How much does it cost to fix boiler error code E321?

Typical repair cost for the boiler E321 fault is £90-160 including labour.

E321 Medium

Boiler Fault Code E321

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code E321 appears across 3 boiler brands and 28 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected a problem with the sensor that monitors the temperature of your hot water, meaning your taps may not get as hot as they should or stay consistent. (As reported on Main Eco Compact)

Pick your boiler brand for the E321 fix

Baxi E321 24 models Main E321 2 models Potterton E321 2 models

Source

Information for the E321 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026