What does the Worcester Bosch E9 221 fault code mean?

Your boiler has detected that a critical safety sensor is disconnected or faulty, so it has safely shut itself down to prevent overheating.

How much does it cost to fix Worcester Bosch error code E9 221?

Typical repair cost for the Worcester Bosch E9 221 fault is £150-250 including labour.

Safety sensor open circuit - Maximum temperature sensor on the main heat exchanger has not been recognised.

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Work through these before the call-out.

Lockout fault with a reset-needed pattern.

Safety-critical — turn off, read this.