BoilerFaultCodesAlpha 0A37 – Pro Tec 50 Fault Code
Also written as 0A37PROTEC50 — same fault.
The Alpha 0A37 – Pro Tec 50 fault code means: your boiler has stopped working because water is not moving through the heating system quickly enough to prevent the unit from overheating.. It appears on 2 Alpha models in our database.
Technical description: Insufficient system flow (if the system flow is too low for a certain length of time boiler will switch off)
What causes the Alpha 0A37 – Pro Tec 50 fault?
This fault occurs when the water inside the boiler heats up too quickly because it is not being pumped away through your radiators effectively. The most common reasons are a failed internal pump, a build-up of sludge blocking the pipework, or air trapped within the heating system preventing smooth circulation.
This issue often comes to light during the autumn when the heating is turned back on for the first time after summer, as pump components can seize during long periods of inactivity.
DIY fix possible
Check that all radiator valves and any external isolation valves are fully openEnsure your system pressure is at the correct level, usually between 1.0 and 1.5 barBleed all radiators to remove trapped air that might be blocking flow
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Gas Safe Register →Alpha models that show the 0A37 – Pro Tec 50 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Alpha 0A37 – Pro Tec 50 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