Boiler shows A07, burner stops and cannot restart until reset

Safety: Allow the boiler to cool down before touching any internal components. Do not bypass safety devices.

• Check system pressure: On the Hoval boiler display or gauge, ensure heating pressure is within the recommended range (typically 1.0–1.5 bar when cold). Top up via the filling loop if low, following the manual.
• Bleed radiators: Air in the system can cause local overheating. Bleed radiators and any high-point air vents, then recheck pressure.
• Verify pump operation: When there is a heat demand, feel the circulation pump body. It should vibrate slightly and get warm. If it is hot but not circulating, it may be seized or air-locked.
• Reset STB: Some Hoval boilers have a manual reset safety thermostat on the flow pipe or heat exchanger. After cooling, press the reset button if accessible as per the service manual.
• If the boiler repeatedly overheats, a technician should check for sludge in the primary heat exchanger, verify pump performance, and replace the STB if faulty.