High Lockout
E23 on Vokera Condexa Pro

Your boiler has shut itself down as a safety precaution because it has detected an internal fault that could lead to overheating or unsafe operation.

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

REFHI TOO LOW ERROR Temperature measured not correct

What causes this fault?

This fault occurs when the boiler's internal temperature exceeds safe limits, triggering a safety shutdown to prevent damage. The most common reasons are a failure in the pump preventing water from moving through the system, or a faulty sensor incorrectly reporting an overheat. It can also be caused by a blockage in the heat exchanger or air trapped within the unit.

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

E24View →E20View →E25View →

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