High
125 on Potterton Assure

Your boiler is struggling to move water around your heating system correctly, which is causing it to turn itself off to prevent overheating.

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

Poor primary circulation (if between 15 and 30 seconds of the burner lighting, the primary water temperature has not changed by 1° C OR if within 10 minutes of the burner lighting, the primary water temperature twice exceeds the selected temperature by 30°)

From this model's manual
Verified against the Potterton Assure 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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