Error 321 - Hot Water NTC sensor Fault

What does 321 mean?

This error code indicates a problem with the Hot Water NTC (Negative Temperature Coefficient) sensor, which monitors the domestic hot water temperature. The boiler's display will show the spanner symbol and the numeric error code.

• Faulty Hot Water NTC sensor
• Damaged wiring to the sensor
• Loose sensor connection

Click steps to track your progress.

1. 1

   Press the 'R' (reset) button firmly for several seconds to attempt to clear the fault.

2. 2

   If the error persists, turn off the boiler's electrical supply at the isolation switch for 30 seconds, then turn it back on.

3. 3

   If the fault code reappears, contact your installer or the Baxi service division ('heateam') for assistance.