BoilerFaultCodesTechnical description
High limit thermostat fault
What causes this fault?
This fault occurs when the internal temperature of the boiler exceeds a safe limit, triggering a safety sensor to cut the power to prevent damage. The most common reasons are a blockage in the system or a pump failure, which stops the water from moving quickly enough to carry heat away from the burner.
This issue often appears during the first cold spell of autumn when the heating is turned back on after months of disuse, which can cause internal parts like the pump 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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