BoilerFaultCodesTechnical description
Overheat thermostat safety tripped
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature, triggering a safety switch to prevent damage. The most common reason is that the water isn't moving through the system quickly enough, often due to a failed pump, a blockage of sludge, or air trapped inside the heat exchanger.
This fault is more common when you first turn the heating back on after summer, as pump components can seize during 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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