Boiler shows C1 264, often related to low water pressure or circulation issues.

Safety first: Allow the system to cool before repressurising or bleeding radiators.

• Check pressure gauge: If below 1.0 bar, open the filling loop valves slowly until pressure reaches 1.2–1.5 bar, then close both valves fully.
• Bleed radiators: Starting from the lowest floor, bleed radiators to remove air. Top up pressure again afterwards.
• Check for leaks: Inspect visible pipework, radiators, and the boiler for signs of water leaks that could cause pressure loss.
• Engineer tasks: If the fault persists, an engineer should check pump operation, clean any system filter (e.g. Worcester Bosch Greenstar filter), and flush the system if heavily sludged.