High Lockout
661 on Worcester Bosch WR325 RSF

Your boiler is not receiving the correct electrical voltage needed to run, likely due to an issue with your home's power supply or a failing internal circuit board.

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

Unsatisfactory condition - power supply

What causes this fault?

This fault occurs when the boiler's internal electronic brain detects that the incoming electricity is at the wrong voltage or frequency to operate safely. The most common reason is a failing Printed Circuit Board (PCB) that can no longer process power correctly, though it can also be triggered by external issues like a faulty main power supply or loose electrical connections.

This fault is slightly more common during winter or stormy weather, when local power surges or grid fluctuations are more likely to interfere with sensitive boiler electronics.

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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