Daikin
The Daikin Altherma 3 R W is a split air source heat pump available in 4kW, 6kW, and 8kW capacities, using R32 refrigerant and capable of 65°C flow temperatures.
The Daikin Altherma 3 R W is a split air source heat pump designed for domestic heating and hot water in the UK. Available in 4kW, 6kW, and 8kW capacities, this R32 refrigerant-based system offers a maximum flow temperature of 65°C and operates down to -25°C ambient. This reference provides technical specifications, fault codes, and compatibility information for heating engineers working with the Altherma 3 R W series.
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Full technical specifications extracted from the manufacturer brochure. Empty sections are hidden.
The Daikin Altherma 3 R W series comprises split air source heat pumps suitable for a range of UK residential applications. Models are available with nominal heating capacities of 4kW, 6kW, and 8kW, all operating on a single-phase 230V, 50Hz electrical supply. These units utilise R32 refrigerant, known for its lower Global Warming Potential compared to previous generations. The system is designed to deliver a maximum flow temperature of 65°C, maintaining performance in outdoor temperatures as low as -25°C.
Hydraulically, the Altherma 3 R W requires a minimum water flow rate of 12 litres per minute and can operate at a maximum pressure of 4 bar. Defrosting is managed automatically via a reverse cycle method, ensuring continuous operation. The indoor unit weighs 42kg and features quiet mode capability. Installation requires specific clearances: 250mm on sides, 350mm front, 250mm above, and 250mm behind the outdoor unit.
Every fault code listed in the manufacturer brochure, with likely causes and engineer actions. Each code has a permalink — paste a URL like https://www.boilertag.com/heat-pumps/daikin/altherma-3-r-w#fault-7h-01 to jump straight to the entry.
| Code | Meaning | Details |
|---|---|---|
| 7H-01 | Water flow problem | — |
| 7H-04 | Water flow problem during domestic hot water production | — |
| 7H-05 | Water flow problem during heating/sampling | — |
| 7H-06 | Water flow problem during cooling/defrost | — |
| 80-01 | Returning water temperature sensor problem | — |
| 81-00 | Leaving water temperature sensor problem | — |
| 89-01 | Heat exchanger frozen (during defrost) | — |
| 89-02 | Heat exchanger frozen (not during defrost) | — |
| 89-03 | Heat exchanger frozen (during defrost) | — |
| 8F-00 | Abnormal increase outlet water temperature (DHW) | — |
| 8H-00 | Abnormal increase outlet water temperature | — |
| 8H-01 | Overheating mixed water circuit | — |
| 8H-02 | Overheating mixed water circuit (thermostat) | — |
| 8H-03 | Overheating water circuit (thermostat) | — |
| A1-00 | Zero cross detection problem | — |
| A5-00 | OU: High pressure peak cut / freeze protection problem | — |
| AA-01 | Backup heater overheated | — |
| AC-00 | Booster heater overheated | — |
| AH-00 | Tank disinfection function not completed correctly | — |
| AJ-03 | Too long DHW heat-up time required | — |
| C0-00 | Flow sensor malfunction | — |
| C4-00 | Heat exchanger temperature sensor problem | — |
| C5-00 | Heat exchanger thermistor abnormality | — |
| CJ-02 | Room temperature sensor problem | — |
| E1-00 | OU: PCB defect | — |
| E2-00 | Leakage current detection error | — |
| E3-00 | OU: Actuation of high pressure switch (HPS) | — |
| E3-24 | High pressure switch abnormality | — |
| E4-00 | Abnormal suction pressure | — |
| E5-00 | OU: Overheat of inverter compressor motor | — |
| E6-00 | OU: Compressor startup defect | — |
| E7-00 | OU: Malfunction of outdoor unit fan motor | — |
| E8-00 | OU: Power input overvoltage | — |
| E9-00 | Malfunction of electronic expansion valve | — |
| EA-00 | OU: Cool/heat switchover problem | — |
| EC-00 | Abnormal increase tank temperature | — |
| EC-04 | Tank preheating | — |
| F3-00 | OU: Malfunction of discharge pipe temperature | — |
| F6-00 | OU: Abnormal high pressure in cooling | — |
| FA-00 | OU: Abnormal high pressure, actuation of HPS | — |
| H0-00 | OU: Voltage/current sensor problem | — |
| H1-00 | External temperature sensor problem | — |
| H3-00 | OU: Malfunction of high pressure switch (HPS) | — |
| H5-00 | Malfunction of compressor overload protection | — |
| H6-00 | OU: Malfunction of position detection sensor | — |
| H8-00 | OU: Malfunction of compressor input (CT) system | — |
| H9-00 | OU: Malfunction of outdoor air thermistor | — |
| HC-00 | Tank temperature sensor problem | — |
| HC-01 | Second tank temperature sensor problem | — |
| HJ-10 | Water pressure sensor abnormality | — |
| J3-00 | OU: Malfunction of discharge pipe thermistor | — |
| J6-00 | OU: Malfunction of heat exchanger thermistor | — |
| J6-07 | OU: Malfunction of heat exchanger thermistor | — |
| JA-00 | OU: Malfunction of high pressure sensor | — |
| L1-00 | Malfunction of INV PCB | — |
| L3-00 | OU: Electrical box temperature rise problem | — |
| L4-00 | OU: Malfunction of inverter radiating fin temperature rise | — |
| L5-00 | OU: Inverter instantaneous overcurrent (DC) | — |
| L8-00 | Malfunction triggered by a thermal protection in the inverter PCB | — |
| L9-00 | Prevention of compressor lock | — |
| LC-00 | Malfunction in communication system of outdoor unit | — |
| P1-00 | Open-phase power supply imbalance | — |
| P3-00 | Abnormal direct current | — |
| P4-00 | OU: Malfunction of radiating fin temperature sensor | — |
| PJ-00 | Capacity setting mismatch | — |
| U0-00 | OU: Shortage of refrigerant | — |
| U1-00 | Malfunction by reverse phase/open-phase | — |
| U2-00 | OU: Defect of power supply voltage | — |
| U3-00 | Underfloor heating screed dryout function not completed correctly | — |
| U4-00 | Indoor/outdoor unit communication problem | — |
| U5-00 | User interface communication problem | — |
| U7-00 | OU: Transmission malfunction between main CPU-INV CPU | — |
| U8-01 | Connection with LAN adapter lost | — |
| U8-02 | Connection with room thermostat lost | — |
| U8-03 | No connection with room thermostat | — |
| U8-04 | Unknown USB device | — |
| U8-05 | File malfunction | — |
| U8-07 | P1P2 communication error | — |
| UA-00 | Indoor unit, outdoor unit matching problem | — |
| UA-16 | Extension/hydro communication problem | — |
| UA-17 | Tank type problem | — |
| UA-21 | Extension/hydro mismatch problem | — |
| UF-00 | Reversed piping or bad communication wiring detection | — |
Patterns that group across the manufacturer's fault-code table. Each entry links to the full code listing further down the page.
Triggered by fault code 7H-01.
Triggered by fault code 7H-04.
Triggered by fault code 7H-05.
Triggered by fault code 7H-06.
Triggered by fault code 80-01.
Common questions from engineers and homeowners about the Daikin Altherma 3 R W.
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Specifications on this page are extracted from the manufacturer brochure. Always cross-check against the latest datasheet before commissioning or quoting. Last updated 28 June 2026.