Midea M thermal Mono Series Service Manual
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Midea M thermal Mono Series Service Manual

Commercial air conditioners
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R32
Commercial Air Conditioners
Service
Manual
M thermal Mono Series
Midea CAC Confidential

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Summary of Contents for Midea M thermal Mono Series

  • Page 1 Commercial Air Conditioners Service Manual M thermal Mono Series Midea CAC Confidential...
  • Page 2 M thermal Mono CONTENTS Part 1 General Information ................3 Part 2 Component Layout and Refrigerant Circuits ........5 Part 3 Control ....................15 Part 4 Diagnosis and Troubleshooting ............31 202004 Midea CAC Confidential...
  • Page 3 M thermal Mono 202004 Midea CAC Confidential...
  • Page 4 M thermal Mono 202004 Midea CAC Confidential...
  • Page 5 M thermal Mono Part 1 General Information 1 Unit Capacities and External Appearance ..........4 202004 Midea CAC Confidential...
  • Page 6 For example, the model name for the 8kW model is MHC-V8W/D2N8. The presence or omission of the letter R in the model names indicates the unit’s power supply:  R: 3-phase, 380-415V, 50Hz; Omitted: 1-phase, 220-240V, 50Hz. 1.2 External Appearance Table 1-1.2: Unit appearance 4/6kW 8/10/12/14/16kW 202004 Midea CAC Confidential...
  • Page 7 M thermal Mono Part 2 Component Layout and Refrigerant Circuits 1 Layout of Functional Components .............. 6 2 Piping Diagrams ..................11 3 Refrigerant Flow Diagrams ............... 13 202004 Midea CAC Confidential...
  • Page 8 M thermal Mono 1 Layout of Functional Components MHC-V4W/D2N8-B / MHC-V6W/D2N8-B Figure 2-1.1: MHC-V4(6)W/D2N8-B top view Figure 2-1.2: MHC-V4(6)W/D2N8-B front view 202004 Midea CAC Confidential...
  • Page 9 M thermal Mono Figure 2-1.3: MHC-V4(6)W/D2N8-B 202004 Midea CAC Confidential...
  • Page 10 M thermal Mono MHC-V8W/D2N8-B / MHC-V10W/D2N8-B Figure 2-1.1: MHC-V8(10)W/D2N8-B top view Figure 2-1.2: MHC-V8(10)W/D2N8-B front view 202004 Midea CAC Confidential...
  • Page 11 M thermal Mono MHC-V12W/D2N8-B / MHC-V14W/D2N8-B / MHC-V16W/D2N8-B Figure 2-1.4: MHC-V12(14, 16)W/D2N8-B top view Figure 2-1.5: MHC-V12( 14, 16)W/D2N8-B, MHC-V12(14, 16)W/D2RN8-B front view MHC-V12W/D2RN8-B / MHC-V14W/D2RN8-B / MHC-V16W/D2RN8-B 202004 Midea CAC Confidential...
  • Page 12 M thermal Mono Figure 2-1.4: MHC-V12(14, 16)W/D2RN8-B top view Figure 2-1.5: MHC-V12( 14, 16)W/D2N8-B, MHC-V12(14, 16)W/D2RN8-B front view 202004 Midea CAC Confidential...
  • Page 13 Safety valve Air purge valve Pump Twout Flow switch Evaporator Manometer Expansion vessel Twin Filter Pressure sensor Filter DC motor High-pressure switch Low-pressure switch Suction temp. sensor Condenser Discharge temp. sensor Single way solenoid valve Capillary Accumulator Compressor 202004 Midea CAC Confidential...
  • Page 14 Provides additional heating capacity when the heating capacity of the heat pump is insufficient due to very low outdoor temperature. Also protects the external water piping from freezing. 10. Water pump: Circulates water in the water circuit. 202004 Midea CAC Confidential...
  • Page 15 3 Refrigerant Flow Diagrams Heating and domestic hot water operation(4,6KW for example) Figure 2-3.1: Refrigerant flow during heating or domestic hot water operation Cooling and defrosting operation(4,6KW for example) Figure 2-3.2: Refrigerant flow during cooling and defrosting operations 202004 Midea CAC Confidential...
  • Page 16 M thermal Mono 202004 Midea CAC Confidential...

  • Page 17: Table Of Contents

    2 Standby Control ..................16 3 Startup Control ..................17 4 Normal Operation Control ............... 19 5 Protection Control ................... 21 6 Special Control ..................25 7 Role of Temperature Sensors in Control Functions ........28 202004 Midea CAC Confidential...

  • Page 18: Stop Operation

    (either manually or when the power has returned following a power outage), the crankcase heater turns on. 2.2 Water Pump Control When the outdoor unit is in standby, the internal and external circulator pumps run continuously. 202004 Midea CAC Confidential...

  • Page 19: Startup Control

    Figures 3-3.1, 3-3.2, 3-3.3 and 3-3.4. Figure 3-3.1: 4-6kW to 12-16kW Compressor startup program when ambient temperature is above 3°C TARGET FREQUENCY TIME Figure 3-3.2: 8-10kW Compressor startup program when ambient temperature is above 11°C TARGET FREQUENCY TIME 202004 Midea CAC Confidential...
  • Page 20 Four-way valve ● ● Notes: Refer to Figure 3-3.1, Figure 3-3.2, Figure 3-3.3 and Figure 3-3.4 in Part 3, 4.2 “Compressor Startup Program”. Refer to Table 3-4.3 in Part 3, 5.6 “Outdoor Fan Control”. 202004 Midea CAC Confidential...

  • Page 21: Normal Operation Control

    The running speed of six-pole compressors (used on all models) in rotations per second (rps) is one third of the frequency (in Hz) of the electrical input to the compressor motor. The frequency of the electrical input to the compressor motors can be altered at a rate of 1Hz per second. 202004 Midea CAC Confidential...
  • Page 22 4.6 Outdoor Fan Control The speed of the outdoor unit fan(s) is adjusted in steps, as shown in Table 3-4.3. Table 3-4.3: Outdoor fan speed steps Fan speed (rpm) Fan speed index 4-6kW 8-10kW 12-14kW 16kW 202004 Midea CAC Confidential...

  • Page 23: Protection Control

    Low pressure protection, error code P0 is displayed Notes: : Suction pressure When the suction pressure drops below 0.14MPa the system displays P0 protection and the unit stops running. When the suction pressure rises above 0.3MPa, the compressor enters re-start control. 202004 Midea CAC Confidential...
  • Page 24 8-10kw 12-16kw 1ph 12-16kw 3ph Current When the compressor current rises above Current the system displays P3 protection and the unit stops running. When the compressor current drops below Current , the compressor enters re-start control. 202004 Midea CAC Confidential...
  • Page 25 30°C, the water side heat exchanger turns off. When water side heat exchanger anti-freeze protection occurs the system displays error code Pb and the unit stops running. 202004 Midea CAC Confidential...
  • Page 26 When the module temperature rises at or above Tf2 the system displays C7 protection and the unit stops running. When the module temperature drops at or below Tf0-1, the compressor enters re-start control. 4-6kW 8-10kW 12-16kW 1ph 12-16kW 3ph 202004 Midea CAC Confidential...

  • Page 27: Special Control

    Electronic expansion valve Fully open ● ● Four-way valve ● ● 6.3 Fast DHW Operation Fast DHW operation is used to quickly meet a requirement for domestic hot water when DHW priority has been set on the 202004 Midea CAC Confidential...
  • Page 28 With the help of hydraulic adapter PCB, totally 8 thermostats can be used at the same time for maximum 8 rooms to control heat pump. Note: M thermal units just have the controlling function, while the mixing valve, water pump of each zone need to be field supplied and connect to M thermal unit. 202004 Midea CAC Confidential...
  • Page 29 TBH is only controlled by M1M2. If dry contract closes, T5<65℃ then TBH opens until water tank temperature reaches 70℃.  For AHS control In heating mode， AHS on/off is only controlled by M1M2. In DHW mode, M1M2 control does not affect AHS on/off. 202004 Midea CAC Confidential...

  • Page 30: Role Of Temperature Sensors In Control Functions

    7 Role of Temperature Sensors in Control Functions Figure 3-7.1: Location of the temperature sensors on 4~16KW unit systems Notes: The names and functions of the temperature sensors labelled 1 to 12 in this figure are detailed in Table 3-6.1. 202004 Midea CAC Confidential...
  • Page 31 Refer to Part 3, 4.6 “Outdoor Fan Control”. 10. Refer to Part 3, 2.2 “Freeze Prevention Control”. Refer to Part 3, 3 “Startup Control”. 11. Refer to Part 3, 6.4 “Fast DHW Operation”. Refer to Part 3, 4.2 “Compressor Output Control”. 202004 Midea CAC Confidential...
  • Page 32 M thermal Mono 202004 Midea CAC Confidential...
  • Page 33 Part 4 Diagnosis and Troubleshooting 1 Outdoor Unit Electric Control Box Layout ..........32 2 Outdoor Unit PCBs ................... 35 3 Error Code Table ..................49 4 Troubleshooting ..................52 5 Appendix to Part 4 ................. 108 202004 Midea CAC Confidential...

  • Page 34: Outdoor Unit Electric Control Box Layout

    1 Outdoor Unit Electric Control Box Layout MHC-V4W/D2N8-B / MHC-V6W/D2N8-B Figure 4-1.1: Electric control box front view Main PCB for refrigerant system Main PCB for hydronic system Main PCB for refrigerant system Inverter module terminal blocks 200204 Midea CAC Confidential...
  • Page 35 Inverter module Outdoor unit power supply terminals Communication terminal blocks MHC-V12W/D2N8-B / MHC-V14W/D2N8-B / MHC-V16W/D2N8-B Figure 4-1.3: Electric control box front view Inverter module Main PCB for refrigerant system terminal blocks Main PCB fort hydronic system 202004 Midea CAC Confidential...
  • Page 36 M thermal Mono MHC-V12W/W/D2RN8-B / MHC-V14W/W/D2RN8-B / MHC-V16W/W/D2RN8-B Figure 4-1.4: Electric control box front view Main PCB for refrigerant system Main PCB for hydronic system Inverter module Outdoor unit power supply Communication terminal blocks terminals 200204 Midea CAC Confidential...

  • Page 37: Outdoor Unit Pcbs

    The locations of each PCB in the outdoor unit electric control boxes are shown in Figures 4-1.1 to 4-1.4 in Part 4, 1 “Outdoor Unit Electric Control Box Layout”. 2.2 Main PCB for Hydronic System Figure 4-2.1: Outdoor unit main PCB for hydronic system 202004 Midea CAC Confidential...
  • Page 38 Feedback port for external temp. switch(shorted in default) Feedback port for temperature switch CN22 Control port for backup heater/booster heater CN41 Port for anti-freeze electric heating tape CN42 Port for anti-freeze electric heating tape CN29 Port for anti-freeze electric heating tape IC39 EEPROM 200204 Midea CAC Confidential...
  • Page 39 M thermal Mono 2.3 Main PCBs for Refrigerant System, Inverter Modules and filter board MHC-V4W/D2N8-B / MHC-V6W/D2N8-B / MHC-V8W/D2N8-B / MHC-V10W/D2N8-B Figure 4-2.2: MHC-V4(6,8,10)W/D2N8-B outdoor unit main PCB for refrigerant system 27 26 25 24 22 21 20 202004 Midea CAC Confidential...
  • Page 40 Port for communication(reserved) Port for communication(reserved) CN33 Port for electrical expansion value CN16 Reserved Port for 4-way value Port for SV6 value Port for compressor electric heating tape 1 CN18 Port for compressor electric heating tape 2 200204 Midea CAC Confidential...
  • Page 41 M thermal Mono Figure 4-2.3: MHC-V4(6)W/D2N8-B outdoor unit inverter module 202004 Midea CAC Confidential...
  • Page 42 Compressor connection port W Output port for +12V/5V CN20 Port for fan CN19 Port for communication with FILTER BOARD CN32 Input port L for rectifier bridge CN502 Input port N for rectifier bridge CN501 EEPROM IC320 200204 Midea CAC Confidential...
  • Page 43 M thermal Mono MHC-V12W/D2N8-B / MHC-V14W/D2N8-B / MHC-V16W/D2N8-B Figure 4-2.4: MHC-V12( 14, 16)W/D2N8-B outdoor unit main PCB for refrigerant system 27 26 25 24 22 21 20 202004 Midea CAC Confidential...
  • Page 44 Port for communication(reserved) Port for communication(reserved) CN33 Port for electrical expansion value CN16 Reserved Port for 4-way value Port for SV6 value Port for compressor electric heating tape 1 CN18 Port for compressor electric heating tape 2 200204 Midea CAC Confidential...
  • Page 45 CN19 Output port for +12V/9V CN20 Port for communication with FILTER BOARD CN32 Port for high pressure switch CN23 Reserved Input port L for rectifier bridge CN501 Input port N for rectifier bridge CN502 EEPROM IC14 202004 Midea CAC Confidential...
  • Page 46 M thermal Mono MHC-V12W/W/D2RN8-B / MHC-V14W/W/D2RN8-B / MHC-V16W/W/D2RN8-B Figure 4-2.6: MHC-V12(14, 16)W/W/D2RN8-B outdoor unit main PCB for refrigerant system 26 25 24 23 22 21 20 19 18 17 16 15 14 200204 Midea CAC Confidential...
  • Page 47 Port for communication XYE CN28 DIP switch S5, S6 Port for communication D1D2E CN37 Port for electrical expansion value CN22 Port for fan 15VDC power supply CN30 Port for fan 310VDC power supply CN53 Port for fan CN107 202004 Midea CAC Confidential...
  • Page 48 Power Input port L3 Input port P_in for IPM module P_in Port for communication with FILTER BOARD Power for PED board CN22 Power for switching power supply Input port for high pressure switch CN23 EEPROM IC25 200204 Midea CAC Confidential...
  • Page 49 CN214 Ground wire Port for communication with FILTER BOARD Power filtering L3 L3’ Power filtering L2 L2’ Power filtering L1 L1’ Power supply port for main control board CN30 Ground wire Ground wire Power supply L1 202004 Midea CAC Confidential...
  • Page 50 By defaulting the units have this coded switch positioned=0, but this corresponds to the Modbus address 16, while the others positions correspond the number, e.g. pos=2 is address 2, pos=5 is address 5. Figure 4-2.9 Rotating switch Figure 4-2.10: Connection Figure 4-2.11: Wiring 200204 Midea CAC Confidential...

  • Page 51: Error Code Table

    PCB User interface and hydronic system Room temperature sensor error Sensor Ta main PCB User interface and refrigerant system DC fan error main PCB User interface and refrigerant system Abnormal main circuit voltage main PCB 202004 Midea CAC Confidential...
  • Page 52 Sensor names in this service manual referring to refrigerant flow is named according refrigerant flow during cooling operation refer to Part 2, 3 “Refrigerant Flow Diagrams”. When the error code appears, the error code corresponding to the error code can be obtained through the H1H2 port by using the host computer to query the wired controller register. 200204 Midea CAC Confidential...
  • Page 53 M thermal Mono 202004 Midea CAC Confidential...

  • Page 54: Troubleshooting

     Power-off the outdoor units before connecting or disconnecting any connections or wiring, otherwise electric shock (which can cause physical injury or death) may occur or damage to components may occur. 200204 Midea CAC Confidential...
  • Page 55  Error code is displayed on hydronic system main control board for refrigerant system and user interface. Possible causes  The wire circuit is short connected or open.  Water flow rate is too low.  Water flow switch damaged. 202004 Midea CAC Confidential...
  • Page 56 Check water pressure on the manometer. If the water pressure is not > 1 bar, water flow is insufficient. Refer to Figure 2-1.2 and 2-1.6 in Part 2, 1 “Layout of Functional Components”. The fuse is labeled 25 in Figure 4-2.1 in Part 4, 2.2 “Main PCB for Hydronic System”. 200204 Midea CAC Confidential...
  • Page 57  Error code is displayed on refrigerant system main control board for refrigerant system and user interface. Possible causes  Power supply phases not connected in correct sequence.  Power supply terminals loose.  Power supply abnormal.  Main PCB damaged. 202004 Midea CAC Confidential...
  • Page 58 Therefore if multiple units are to be used, the phase sequence should be staggered, so that the current is distributed among the three phases equally. Loose power supply terminals can cause the compressors to operate abnormally and compressor current to be very large. 200204 Midea CAC Confidential...
  • Page 59  Communication wiring X Y E terminals misconnected.  Loosened wiring within electric control box.  Interference from high voltage wires or other sources of electromagnetic radiation.  Damaged main PCB or electric control box communication terminals block. 202004 Midea CAC Confidential...
  • Page 60 Measure the resistance among P, Q and E. The normal resistance between P and Q is 120Ω, between P and E is infinite, between Q and E is infinite. Communication wiring has polarity. Ensure that the P wire is connected to P terminals and the Q wire is connected to Q terminals. 200204 Midea CAC Confidential...
  • Page 61  M thermal Mono stops running.  Error code is displayed on hydronic system main control board for refrigerant system and user interface. Possible causes  Temperature sensor not connected properly or has malfunctioned.  Damaged hydronic system main PCB. 202004 Midea CAC Confidential...
  • Page 62 Measure sensor resistance. If the resistance is too low, the sensor has short-circuited. If the resistance is not consistent with the sensor’s resistance characteristics table, the sensor has failed. Refer to Table 4-5.1 or 4-5.3 in Part 4, 5.1 “Temperature Sensor Resistance Characteristics”. 200204 Midea CAC Confidential...
  • Page 63  M thermal Mono stops running.  Error code is displayed on refrigerant system main control board for refrigerant system and user interface. Possible causes  Temperature sensor not connected properly or has malfunctioned.  Damaged refrigerant system main PCB. 202004 Midea CAC Confidential...
  • Page 64 Measure sensor resistance. If the resistance is too low, the sensor has short-circuited. If the resistance is not consistent with the sensor’s resistance characteristics table, the sensor has failed. Refer to Table 4-5.1, and Table 4-5.2 in Part 4, 5.1 “Temperature Sensor Resistance Characteristics” 200204 Midea CAC Confidential...
  • Page 65 Replace hydronic system main PCB Notes: Hydronic system main PCB EEPROM is designated IC18 on the hydronic system main PCB (labeled 29 in Figure 4-2.1 in Part 4, 2.2 “Main PCB for Hydronic System”). 202004 Midea CAC Confidential...
  • Page 66 Provide normal power LED light is OK Voltage of PN is 380V. Check the main board. The inverter board is IGBT voltage is not correct. damaged, change it. The invert board is ok. Check the rectifier bridge. 200204 Midea CAC Confidential...
  • Page 67 “Main PCBs for Refrigerant System, Inverter Modules and Filter Boards”), designed IC23 on the refrigerant system main PCBs (labeled 26 in Figure 4-2.6 in Part 4, 2.2 “Main PCBs for Refrigerant System, Inverter Modules and Filter Boards”). 202004 Midea CAC Confidential...
  • Page 68 GND and 18V is 18V. If one or more of the voltages are not normal, the power supply for main control board for refrigerant system and transformer is abnormal. Measure the voltages of transformer(s) output ports. If the voltages are not normal, the transformer has malfunctioned. 4.11 H1 Troubleshooting Digital display output 200204 Midea CAC Confidential...
  • Page 69 11V and 17V. If one or more of the voltages are not normal, the power supply for main control board for refrigerant system and transformer is abnormal. Measure the voltages of transformer output ports. If the voltages are not normal, the transformer has malfunctioned. 202004 Midea CAC Confidential...
  • Page 70 Possible causes  Power or communication wires not connected properly.  High wind speed.  Fan motor blocked or has failed.  Power supply abnormal.  PFC module damaged.  IPM module damaged.  Main PCB damaged. 200204 Midea CAC Confidential...
  • Page 71 15V, the IPM module on the inverter module is damaged. The fan connections on each type of refrigerant system main control board for refrigerant systemre labelled in Figures 4-2.2, 4-2.4 and 4-2.6 in Part 4, 2.3 “Main PCBs for Refrigerant System, Inverter Modules and Filter Boards”. 202004 Midea CAC Confidential...
  • Page 72  Power supply voltage not within ±10% of rated voltage or a phase is missing.  Outdoor unit powered on immediately after being powered off.  Loosened wiring within electric control box.  High voltage circuit error.  Main PCB damaged. 200204 Midea CAC Confidential...
  • Page 73 High voltage circuit error has occurred, such as the compressor has malfunctioned, the fan motor has Replace or repair the relevant parts short-circuited, or the inverter module has short-circuited Replace refrigerant system main PCB 202004 Midea CAC Confidential...
  • Page 74 The pressure sensor connection on each type of refrigerant system main PCB is labelled in Figures 4-2.2, 4-2.4 and 4-2.6 in Part 4, 2.3 “Main PCBs for Refrigerant System, Inverter Modules and Filter Boards”. Refer also to Part 2, 1 “Layout of Functional Components”. 200204 Midea CAC Confidential...
  • Page 75  Low pressure switch not connected properly or has malfunctioned.  Insufficient refrigerant.  Low pressure side blockage.  Poor evaporator heat exchange in heating mode or DHW mode.  Insufficient water flow in cooling mode.  Main PCB damaged. 202004 Midea CAC Confidential...
  • Page 76 For normal system parameters. Check air side heat exchanger, fan(s) and air outlets for dirt/blockages. Check water side heat exchanger, water piping, circulator pumps and water flow switch for dirt/blockages. 200204 Midea CAC Confidential...
  • Page 77  Error code is displayed on refrigerant system main control board for refrigerant system and user interface. Possible causes  Pressure sensor/switch not connected properly or has malfunctioned.  Excess refrigerant.  System contains air or nitrogen.  High pressure side blockage.  Poor condenser heat exchange.  Main PCB damaged. 202004 Midea CAC Confidential...
  • Page 78 Check water pressure on the manometer. If the water pressure is not > 1 bar, water flow is insufficient. Refer to Figure 2-1.2 and 2-1.6 in Part 2, 1 “Layout of Functional Components”. 200204 Midea CAC Confidential...
  • Page 79  Error code is displayed on refrigerant system main control board for refrigerant system and user interface. Possible causes  Power supply abnormal.  Poor condenser heat exchange.  High pressure side blockage.  Inverter module damaged.  Compressor damaged.  Main PCB damaged. 202004 Midea CAC Confidential...
  • Page 80 The normal resistances of the inverter compressor are 0.7-1.5Ω among U V W and infinite between each of U V W and ground. If any of the resistances differ from these specifications, the compressor has malfunctioned. 200204 Midea CAC Confidential...
  • Page 81  Error code is displayed on refrigerant system main control board for refrigerant system and user interface. Possible causes  Temperature sensor error  High pressure side blockage.  Poor condenser heat exchange.  Main PCB damaged. 202004 Midea CAC Confidential...
  • Page 82 The condenser heat exchange is poor in Inspect the system and fix the error heating mode The water flow rate is not sufficient in Inspect the water system and fix the cooling mode error Replace outdoor main PCB 200204 Midea CAC Confidential...
  • Page 83 High pressure side blockage causes discharge temperature to be higher than normal, discharge pressure to be higher than normal and suction pressure to be lower than normal. Check air side heat exchanger, fan and air outlets for dirt/blockages. Check the water side heat exchanger, water piping, circulator pumps and water flow switch for dirt/blockages. 202004 Midea CAC Confidential...
  • Page 84  Error code is displayed on hydronic system main control board for refrigerant system and user interface. Possible causes  Temperature sensor not connected properly or has malfunctioned.  Water piping contains air.  Insufficient water flow.  Hydronic system main PCB damaged. 200204 Midea CAC Confidential...
  • Page 85 Measure sensor resistance. If the resistance is too low, the sensor has short-circuited. If the resistance is not consistent with the sensor’s resistance characteristics table, the sensor has failed. Refer to Part 2, 1 “Layout of Functional Components” and to Table 5-5.3 in Part 5, 5.1 “Temperature Sensor Resistance Characteristics”. 202004 Midea CAC Confidential...
  • Page 86 MCE error(DC bus low or high voltage protection or software over current protection) Zero speed protection Compressor frequency variation greater than 15Hz within 1 second protection Actual compressor frequency differs from target frequency by more than 15Hz protection 200204 Midea CAC Confidential...
  • Page 87 L9 - Actual compressor frequency differs from target frequency by more than 15Hz Flashes 17 times and stops for 1 second, then repeats protection Figure 4-4.1: LED location of inverter module Inverter Module(4-10KW): LED301/302/303 Inverter Module(12-16KW): LED1/LED2/LED3 202004 Midea CAC Confidential...
  • Page 88 When replacing an inverter module, a layer of thermally conductive silica gel should be painted on the IPM module, IGBT, diode, brigde rectifier (on the reverse side of the inverter module). Refer to Figure 4-4.2. Figure 4-4.2: Replacing an inverter module IGBT diode IGBT diode brigde rectifier 200204 Midea CAC Confidential...
  • Page 89 The normal resistances of the inverter compressor are 0.7-1.5Ω among U V W and infinite between each of U V W and ground. If any of the resistances differ from these specifications, the compressor has malfunctioned. 202004 Midea CAC Confidential...
  • Page 90 When replacing an inverter module, a layer of thermally conductive silica gel should be painted on the PFC and IPM modules (on the reverse side of the inverter module PCB). Refer to Figure 4-4.2. Situation 4: L0 error appears occasionally/irregularly The outdoor unit ventilation is not good Ensure enough space for unit ventilation 200204 Midea CAC Confidential...
  • Page 91 Situation 2: L1 or L2 error appears after the compressor has been running for a period of time and the compressor speed is over 20rps L1 /L2 Relay on outdoor unit main PCB is open Replace the outdoor unit main PCB Replace the inverter module 202004 Midea CAC Confidential...
  • Page 92 Replace inverter module PCB Replace the compressor When replacing an inverter module, a layer of thermally conductive silica gel should be painted on IPM module (on the reverse side of the inverter module PCB). Refer to Figure 4-4.2. 200204 Midea CAC Confidential...
  • Page 93 MCE error(DC bus low or high voltage protection or software over current protection) Zero speed protection Compressor frequency variation greater than 15Hz within one second protection Actual compressor frequency differs from target frequency by more than 15Hz protection 202004 Midea CAC Confidential...
  • Page 94 ① 380-415V AC power supply change to DC power supply after bridge rectifier. ② Contactor is open the current across the PTC to charge capacitor, after 5 seconds the contactor closed. ③ The capacitor output steady 540V DC power supply for inverter module P N terminals. 200204 Midea CAC Confidential...
  • Page 95 When replacing an inverter module, a layer of thermally conductive silica gel should be painted on the IPM module (on the reverse side of the inverter module PCB). Refer to Figure 4-4.2. （ ） ， （ ） Figure 4-4.6: F0 and GND voltage on IC28-1 IC28-4 Vnormal = 5V （ ） （ ） IC28-1 IC28-4 202004 Midea CAC Confidential...
  • Page 96 The normal resistances of the inverter compressor are 0.7-1.5Ω among U V W and infinite between each of U V W and ground. If any of the resistances differ from these specifications, the compressor has malfunctioned. 200204 Midea CAC Confidential...
  • Page 97 Figure 4-4.8: Connection port for inverter module When replacing an inverter module, a layer of thermally conductive silica gel should be painted on the IPM module (on the reverse side of the inverter module PCB). Refer to Figure 4-4.2. 202004 Midea CAC Confidential...
  • Page 98 Use clip-on ammeter to measure the compressor current, if the current is normal indicates the inverter module is failed, if the current is abnormal indicates the compressor has failed. Situation 5: L0 error appears occasionally/irregularly The outdoor unit ventilation is not good Ensure enough space for unit ventilation 200204 Midea CAC Confidential...
  • Page 99 DC voltage between terminal P and N is Check power supply, three phase bridge abnormal rectifier Replace the main PCB Notes: P N +15V terminal on refrigerant system main PCB. Refer to Figure4-4.9. Voltage between N and +15. Refer to Figure4-4.10 202004 Midea CAC Confidential...
  • Page 100 (terminals 1, 2 and 3) in turn. The voltage between terminal 4 and each of terminals 1, 2 and 3 should be infinite. If the voltage is 0, the bridge rectifier has failed. Figure 4-4.11: Bridge rectifier Three phase AC power input DC power output Schematic diagram 200204 Midea CAC Confidential...
  • Page 101 Re-start the unit, use clip-on ammeter to measure the compressor current, if the current is normal indicates the compressor is failed, if the current is abnormal indicates the inverter PCB is failed.. L5/L8/L9 troubleshooting L5/L8/L9 The wire is not connected properly Ensure wire is connected properly Inverter module PCB has malfunctioned Replace inverter module PCB Replace the compressor 202004 Midea CAC Confidential...
  • Page 102  PED PCB failure  M thermal Split stops running.  Error code is displayed on hydronic box main PCB and user interface. Possible causes  Power supply problem.  PED board broken.  IPM module broken. 200204 Midea CAC Confidential...
  • Page 103 Replace PED PCB and power on again. IPM module broken. Replace IPM module and power on again. Notes: PED is port CN22 on the hydronic box main PCB (labeled 11 in Figure 4-2.7: MHA-V12(14,16)W/D2RN8-B outdoor unit inverter module ). 202004 Midea CAC Confidential...
  • Page 104 Measure sensor resistance. If the resistance is too low, the sensor has short-circuited. If the resistance is not consistent with the sensor’s resistance characteristics table, the sensor has failed. Refer to Part 2, 1 “Layout of Functional Components” and to Table 4-5.3 in Part 4, 5.1 “Temperature Sensor Resistance Characteristics”. 200204 Midea CAC Confidential...
  • Page 105  Error code is displayed on refrigerant system main control board for refrigerant system and user interface. Possible causes  Temperature sensor not connected properly or has malfunctioned.  Poor condenser heat exchange.  Fan motor damaged.  Hydronic system main PCB damaged. 202004 Midea CAC Confidential...
  • Page 106 Refer to Part 2, 1 “Layout of Functional Components” and to Table 4-5.1 in Part 4, 5.1 “Temperature Sensor Resistance Characteristics”. Check air side heat exchanger, fan(s) and air outlets for dirt/blockages. 200204 Midea CAC Confidential...
  • Page 107  Error code is displayed on hydronic system main control board for refrigerant system and user interface.  If PP error occurs 3 times then Hb will appear. Possible causes  Temperature sensor not connected properly or has malfunctioned.  4-way valve is blocked or damaged.  Hydronic system main PCB damaged. 202004 Midea CAC Confidential...
  • Page 108 Refer to Part 2, 1 “Layout of Functional Components” and to Table 4-5.1 to 4-5.2 in Part 4, 5.1 “Temperature Sensor Resistance Characteristics”. Restart the unit in cooling mode to change the refrigerant flow direction. If the unit does not operate normally, the 4-way valve is blocked or damaged. 200204 Midea CAC Confidential...
  • Page 109  Temperature collecting plate(Optional) connection wire is not connected.  Temperature collecting plate(Optional) is damaged. Procedure Temperature collecting plate Check the connection line and joint. connection wire is not connected. Temperature collecting plate is Replace temperature collecting plate damaged. 202004 Midea CAC Confidential...

  • Page 110: Appendix To Part 4

    29.528 4.571 1.041 28.026 4.387 1.007 26.608 4.213 0.974 25.268 4.046 0.942 24.003 3.887 0.912 22.808 3.735 0.883 21.678 3.59 0.855 20.61 3.451 0.828 19.601 3.318 0.802 18.646 3.191 0.777 17.743 3.069 0.753 16.888 2.952 0.73 200204 Midea CAC Confidential...
  • Page 111 1.717 115.2 20.46 5.157 1.674 109.8 19.69 5.000 1.632 104.6 18.96 4.849 99.69 18.26 4.703 95.05 17.58 4.562 90.66 16.94 4.426 86.49 16.32 4.294 82.54 15.73 4.167 78.79 15.16 4.045 75.24 14.62 3.927 71.86 14.09 3.812 202004 Midea CAC Confidential...
  • Page 112 178.22 28.269 6.5228 168.31 27.139 6.3114 160.90 26.061 6.1078 152.96 25.031 5.9117 145.45 24.048 5.7228 138.35 23.109 5.5409 131.64 22.212 5.3655 125.28 21.355 5.1965 119.27 20.536 5.0336 113.58 19.752 4.8765 108.18 19.003 4.7251 103.07 18.286 4.5790 200204 Midea CAC Confidential...
  • Page 113 Ver. 2020-04 Commercial Air Conditioner Division Midea Group Add.: Midea Headquarters Building, 6 Midea Avenue, Shunde, Foshan, Guangdong, China Postal code: 528311 Tel: +86-757-26338346; Fax: +86-757-22390205 cac.midea.com / global.midea.com Note: Product specifications change from time to time as product improvements and developments are released and may vary from those in this document.

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