Water heater does not ignite, burner does not light, display shows A01 shortly after a hot water demand.

Safety first: Turn the appliance OFF, close the gas isolation valve, and disconnect power before removing any covers. If you ever smell gas, ventilate the area and call a qualified gas technician immediately.

Step-by-step checks:

• 1. Verify gas supply: Ensure the external gas cock to the Ferroli water heater is fully open. Check that other gas appliances in the home work. If no gas anywhere, contact your gas supplier.
• 2. Reset the appliance: Use the reset button on the Ferroli control panel (refer to your model’s manual). If A01 clears and the unit ignites normally, monitor for recurrence.
• 3. Inspect ignition electrode: Remove the front cover (on most Ferroli models this requires undoing two screws at the bottom). Locate the ignition electrode near the burner. Check for cracks in the ceramic, heavy soot, or corrosion. Clean gently with fine emery cloth and ensure the tip is positioned correctly over the burner as per the service manual.
• 4. Check wiring to electrode and gas valve: Confirm the high-voltage lead to the electrode is firmly connected and not damaged. Inspect the gas valve connector for loose or burnt pins.
• 5. Professional tests: A qualified technician should measure gas inlet pressure, verify correct operation of the Ferroli gas valve, and test the main PCB ignition circuit. Replacement of the gas valve or PCB must be done by a licensed professional.

Do not repeatedly reset if A01 returns immediately; this can be unsafe. Have the unit inspected by a certified Ferroli service technician.