BoilerFaultCodesTechnical description
Primary flow temperature rising too fast
What causes this fault?
This fault occurs when the water inside the boiler heats up much faster than the system can pump it away. It is usually caused by a failing pump that isn't pushing water effectively or a internal blockage, such as sludge or limescale, that is restricting the flow. When the sensors detect this rapid heat spike, the boiler shuts down to prevent internal damage or melting.
This issue often surfaces during the first cold snap of autumn when a pump that has been idle all summer has seized or 'stuck' and cannot restart.
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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