BoilerFaultCodesTechnical description
Burner does not start. Safety limiter (limiter) has tripped. (Reset required: Turn control knob 'Reset' to the right until 'CL' appears, then turn back).
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 failed pump that isn't moving water effectively or a buildup of debris that has blocked the internal heat exchanger. It can also happen if there is a large amount of air trapped in the system or if the radiator valves are all closed at once.
This fault is more common in autumn when homeowners first turn their 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.