BoilerFaultCodesTechnical description
Maximum delta temperature
What causes this fault?
This fault occurs when the internal sensors detect that water inside the boiler is getting too hot too quickly, or there is too large a temperature difference between the water leaving and returning to the unit. The most common reason is a lack of water flow, often caused by a failing pump or a blockage in the pipework that prevents heat from being carried away to your radiators. It can also be triggered if the sensors themselves become faulty and provide inaccurate temperature readings to the control board.
This fault is frequently seen at the start of autumn when heating systems are turned back on after a long summer break, which can cause internal pump components to seize.
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.