BoilerFaultCodesTechnical description
Overheat lockout
What causes this fault?
This fault occurs when the water inside the heat exchanger exceeds a safe temperature limit, triggering a safety cutout to prevent damage. The most common reasons include a failing circulation pump that isn't moving heat away quickly enough or a blockage in the system pipework. It can also be caused by a faulty internal sensor incorrectly reading the temperature.
This issue often surfaces during the first cold spell of autumn when the heating is turned on after being dormant all summer, which can cause internal pump components to seize.
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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