High
125 on Main Eco Compact System

Your boiler is failing to detect the expected rise in temperature after the burner fires up, indicating it cannot effectively transfer heat into your system.

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.

What the manual says

Manufacturer manual

primary water temperature has not changed by 1° C within 15-30 seconds of burner lighting, or if within 10 minutes of burner lighting, the primary water temperature has not changed

From this model's manual
Verified against the Main Eco Compact System installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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

E125View →E110View →

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