A20 error; heater may not start and shows low or zero pressure

Safety: Do not over-pressurize the system. Follow Beretta's specified pressure range.

• 1. Check mains water pressure: Open a cold tap and verify that flow is strong. If mains pressure is low, contact your water supplier.
• 2. For sealed systems: Check the pressure gauge on the heater. If below the minimum, use the filling loop to top up to the recommended pressure.
• 3. Inspect for leaks: Look around the heater and visible pipework for drips or stains indicating a leak.
• 4. Pressure sensor check (technician): If pressure is correct but A20 persists, the pressure sensor or switch may be faulty and require replacement.