High Lockout
F34 on Ferroli BlueHelix Pro 32C

Your boiler has stopped working because the electrical power supply coming into your home is currently too low for the system to operate safely.

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

Supply voltage under 170V

What causes this fault?

This fault occurs when the electrical supply entering the boiler drops to a level that is too weak to power the internal components safely. The most common reason is an external issue with the local power grid, but it can also be triggered by a faulty control board inside the boiler that is misreading the incoming voltage.

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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Related fault codes

F37View →

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