High Lockout
E317 on Potterton Promax HE

Your boiler has detected an issue with the electrical frequency of your home's power supply, meaning the electricity isn't entering the unit at the correct rate for it to operate.

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

Wrong power supply (HZ)

What causes this fault?

This fault occurs when the boiler's internal computer detects that the incoming electrical current does not match the standard 50Hz frequency required for UK appliances. The most common reason is a malfunctioning main PCB that can no longer accurately read the power supply, though it can occasionally be triggered by external issues like a faulty generator or a severe power surge.

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

E321View →E117View →E160View →

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