Carrier Infinity 24VNA6 Series Service Manual

Also see for Infinity 24VNA6: Installation instructions Owner's manual

24VNA6 / 25VNA4: Service ManualManufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.5Variable Frequency Drive (VFD)The VFD converts single phase 60 Hz line power into a variablefrequency, variable voltage, 3-phase output to drive the compressor atthe speed requested by the control system. This function is performedby first converting the incoming line power to an intermediate highvoltage DC supply. The high voltage DC supply is then converted to a3-phase output by a variable frequency inverter for driving thecompressor. The VFD also provides high voltage DC supply power tothe fan motor.The VFD contains numerous protection modes for maximizingreliability and preventing faults in wiring or the compressor and fancomponents from causing failures within the VFD.VFD Filter BoardThe VFD filter board blocks electrical noise generated within the VFDfrom back-feeding onto the line power feed to the equipment. It containsnon-replaceable fuses which will protect the VFD in the event of asevere power surge condition.ReactorsReactors are part of the VFD incoming power conversion circuit. Thereactors enable boosting of incoming line power when necessary andalso provide power factor correction.High Pressure Switch (HPS)The HPS is a normally closed switch connected to VFD control circuitry.The HPS opens when the compressor discharge pressure reaches 670psig. When the switch opens, a control input to the VFD is disabled andcauses the compressor and fan to shut down. When compressordischarge pressure decreases to 470 psig, the switch closes and allowsequipment operation to resume.Compressor Brushless Permanent Magnet Motor(BPM)The compressor uses a highly efficient, brushless permanent magnetmotor. Motor speed is synchronized to, and controlled by the frequencyof the drive provided by the VFD.VFD + Compressor BPMCompressor runs at variable speeds controlled by the VFD.The VFD controls acceleration and deceleration speeds of thecompressor. Speed changes are typically limited to 60 rpm per second.The VFD will automatically limit compressor speed if compressor loadcurrent reaches operating limits.Fan Brushless Permanent Magnet Motor (BPM)The fan uses a highly efficient, brushless permanent magnet motor.Motor speed is synchronized to, and controlled by an on-board variablefrequency inverter (VFI) integrated with the motor and located withinthe motor housing. The VFI uses the high voltage DC supply providedby the VFD to drive the fan, and a low voltage control signal from theVFD to determine fan speed. The fan provides a feedback signal to theVFD indicating fan speed.VFD + Fan BPMThe fan runs at a variable speed over a range of 200 rpm to 800 rpmdepending on air movement requirements.The fan on-board VFI will automatically limit fan speed if fan loadcurrent reaches operating limits.Crankcase HeaterSome equipment has a crankcase heater band installed around thecompressor case near the bottom of the compressor. The heater isenergized when the outdoor ambient temperature drops below 65°F andis de-energized when the outdoor ambient temperature goes above 85°F.Heating the compressor prevents liquid refrigerant from accumulating inthe compressor by ensuring that the compressor is not the coldest part ofthe system. The crankcase heater operates independently of indoorequipment and System Control and functions as needed any time theoutdoor equipment is powered.Some equipment has an internal stator heating function without acrankcase heater. The compressor windings will occasionally beenergized during the OFF cycle to start the stator heat operation, thusmaintaining a sump temperature that is essential for compressorreliability. The compressor will not run during this process. Theequipment that utilizes the stator heating function does not include acrankcase heater, have PCM SW version 5.0 or higher, and utilizes newVFD hardware and software. The VFD part numbers HR46VP002,HR46VQ002, and HR46VR002 include the stator heating function.With either crankcase heating or stator heating the system must bepowered on for a minimum of 24 hours prior to starting the system toensure that liquid refrigerant is not present in the compressor.CONTROL SUB-SYSTEMThe control sub-system provides the connection point for low voltagefield communication and control wiring. The control sub-systemcontrols all operation of the equipment.Primary Control Module (PCM)The PCM is the heart of the equipment control system. The PCM is theconnection point for all control components except for the high pressureswitch and crankcase heater (when present).The PCM receives equipment control requests from a communicatingInfinity Control or from a non-communicating control (traditionalthermostat) in an emergency operating mode.The PCM receives signals from numerous sensors, including:• 4 thermistors: OAT, OCT, OST, PDT• 2 pressure transducers: SPT, DPT.The PCM controls numerous actuators and signals, including:• 3 control solenoids: PEV, RVS and LLS• 2 electronic expansion valves: EXV-H, EXV-VI• VFD Control Interface• Emergency Mode 24VAC Control Signals: O and WThe PCM performs numerous diagnostics and supports 120 diagnosticcodes. Each of these codes is described in the Troubleshooting section.Diagnostics cover the following:• Line voltage and communication• Equipment configuration (model plug, etc.)• Compressor and fan operation• Sensors• ActuatorsThe PCM contains indicators and displays to provide operating statusand conditions. The PCM also supports communication with the CarrierService Tech App through the Bluetooth Module which providesdetailed diagnostic information and reprogramming capability.