BoilerFaultCodesIdeal H8 Fault Code
The Ideal H8 fault code means: your heat pump has stopped working because it has detected an issue with a internal sensor that monitors the pressure levels within the system.. It appears on 1 Ideal model in our database.
Technical description: High Pressure Sensor Error
What causes the Ideal H8 fault?
This fault occurs when the system's internal safety sensor detects that the pressure levels have exceeded safe operating limits or if the sensor itself has failed. The most common reason is a restriction in the water flow through the unit, often caused by a blockage or a pump failure, preventing heat from being moved away quickly enough. It can also be triggered by an electrical fault where the sensor is unable to send a reliable signal back to the main control board.
This fault is more common during the first cold spells of autumn and winter when the system is under higher load after being idle during the summer.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Ideal models that show the H8 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal H8 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026