BoilerFaultCodesTechnical description
Water shortage (Temperature difference between flow and return NTC is too large)
What causes this fault?
This fault occurs when the boiler's internal sensors detect that water is heating up too quickly or isn't circulating fast enough to carry heat away. The most common reasons are a seized or failing pump, a blockage in the pipework, or air trapped within the heat exchanger. Essentially, the boiler shuts down to prevent itself from overheating because the hot water hasn't moved out of the unit.
This fault is more common in autumn when heating systems are switched on after a long summer break, as circulation pumps can often seize up from lack of use.
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.