High
AL20 on Vokera Mynute 23E

Your boiler has shut down because it has detected a temperature that is too high, often caused by a blockage or a pump failure.

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.

What the manual says

Manufacturer manual

Limit thermostat fault

From this model's manual
Verified against the Vokera Mynute 10e installation & service manual, page 28.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This fault occurs when the water inside the boiler exceeds a safe temperature, triggering a safety switch to shut the system down. The most common reasons are a pump that has stopped moving water around the system or a blockage in the heat exchanger that prevents heat from escaping.

This fault is more frequent when you first turn the heating back on in autumn, as circulating pumps often seize up after being inactive all summer.

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

AL21View →AL28View →AL60View →

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