BoilerFaultCodesTechnical description
Safety thermostat operated
What causes this fault?
This fault occurs when the water inside the boiler gets too hot, triggering a safety switch to prevent damage. The most common reasons are a pump failure that stops water from moving or a blockage in the system pipes that traps heat inside the heat exchanger.
This issue is more frequent when the heating is first turned on in autumn, as circulation pumps can seize up after being inactive 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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