Your boiler is struggling to control how much water flows through the system, which can prevent it from heating up correctly.

The flow limiter is not properly adjusted.

What causes this fault?

This fault occurs when the boiler's internal sensors detect that water is moving through the system at an incorrect speed, usually triggered by an improperly set flow regulator. The most common reason is that the mechanical limiter has shifted out of its calibrated position or has become blocked by internal debris, preventing the boiler from managing heat transfer safely. It can also be caused by a sensor failing to accurately report the water speed to the main control board.