Emergency Lockout
E21 on Potterton Powermax HE

Your boiler has detected that its electrical wires are connected the wrong way round at the power source, preventing it from starting up safely.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description

Live & Neutral supply reversed. Correct the electrical supply

What causes this fault?

This fault occurs when the electricity entering the boiler is wired incorrectly, with the live and neutral connections being swapped. This usually happens after electrical work has been carried out in the home or if a new fused power switch has been installed incorrectly. The boiler's safety sensors detect this 'reversed polarity' and prevent the system from firing to avoid an electrical hazard.

Engineer required

This is a emergency 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

E22View →

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