Installation Guide for AU08NFKERA

Installation Guide for AU08NFKERA

Brand: MRV

Category: Air Conditioner

Document Type: Installation Guide

Language: EN

Uploaded: Nov. 21, 2025, 9:21 p.m.

  • The MRV S is a "simultaneous control" type where all indoors must heat or cool simultaneously.
  • Before startup, the unit should be electrified for over 12 hours to protect the compressor.
  • If not used for a long time, cut off the power to save energy.
  • The appliance is not intended for use by persons (including children) with reduced physical, sensory or mental capabilities, or lack of experience and knowledge, unless supervised.
  • Children should be supervised to ensure they do not play with the appliance.
  • Keep the appliance and its cord out of reach of children under 8 years.

Operating Range of Air Conditioner:

  • Cooling dry: Indoor: 18-32°C DB, 14-23°C WB. Outdoor: -5-48°C DB, not specified WB.
  • Heating: Indoor: 15-27°C DB, not specified WB. Outdoor: -20-27°C DB, 15.5°C WB.

Troubleshooting and error codes

Failure code display on the outdoor digital display board Failure code definition Failure code definition Remarks
20-0 Defrosting temp. sensor (Te) failure Continuous disconnect for 60 seconds or short circuit, failure alarm Resumable
21 Ambient temp. sensor (Ta) failure Continuous disconnect for 60 seconds or short circuit, failure alarm Resumable
22 Suction temp. sensor (Ts) failure Continuous disconnect for 60 seconds or short circuit, failure alarm Resumable
23 Discharge temp. sensor (Td) failure Continuous disconnect for 60 seconds or short circuit, failure alarm Resumable
26-0 Communication failure with indoor units No indoor units connection can be detected for continuous 200 cycles. Resumable
26-1 Communication failure with indoor units It was detected that the number of indoor units was less than the set number for 300 seconds. Resumable
26-2 Communication failure with indoor units It was detected that the number of indoor units was more than the set number for 300 seconds. Resumable
28 Discharge pressure sensor (Pd) failure Continuous disconnect for 60 seconds or short circuit, failure alarm. Resumable
29 Suction pressure sensor (Ps) failure Continuous disconnect for 60 seconds or short circuit, failure alarm. Resumable
30 High pressure switch (HPS) failure When the high pressure switch is disconnected, failure alarm. When the high pressure switch is closed, failure removed. Failure is locked if it occurs 3 times in one hour. Once failure locked, un-resumable.
33 EEPROM failure Oudoor unit EEPROM failure Un-resumable
34 Discharge temp. too high (Td) Td≥[115]°C,failure alarm; Td≤[85]°C,failure removed. Failure is locked if it occurs 3 times in one hour. Once failure locked, un-resumable
35 4-way valve revering failure After the compressor starts, it runs continuously for 10 minutes, if the four-way valve does not reverse failure alarm. The failure will be removed after 3 minutes. Failure is locked if it occurs 3 times in one hour. Once failure locked, un-resumable
39-0 Suction pressure (Ps) too low (1) Cooling: Ps≤0.05 MPa or Ps≤0.1MPa for 5 consecutive minutes, failure alarm. Ps≥0.25MPa, failure removed. (2) Heating: Ps≤0.03Mpa or Ps≤0.05MPa for 5 consecutive minutes, failure alarm. Ps≥0.2MPa, failure removed. Failure is locked if it occurs 3 times in one hour. Once failure locked, un-resumable.
39-1 Compression ratio (ε)too high compression ratio (ε) ≥12.0 for 5 consecutive minutes, failure alarm. The failure will be removed after 3 minutes. Failure is locked if it occurs 4 times in 2 hours. Once failure locked, un-resumable.
40 Discharge pressure (Pd) too high Pd≥4.15MPa or Pd≥3.9MPa for 5 consecutive minutes, failure alarm. Pd ≤3.3MPa, failure removed. Failure is locked if it occurs 3 times in one hour. Once failure locked, un-resumable.
43 Discharge temp. too low protection(Td) TdSH ≤ 10°C for 5 consecutive minutes, failure alarm. After the oil temperature is satisfied, the failure will be removed. Failure is locked if it occurs 3 times in one hour. Once failure locked, un-resumable.
46 Communication failure with inverter module No module board signal is received within 30 seconds or data error.It will be automatically restored after receiving correctly. Resumable
51-0 LEVa over current LEV driver chip detection Resumable
51-2 LEVb over current LEV driver chip detection Resumable
52-0 LEVa circuit open failure LEV driver chip detection Resumable
52-2 LEVb circuit open failure LEV driver chip detection Resumable
53 CT current too low or current sensor failure 1. When the compressor runs continuously for 1 minute, the compressor frequency ≥50 Hz for 5 minutes. If the current sensor sampling value is less than 10, failure alarm. The failure will be removed after 3 minutes. 2. When the compressor stops, the failure will alarm if CT > 6A lasts for 3min. The failure will be removed after 3 minutes. Resumable
58 Tsco temp. sensor failure Continuous disconnect for 60 seconds or short circuit, failure alarm. Resumable
59 Tliqsc temp. sensor failure Continuous disconnect for 60 seconds or short circuit, failure alarm. Resumable
64 CT value too high When the CT current exceeds the specified value for 5 consecutive seconds, failure alarm. The failure will be removed after 3 minutes. Failure is locked if it occurs 3 times in one hour. Once failure locked, un-resumable.
71-0 DC Fan1 failure The failure will alarm when it runs below 20 rpm for 40 seconds or below 20% of the target value for 2 minutes. The failure will be removed after 3 minutes. Failure is locked if it occurs 3 times in one hour. Once failure locked, un-resumable.
71-1 DC Fan2 failure The failure will be removed after 3 minutes. Failure is locked if it occurs 3 times in one hour. Once failure locked, un-resumable.
78 Lack of refrigerant 1.Cooling: Ps≤0.2MPa for 30 consecutive minutes, failure alarm. Ps≥0.3MPa for 30 consecutive minutes, failure removed. 2.Heating:Both LEVa equals to 470pls and Ts-Ps≥20°C for 60 consecutive minutes, failure alarm. Ps≥0.2MPa for 30 consecutive minutes, failure removed. Resumable
81 Inverter temp. too high Inverter temp.≥90℃, failure alarm. Inverter temp. ≤70°C, failure removed. Failure is locked if it occurs 3 times in one hour. Once failure locked, un-resumable.
82 Compressor current protection When the compressor current exceeds the specified value for 5 consecutive seconds, failure alarm. The failure will be removed after 3 minutes. Failure is locked if it occurs 3 times in one hour. Once failure locked, un-resumable.
83 Model setting error Model setting does not match the outdoor unit. Once failure locked, un-resumable.
110 The inverter module over current (hardware) Module hardware over current. Failure is locked if it occurs 3 times in one hour. Instantaneous over current of hardware at rectifier side of inverter module. Failure is locked if it occurs 3 times in one hour. Once failure locked, un-resumable.
111 Compressor out of control During start-up or operation, the rotor position cannot be detected for 6 consecutive times, failure alarm. The inverter PCB will be automatic recovery after compressor stops for 5 seconds.
112 The temp. of the module fin is too high The temp. of the module fin≥94°C, failure alarm. The temp. of the module fin < 94°C, the inverter PCB will be automatic recovery.
114 The inverter input power voltage is abnormal The voltage < DC420V, failure alarm. The voltage > DC420V, the inverter PCB will be automatic recovery. The voltage > DC642V, failure alarm. The voltage < DC642V, the inverter PCB will be automatic recovery. The power supply of inverter is interrupted instantaneously.
116 Abnormal communication between the inverter PCB and the control PCB If no communication signal is detected for 30 seconds, failure alarm.After detection, inverter PCB will recover immediately. Resumable
117 The inverter module over current (software) Module rectifier side software instantaneous overcurrent Module overload Module software over current
118 Compressor startup failed The compressor failed to start continuously for 5 times.
119 Current detection circuit failure The module rectifier side current detection circuit is abnormal. The sensor used for current detection of inverter controller is abnormal, disconnected or connected incorrectly.
121 Power supply of inverter module board is abnormal Power supply of inverter board is broken down instantly.
122 The temp. sensor of inverter is abnormal. The resistance of inverter temperature sensor is abnormal or not connected.
555.0 Standby state of capacity over-matched The ratio of indoor capacity to outdoor capacity is over 130%.
555.1 Heating at high ambient temp. Ta>27°C, the indoor units standby when they are running in heatling mode. Resumable
555.3 Cooling at ambient temp. too high or too low Ta>54°C or Ta<-10°C, the indoor units standby when they are running in cooling mode. Resumable
555.4 Oil temp. preheating The oil temperature does not meet the starting conditions of the system.
555.b The running mode of outdoor unit does not match with the indoor units. The outdoor unit maybe setted to cooling only or heating only.
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