High Lockout
E4 on Ideal HP290

Your heat pump has stopped making hot water because the sensor that monitors your cylinder's temperature is no longer communicating correctly.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

DHW Cylinder Thermistor (T5) Error

What causes this fault?

This fault occurs when the main control board loses the electrical signal from the sensor inside your hot water tank. This usually happens because the sensor has failed internally due to age or because the wiring connecting the tank to the heat pump unit has become loose or damaged. Without this information, the system shuts down as a safety precaution because it cannot monitor how hot the water is getting.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

E1View →E2View →E3View →

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