BoilerFaultCodesTechnical description
Safety Thermostat Operated
What causes this fault?
This fault occurs when the water inside the boiler reaches an unsafe temperature, triggering a safety switch to kill the power. The most common reasons are a pump failure that prevents water from moving, or a blockage in the system that stops heat from being carried away from the burner.
This fault is more common in autumn when heating is turned on for the first time after summer, as internal pump parts can seize up from lack of use.
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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