BoilerFaultCodesIdeal H3 Fault Code
The Ideal H3 fault code means: your boiler has detected that the water temperature has reached a dangerously high level, causing it to shut down to prevent damage.. It appears on 2 Ideal models in our database.
Technical description: ALTERNATING 'H' '3' GO TO FRAME 92
What causes the Ideal H3 fault?
This fault occurs when the water inside the heat exchanger or the pipework gets too hot, triggering a safety shut-off to protect the boiler. The most common reasons are a failed pump that isn't moving water through the system fast enough, or a blockage caused by a build-up of sludge and debris. It can also be caused by a sensor that has become faulty and is sending the wrong temperature reading to the main control board.
This fault is often seen at the start of winter when the heating is turned on for the first time after summer, as pumps can seize up during long periods of inactivity.
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 H3 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal H3 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