BoilerFaultCodesAlpha 49 Fault Code
The Alpha 49 fault code means: your boiler has shut down because the water returning from your radiators has become too hot, usually caused by a circulation problem.. It appears on 7 Alpha models in our database.
Technical description: Return sensor high temperature intervention
What causes the Alpha 49 fault?
This fault occurs when the water coming back into the boiler from your heating system is much hotter than it should be, suggesting the heat isn't being distributed to your radiators. The most common reason is that the internal pump has failed or is struggling to push water through the pipes, causing heat to build up inside the unit. In some cases, a blockage in the system or a faulty temperature sensor can also trigger this safety shutdown.
This issue often surfaces during the first cold spell of autumn when the heating is turned on after being stagnant all summer, which can cause the pump to seize.
DIY fix possible
Check that at least two or three radiators have their valves turned fully openEnsure your central heating pump is running and hasn't seizedCheck the system pressure gauge and top up to 1.5 bar if it is low
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Gas Safe Register →Alpha models that show the 49 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Alpha 49 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