BoilerFaultCodesYour boiler has shut down because a built-in safety sensor or an external monitoring device has detected a problem that prevents the system from running safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: External device fault (UHT/CPA)
What causes this fault?
This fault occurs when an external safety component, such as a condensate pump or an overheat thermostat, sends a signal to the boiler to shut down for safety. The most common reason is that the condensate pump has failed or is full of water, triggering a cut-off switch to prevent a leak or internal damage. It can also be caused by a loose wire or a fault in the safety sensor itself.
This fault is more common during the winter months, as frozen external drain pipes can cause the condensate pump to overflow and trigger the safety shutdown.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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