BoilerFaultCodesTechnical description
Safety thermostat (overheat)
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature, triggering a safety switch to cut power. The most common reasons are a pump failure preventing heat from moving away from the boiler, or a blockage such as 'sludge' in the pipework obstructing flow.
This fault often appears during the first few cold days of autumn when a heating system is turned back on after being idle all summer, which can cause 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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