BoilerFaultCodesAlpha 20 Fault Code
The Alpha 20 fault code means: your boiler is struggling to detect the flame needed to heat your water, even if the burner has successfully lit.. It appears on 26 Alpha models in our database.
Technical description: Flame sensing fault
What causes the Alpha 20 fault?
This fault occurs when the boiler's control system cannot confirm that a flame is present, even if the burner is actually firing. The most common reason is a buildup of carbon or debris on the monitoring probe, or a loose electrical connection that prevents the signal from reaching the main control board.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Alpha models that show the 20 fault code
Click a model for the full fault code list and model-specific repair notes.
- 240XE Repair: £150-300
- C25 Xtraflame Repair: £150-300
- CD Repair: £150-300
- E-Tec Repair: £150-300
- E-Tec 24 Repair: £150-300
- E-Tec 28 Repair: £150-300
- E-Tec 33 Repair: £150-300
- E-Tec Plus Repair: £150-300
- E-Tec Plus 10 / 18 Repair: £120-350
- E-Tec Plus 24 Repair: £150-300
- E-Tec Plus 28 Repair: £150-300
- E-Tec Plus 33 Repair: £150-300
- E-Tec R Repair: £150-250
- E-Tec Regular Repair: £90-250
- Eco Repair: £150-300
- Eco 11 13 Repair: £120-£350
- Evoke Repair: £150-300
- Evoke 10 / 18 Repair: £120-£250
- FMK Repair: £120-280
- H25 Xtraflame Repair: £150-300
- Intec 24GS Repair: £120-250
- Intec 28GS Repair: £150-300
- Intec 40GS2 Repair: £150-300
- Intec 50CS Repair: £150-300
- Intec2 25 28XE Repair: £120-250
- Intec2 30SE Repair: £150-300
Source
Alpha 20 fault code information on this page is sourced and cross-checked against the official Alpha service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026