BoilerFaultCodesTechnical description
Overheat thermostat has operated or primary flow switch has failed to operate
What causes this fault?
This fault occurs when the water inside the boiler reaches an unsafe temperature, triggering a safety sensor to shut the system down to prevent damage. The most common reasons are a pump failure that stops water from moving or a blockage in the pipework preventing heat from escaping the boiler.
This issue often appears when the heating is first turned on after summer, as the circulation pump can seize up after long periods of inactivity.
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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