (OPERATING MODE) has 3 differentoperating sub modes (SUBMODE): HEATING, HEATINGPREVENTED, and SHUTTING HEAT OFF. These are all part ofa general heating mode and resemble the action heat mode is taking