BoilerFaultCodesTechnical description
The diagnostics will indicate the nature of the fault to assist a speedy and effective repair
What causes this fault?
This fault occurs when the boiler's internal sensors detect that water is not moving through the heat exchanger at the required rate, often due to a mechanical failure or a blockage. The most common reason is a seized or worn-out circulation pump, though it can also be caused by air trapped in the system or a build-up of sludge obstructing the flow. Without this movement, the boiler must shut down to prevent the unit from overheating and causing internal damage.
This issue is frequently seen at the start of autumn when heating systems are switched back on after being idle all summer, which can cause the 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.