High
Casting Thermistor Fault on Potterton Suprima HE

Your boiler has lost the ability to accurately measure the temperature of its internal heat exchanger, so it has safely shut down 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

Automatic reset. Casting thermistor not giving valid readings or open/short circuit.

From this model's manual
Verified against the Potterton Suprima He System installation & service manual, page 25.
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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