High Lockout
E85802 on Potterton Powermax HE

Your boiler has suffered an electrical failure where an internal fuse has blown, meaning the system cannot power its main components to provide heat or hot water.

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

Fuse 3.15A “Slow Blow”

What causes this fault?

This fault occurs when an electrical surge or a component failure causes the boiler's internal safety fuse to blow, cutting off power to prevent further damage. The most common reason for this is an aging internal pump that has seized or short-circuited, drawing too much current and overloading the system's delicate electronics.

This issue is more frequent at the start of autumn, as pumps that have sat idle during the summer are more likely to seize or fail when first switched back on for heating.

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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