What does E40 mean?

The boiler's sensor for the central heating return temperature is faulty, either short-circuited or open-circuited.

• Faulty NTC (Negative Temperature Coefficient) sensor for central heating return.
• Loose or damaged wiring to the sensor.

Click steps to track your progress.

1. 1

   Turn off the main power supply to the boiler, wait 30 seconds, then turn it back on.

2. 2

   Check if the error code clears.

3. 3

   If the error persists, a qualified technician should check the return central heating NTC sensor and its wiring.