High Lockout
E3 on Ideal HP290

Your system's main temperature sensor is sending incorrect information, which means your heating might not work efficiently or at all.

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

Header Thermistor (T1) Error (for Hybrid/Cascade)

What causes this fault?

This fault occurs when the sensor responsible for monitoring the temperature of the water entering your heating system fails or sends an impossible reading. The most common reason is a physical failure of the thermistor itself, though it can also be caused by loose wiring or a communication error within the main control board. Because the boiler no longer knows the exact temperature of the water, it shuts down as a safety precaution to prevent overheating.

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 →E4View →

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