BoilerFaultCodesTechnical description
Differential water flow switch fault (still open).
What causes this fault?
This fault occurs when the boiler's internal sensors detect that water isn't moving through the unit quickly enough to carry heat away safely. The most common reasons are a seized circulation pump, a blockage in the pipework, or a failure in the switch that monitors water flow. Because the heat cannot exit the boiler, the system shuts down to prevent the internal components from overheating.
This issue frequently appears during the first cold snap of autumn when a pump that has been idle all summer fails to restart or is hindered by settled debris.
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.
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