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113 

In order to diagnose malfunctions, make sure that there 
are no electrical problems before inspecting the 
refrigeration cycle. 
Such problems include insufficient insulation, problem 
with the power source, malfunction of a compressor and a 
fan. 
The normal pressure of the refrigeration cycle depends 
on various conditions, the standard values for them are 
shown in the table on the right. 

 
 
 
 
 

114 

 

Condition of the  

Air-to-Water Heatpump 

indoor and  

outdoor units 

Heating Mode 

Cooling Mode 

 
 

Low Pressure 

 
 

High Pressure 

 
 

Electric current 

during operation 

 
 

Low Pressure 

 
 

High Pressure 

 
 

Electric current 

during operation 

Water leakage or  

insufficient water flow  

rate in the system 

 

 

 

 

 

 

Excessive amount of 

refrigerant 

 

 

 

 

 

 

Inefficient compression 

 

 

 

 

 

 

Insufficient refrigerant 

(gas leakage) 

 

 

 

 

 

 

Outdoor heat exchange 

deficiency 

 

 

 

 

 

 

Clogged expansion valve  

or Strainer 

 

 

 

 

 

 

 

  Carry out the measurements of pressure, electric current, and temperature fifteen minutes after an operation is 

started. 

115 

  When abnormality occur during operation, the system will stop operation, and OFF/ON control panel LED will 

blink and error code will display on the control panel Timer display LCD. 

  Even error code is reset by turning OFF power supply or by pressing ERROR RESET button, if the system 

abnormality is still un-repaired, system will again stop operation, and OFF/ON control panel LED will again blink. 

  The error code will store in IC memory. 
 
  To check the error code 

1  When an abnormality occurs, system will stop operation and OFF/ON control panel LED will blink. 
2  Error code of the abnormality will display on the control panel Timer display LCD. 
3  To determine the abnormality description, the error code table needs to be referred. 

 
  To display past/last error code 

1  Turn ON power supply. 
2  Press and hold the CHECK button for more than 5 seconds to enter status mode. 
3  Press the SEARCH DOWN/UP button to retrieve past/last error code. 
4  Press the CANCEL button or wait 30 seconds to exit status mode. 

 

  To permanently delete error code from IC memory 

1  Turn ON power supply. 
2  Press and hold the ERROR RESET button for more than 8 seconds till a beep sound is heard. 

 

OPERATION

ACTUAL

HEATER

BOOSTER

QUIET

SETTING

STATUS

SERVICE

AUTO

HEAT

COOL

TANK

HEATER

FORCE

°C

°C

ON
OFF

MON TUE WED THU FRI SAT SUN

hr

hr

kwh

SEARCH

Downward/Upward

Button

CANCEL

Button

ERROR

RESET

Button

CHECK Button

 

116 

 

H00 

No abnormality detected 

— 

— 

H12 

Indoor/Outdoor capacity unmatched 

90s after power supply 

  Indoor/outdoor connection wire 

  Indoor/outdoor PCB 
  Specification and combination table in 

catalogue 

H15 

Outdoor compressor temperature sensor 
abnormality 

Continue for 5 sec. 

  Compressor temperature sensor 

(defective or disconnected) 

H20 

Water pump abnormality 

Continue for 10 sec. 

  Indoor PCB 

  Water pump (malfunction) 

H23 

Indoor refrigerant liquid temperature 
sensor abnormality 

Continue for 5 sec. 

  Refrigerant liquid temperature sensor 

(defective or disconnected) 

H27 

Service valve error 

Continue for 5 minutes 

  High pressure sensor (defective or 

disconnected) 

H42 

Compressor low pressure abnormality 

— 

  Outdoor pipe temperature sensor 

  Clogged expansion valve or strainer 

  Insufficient refrigerant 

  Outdoor PCB 
  Compressor 

H62 

Water flow switch abnormality 

Continue for 1 min. 

  Water flow switch 

H64 

Refrigerant high pressure abnormality 

Continue for 5 sec. 

  Outdoor high pressure sensor  

(defective or disconnected) 

H65 

Deice circulation error 

Continue for 10 sec. 

  Water flow switch sensor (defective or 

disconnected) 

  Water pump malfunction 

  Buffer tank (is used) 

H70 

Back-up heater OLP abnormality 

Continue for 60 sec. 

  Back-up heater OLP 

(Disconnection or activated) 

H72 

Tank sensor abnormal 

Continue for 5 sec. 

  Tank sensor 

H76 

Indoor - control panel communication 
abnormality 

— 

  Indoor - control panel  

(defective or disconnected) 

H90 

Indoor/outdoor abnormal communication

> 1 min after starting operation

  Internal/external cable connections 

  Indoor/Outdoor PCB 

H91 

Tank heater OLP abnormality 

Continue for 60 sec. 

  Tank heater OLP  

(Disconnection or activated) 

H95 

Indoor/Outdoor wrong connection 

— 

  Indoor/Outdoor supply voltage 

H98 

Outdoor high pressure overload 
protection 

— 

  Outdoor high pressure sensor 

  Water pump or water leakage 

  Clogged expansion valve or strainer 
  Excess refrigerant 

  Outdoor PCB 

H99 

Indoor heat exchanger freeze prevention

— 

  Indoor heat exchanger 
  Refrigerant shortage 

F12 

Pressure switch activate 

4 times occurrence within 20 
minutes 

  Pressure switch 

F14 

Outdoor compressor abnormal revolution

4 times occurrence within 20 
minutes 

  Outdoor compressor 

F15 

Outdoor fan motor lock abnormality 

2 times occurrence within 30 
minutes 

  Outdoor PCB 
  Outdoor fan motor 

F16 

Total running current protection 

3 times occurrence within 20 
minutes 

  Excess refrigerant 
  Outdoor PCB 

F20 

Outdoor compressor overheating 
protection 

4 times occurrence within 30 
minutes 

  Compressor tank temperature sensor 
  Clogged expansion valve or strainer 

  Insufficient refrigerant 

  Outdoor PCB 

  Compressor 

F22 

IPM (power transistor) overheating 
protection 

3 times occurrence within 30 
minutes 

  Improper heat exchange 

  IPM (Power transistor) 

F23 

Outdoor Direct Current (DC) peak 
detection 

7 times occurrence 
continuously 

  Outdoor PCB 

  Compressor 

F24 

Refrigeration cycle abnormality 

2 times occurrence within 20 
minutes 

  Insufficient refrigerant 

  Outdoor PCB 
  Compressor low compression 

F25 

Cooling/Heating cycle changeover 
abnormality 

4 times occurrence within 30 
minutes 

  4-way valve 
  V-coil 

F27 

Pressure switch abnormality 

Continue for 1 min. 

  Pressure switch 

F30 

Water outlet sensor 2 abnormality 

Continue for 5 sec. 

  Water outlet sensor 2 (defective or 

disconnected)