High Lockout
neon flashing on Potterton Performa System HE

Your boiler has detected an internal electrical or mechanical fault that is preventing it from circulating water around your home.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

The boiler has defaulted to a fault mode (Section B - Pump/PCB fault)

What causes this fault?

This fault occurs when the boiler's internal components fail to move water through the heat exchanger, causing the system to stall. The most common reason is a seized or failed circulation pump, though it can also be triggered by a communication error on the main control board that prevents power from reaching the pump.

This issue often surfaces at the start of autumn when a pump that has been idle all summer becomes seized with limescale or sludge upon 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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