BoilerFaultCodesTechnical description
Manual Lockout. Activated if flow direction is incorrect or casting thermistor exceeds 80C four times. Check system water level, pump, and bypass.
What causes this fault?
This fault occurs when water cannot travel through the boiler fast enough to carry heat away, causing the internal components to get too hot. This is usually caused by a failing pump that can no longer push the water, or a buildup of sludge and debris creating a blockage within the system.
This issue often surfaces in autumn when the heating is turned back on for the first time, as the pump can seize up after sitting idle throughout the 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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