BoilerFaultCodesTechnical description
Water level low, Temperature rises too fast. Cause: Pump obstructed, pump running at lower capacity, Air in appliance, system pressure too low, flow and backflow NTC reversed
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the temperature is rising far too quickly, indicating that the heat isn't being carried away from the heat exchanger. The most common reason is a failing or stuck circulation pump, though it can also be triggered by a significant air lock or a blockage in the pipework preventing water flow. Essentially, the boiler is protecting itself from damage by shutting down because the water inside it is standing still and boiling.
This issue often surfaces in autumn when the heating is turned back on for the first time, as pumps can seize up after sitting idle 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.