Vaillant Geothermal Heat Pump Error Codes



To call up the Error History, see ⇒ operating instructions. Five types of fault may occur, of which the first four are indicated by fault codes in the display:

  • Faults on components which are connected via eBUS.
  • Faults with a consequent temporary warning message The heat pump remains in operation and is not switched off.
  • Faults with consequent temporary switch-off The heat pump is temporarily switched off and starts running again of its own accord. The fault is displayed and disappears automatically when the cause of the fault is no longer present or has been eliminated.
  • Faults with consequent permanent switch-off The heat pump is permanently switched off. The heat pump can be started again after the cause of the fault has been rectified and the fault reset in the Error History
  • In addition, other types of fault/malfunction may occur in the heat pump or heating system.
Fault CodePossible cause
1XXX address YY not achievable
4XXX Address YY Sensor fault ZZZ
5XXXX setpoint not achieved
26Overheating on compressor pressure side
36Low brine pressure
20Heat source frost protect monitoring source outlet Heat source temperature spread (T3 - T8) > set value "Perm. temp. spread" This fault message is deactivated by default and can only be activated via vrDIALOG parameter "Perm. temp. spread" (20 K spread means deactivated).
21Heat source frost protect monitoring source outlet Source outlet temperature T8 too low (<4 °C)
22Heat source frost protect monitoring source outlet Source outlet temperature T8 too low (< Freeze protect temp. parameter in Menu A4)
23No ground water flow Integrated flow switch does not detect any volume flow
27Coolant pressure too high Heat consumption of heating circuit is too low. The integrated high pressure switch tripped at 3 MPa (30 bar) (g). The heat pump can start again after a 60 minute wait at the earliest.
28Coolant pressure too low Brine side/well water side is supplying too little heat. The integral low pressure switch has tripped at 125 kPa (1.25 bar) (g).
29Coolant pressure outside the range If the error occurs twice in a row the heat pump cannot be started until after 60 min. at the earliest.
32Error heat source sensor T8 Short circuit/disconnection in the sensor
33Error heat circuit pressure sensor Short circuit/disconnection in the pressure sensor
34Error brine pressure sensor (VWS only) Short circuit/disconnection in the pressure sensor
40Error comp outlet sensor T1 Short circuit/disconnection in the sensor
41Error heat source sensor T3 Short circuit/disconnection in the sensor
42Error HP return sensor T5 Short circuit/disconnection in the sensor
43Error HP flow sensor T6 Short circuit/disconnection in the sensor
44Error outdoor sensor AF Short circuit/disconnection in the sensor
45Error DHW tank sensor SP Short circuit/disconnection in the sensor
46Error HB flow sensor VF1 Short circuit/disconnection in the sensor
47Error HB return sensor RF1 Short circuit/disconnection in the sensor
48Error flow sensor VF2 Short circuit/disconnection in the sensor
52Sensors do not match the hydraulic scheme
60Heat source frost protect monitoring source outlet Error 20 has occurred three times in a row
61Heat source frost protect monitoring source outlet Fault 21 has occurred three times in succession.
62Heat source frost protect monitoring source outlet Error 22 has occurred three times in a row
63No ground water flow Fault 23 has occurred three times in succession.
72Flow temperature too high for underfloor heating Flow temperature higher than set value for 15 min. (max. CH temperature + compressor hysteresis + 2 K) ¬ Ch. 9.8,, factory setting: 52 °C).
81Coolant pressure too high Error 27 has occurred three times in a row
83Coolant pressure too low. Check heat source Fault 28 has occurred three times in succession
84Coolant pressure outside the range Error 29 has occurred three times in a row
90Heating system pressure too low Pressure <50 kPa (0.5 bar). Heat pump shuts down and goes into operation automatically when the pressure rises above 70 kPa (0.7 bar).
91Brine pressure too low Pressure < 20 kPa (0.2 bar) Heat pump shuts down and goes into operation automatically when the pressure rises above 40 kPa (0,4 bar).
94Phase loss. Check fuse One or more phases have failed
95Incorrect compressor direction of rotation Correct the phase sequence Phase sequence incorrect
96Coolant circuit pressure sensor fault short-circuit in the pressure sensor
Vaillant Geothermal Heat Pump

Vaillant Geothermal Heat Pump

Fault with permanent switch-off

The heat pump is switched off after the occurrence of a critical fault. After the cause of the faulty has been recti- fied, the heat pump can only be started again by resetting the fault (deleting the Error History)(see Menu I 1). An exception applies in the case of fault 90 and 91. These do not have to be reset. When the cause of the fault has been rectified, the heat pump restarts.




Fault diagnosis and rectification

Risk of damage and personal injury due to incorrect fault diagnosis and improper rectification.

Operations for fault diagnosis and fault rectification must only be performed by an approved heating engineer. Carry out the operations described in a professional manner.

Risk of electric shock. Always switch off all power supplies before starting work on the heat pump. Make sure that they are secured against inadvertent switching on again.

Vaillant Geothermal Heat Pump Service Manual PDF

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