BoilerFaultCodesTechnical description
Fault flow sensor over temperature – flow sensor flow/return line probe differential alarm
What causes this fault?
This fault occurs when the boiler's sensors detect that water is heating up far too quickly or staying too hot compared to the return flow. The most common reason is a circulation failure, often caused by a seized pump or a blockage in the heat exchanger that prevents water from moving through the system. It can also be triggered by a faulty sensor sending an incorrect temperature reading to the main control board.
This fault is more common in autumn when homeowners first turn their heating back on, as circulation pumps can often seize up after being idle during the summer months.
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.