BoilerFaultCodesTechnical description
Cycle time (hot water - combi only)
What causes this fault?
This fault occurs when the boiler detects that it is heating up too quickly or reaching high temperatures before it can transfer that heat to your running tap. This is usually caused by a buildup of limescale or debris inside the internal plates, which restricts the flow of water and forces the boiler to shut down to prevent damage. Essentially, the boiler is generating heat but has nowhere for it to go, leading to a constant cycle of starting and stopping.
This issue is often more noticeable in winter when users increase the demand for hot water and the temperature difference between incoming cold water and the desired output is at its highest.
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.