SolarpunkHomes
Sign inCall us · +44 7510 081687
Heat pumps
Heat pumps · Error codes

Ariston heat pump error codes

Ariston · A niche brand in the UK. 96 codes across 2 product families, each taken from the manufacturer’s manuals. Ariston technical support ↗

Find a Ariston engineer →96 codes · reviewed 23 September 2026

Filter by product family

Type the code on your display or a word from its meaning. Each code opens its own page with what it means, whether it is safe and what you can check.

96 codes

CodeMeaningStops?Homeowner check?
2P2
Thermal cleanse not complete - sanitisation temperature not reached in 6 h
NoYes
2P3
DHW setpoint not reached in boost
NoYes
2P4
Electric heater thermostat (manual reset)
PartlyYes
2P5
Electric heater thermostat (automatic reset)
PartlyYes
2P7
Precirculation error
Not statedYes
2P8
Low pressure warning
NoYes
2P9
SG ready input configuration error
Not statedYes
9E5
High-pressure pressure switch intervention
YesYes
9E8
Low-pressure pressure switch error with compressor OFF
YesYes
9E9
Klixon error with compressor OFF
YesYes
9E18
ST1 safety thermostat error
YesYes
9E21
Low refrigerant charge error
Not statedYes
9E22
Machine empty error
YesYes
9E24
EXV seized up error
Not statedYes
9E28
High pressure protection
Not statedYes
9E29
High pressure protection
YesYes
9E31
Compressor thermostat protection
Not statedYes
9E32
Compressor thermostat protection
YesYes
9E34
Low-pressure protection
Not statedYes
9E35
Low-pressure protection
YesYes
9E36
Compressor phases current imbalance
Not statedYes
9E37
Compressor phases current imbalance
YesYes
9E38
Excessively steep compressor current variation
Not statedYes
9E39
Excessively steep compressor current variation
YesYes
114
Outside temperature not available - temperature control activation based on the external sensor
PartlyYes
730
Buffer high probe error - buffer filling inhibited
PartlyYes
731
Buffer overtemperature - buffer filling inhibited
PartlyYes
732
Buffer low probe error - buffer filling inhibited
PartlyYes
902
System flow sensor damaged
Not statedYes
905
HP compressor mismatch error
Not statedYes
906
HP fan mismatch error
Not statedYes
907
HP 4-way valve mismatch error
Not statedYes
908
Expansion valve mismatch error
Not statedYes
909
Fan off and heat pump on
Not statedYes
910
Inverter-TDM communication error
YesYes
912
4-way valve error
YesYes
913
LWT sensor error
YesYes
914
TR sensor error
YesYes
917
Freeze error
YesYes
918
Pump down error
YesYes
921
Error electricity/gas cost ratio
Not statedYes
922
Freeze error
Not statedYes
923
Heating circuit pressure error
YesYes
924
Communication error (TDM board - Energy Manager); 'HP communication error' in the user manual
YesYes
925
Boiler not present
Not statedYes
927
AUX inputs correspondence error
Not statedYes
928
Energy supply shutdown configuration error (hybrid manual: 'External lockout configuration mismatch')
Not statedYes
931
Inverter error (see inverter sub-codes 1-28)
YesYes
931-1
Inverter error sub-code 1: Inverter output current sensor error
YesYes
931-2
Inverter error sub-code 2: DC bus capacitors pre-charge error
YesYes
931-3
Inverter error sub-code 3: Inverter input voltage sensor error
YesYes
931-4
Inverter error sub-code 4: Inverter heat sink temperature sensor error
YesYes
931-5
Inverter error sub-code 5: DSP&MCU communication error
YesYes
931-6
Inverter error sub-code 6: Inverter input AC overcurrent
YesYes
931-7
Inverter error sub-code 7: Inverter PFC current sensor error
YesYes
931-8
Inverter error sub-code 8: Inverter PFC temperature sensor error
YesYes
931-9
Inverter error sub-code 9: Corrupt EPROM
YesYes
931-10
Inverter error sub-code 10: PFC HW overcurrent
YesYes
931-11
Inverter error sub-code 11: PFC SW overcurrent
YesYes
931-12
Inverter error sub-code 12: Inverter PFC overvoltage
YesYes
931-13
Inverter error sub-code 13: A/D error
YesYes
931-14
Inverter error sub-code 14: Addressing error
YesYes
931-15
Inverter error sub-code 15: Compressor inverse rotation
YesYes
931-16
Inverter error sub-code 16: No current variation on compressor phase
YesYes
931-17
Inverter error sub-code 17: Misalignment between real and calculated speed
YesYes
931-18
Inverter error sub-code 18: Vaux inverter error
YesYes
931-19
Inverter error sub-code 19: Vstep Inverter/Control Board error
YesYes
931-20
Inverter error sub-code 20: Inrush circuit error
YesYes
931-21
Inverter error sub-code 21: PFC inverter error
YesYes
931-22
Inverter error sub-code 22: DC bus overcurrent
YesYes
931-23
Inverter error sub-code 23: Inverter module error
YesYes
931-24
Inverter error sub-code 24: Compressor loss of synchronism
YesYes
931-25
Inverter error sub-code 25: PCB overheating
YesYes
931-26
Inverter error sub-code 26: HW interruption
YesYes
931-27
Inverter error sub-code 27: Absence of configuration
YesYes
931-28
Inverter error sub-code 28: SW error
YesYes
933
Flow sensor overtemperature
Not statedYes
934
DHW tank sensor damaged
PartlyYes
935
Tank overtemperature
PartlyYes
936
Floor thermostat 1 error
PartlyYes
937
No circulation error
Not statedYes
938
Anode fault
Not statedYes
940
Hydraulic scheme not defined
YesYes
947
4-way valve error
Not statedYes
950
Compressor delivery sensor error
YesYes
951
TD sensor error
Not statedYes
955
Water flow check error
Not statedYes
956
HP compressor model mismatch
Not statedYes
957
HP fan model mismatch
Not statedYes
960
HP EWT sensor error
YesYes
962
Defrost energy
YesYes
968
ATGBUS TDM-EM communication error
YesYes
970
Aux. pump configuration mismatch
Not statedYes
994
Low refrigerant charge error
Not statedYes
997
Compressor overcurrent
Not statedYes
998
Compressor overcurrent
YesYes