A1 warning, unit continues to operate but with reduced performance

Safety: Turn off power and close water and gas valves before removing any hydraulic components.

• Assess symptoms: Note if hot water temperature is unstable or recovery is slow. This often accompanies the A1 warning.
• Descale plate heat exchanger: Isolate the DHW plate heat exchanger using service valves. Remove and flush it with an approved descaling solution until flow and temperature response improve.
• Check primary side: Inspect the primary heat exchanger for visible scale or deposits. Professional chemical cleaning may be required.
• Install water treatment: In hard water areas, fit a water softener or scale inhibitor on the cold feed to the heater to prevent recurrence.
• Reset warning: After cleaning, clear the A1 warning via the control panel and monitor performance.