BoilerFaultCodesIdeal H3 Fault Code
The Ideal H3 fault code means: your heat pump has detected a problem with a temperature sensor inside the unit, causing the system to stop working to prevent any damage.. It appears on 1 Ideal model in our database.
Technical description: Plate Heat Exchanger Inlet Refrigerant Thermistor (T2B) Error
What causes the Ideal H3 fault?
This fault occurs when the system loses its ability to accurately measure the temperature of the refrigerant as it enters the heat exchanger. This usually happens because the internal sensor has developed an electrical fault or the wiring has become loose or damaged, preventing the main control board from monitoring the unit's safety and efficiency.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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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 7 July 2026