BoilerFaultCodesTechnical description
Thermostat operated safety
What causes this fault?
This fault occurs when the water inside the boiler gets too hot, triggering a safety switch to shut the system down. The most common reasons are a pump failure preventing water from moving through the unit, or a internal blockage like air or sludge that is trapping heat in the heat exchanger.
This issue often appears when you first turn the heating back on in autumn, as circulation pumps can seize up if they have been 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.
Find a Gas Safe engineer
Search the official register →