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Knowledge Hub

Air source heat pump support

Here you’ll find some information on potential Hitachi air source heat pump problems, along with some tips on how to diagnose and repair them.

Ideal control settings

Domestic hot water – continuous.

Heating – manual. This will ensure good hot water and only top up when required. With underfloor heating, it is better to keep the heating at a constant lower temperature for all day comfort rather than allowing the property to cool down and heat up. It will also be more energy efficient.

Controller fault codes

If the system develops a fault, this will be shown on the main Hitachi controller. Normally it will display ‘TEXT **°C’. If a fault is detected it will display ‘FAUL *’.

The number tells the engineer what the fault relates to. Every so often the controller will self-check and you may see it display ‘FAUL 0’. This shows there are no faults and the system is operating properly.

‘FAUL 9’ means it has detected a problem with the heat pump. Quite often this could be air in the system or a blocked filter causing a high-pressure alarm in the heat pump. Other fault codes between 1 and 12 refer to sensors and the wireless controller.

The first action if a fault code appears is to switch the mains power to the Hitachi controller off and on. This will re-set the unit. If the fault code re-appears then you should contact our Technical Support Team.

Need more help to resolve an air source heat pump problem? You can contact our Technical Support Team via or give them a call on 01404 540745 between 8am and 5pm, Monday to Friday.

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