BoilerFaultCodesAlpha 45 Fault Code
The Alpha 45 fault code means: your boiler is overheating because the water is not flowing through the system as quickly as it should.. It appears on 20 Alpha models in our database.
Technical description: High-temperature difference
What causes the Alpha 45 fault?
This fault occurs when the water inside the boiler heats up too quickly because it isn't being moved away into your radiators fast enough. The most common reasons are a failing external pump, a blockage in the pipework, or a buildup of debris and limescale inside the heat exchanger that restricts water flow.
This issue often surfaces in autumn when the heating is turned back on after a long summer break, as external pumps can seize up during periods of inactivity.
DIY fix possible
Check that all radiator valves (TRVs) are fully openEnsure the external system pump is running and hasn't seizedCheck for any blockages in the system filters
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Alpha models that show the 45 fault code
Click a model for the full fault code list and model-specific repair notes.
- C25 Xtraflame Repair: £150-350
- E-Tec Repair: £150-350
- E-Tec 24 Repair: £150-350
- E-Tec 28 Repair: £150-350
- E-Tec 33 Repair: £150-350
- 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: £120-250
- E-Tec Regular Repair: £120-£350
- Evoke Repair: £150-300
- Evoke 10 / 18 Repair: £120-£350
- FMK Repair: £120-350
- H25 Xtraflame Repair: £150-350
- Intec 28GS Repair: £150-350
- Intec 50CS Repair: £150-350
- Intec2 25 28XE Repair: £150-250
- Intec2 30SE Repair: £150-300
Source
Alpha 45 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