Boiler shows error 10, no heating or hot water, pump may run briefly then stop.

Safety: Allow the boiler to cool and isolate electrical power before opening the casing. Be prepared for water spillage when opening hydraulic components.

• Check system pressure: Ensure the pressure gauge reads within the recommended range (typically 1.0–1.5 bar when cold). If low, top up via the filling loop and bleed radiators.
• Bleed air: Bleed air from radiators and from the automatic air vent inside the boiler (if accessible). Air locks can prevent the flow sensor from detecting circulation.
• Inspect flow sensor/switch: Locate the flow sensor on the return or flow pipe inside the boiler. Check for debris or scale. On turbine-type sensors, remove and clean the turbine carefully. Replace the sensor if damaged.
• Check pump operation: During a heat demand, listen and feel for pump vibration. If the pump is silent or very hot and not circulating, it may be seized. Gently turn the pump shaft (if accessible) with a screwdriver to free it, or replace the pump if it does not run.
• Flush blocked circuits (engineer): If the primary heat exchanger or system is heavily sludged, a professional power flush or chemical clean may be required.
• Re-test: After restoring circulation, reset the boiler and confirm that error 10 clears and both heating and hot water operate normally.