Boiler does not ignite, burner does not start, display shows E01 shortly after a call for heat or hot water.

Safety first: Turn off the boiler with the main switch and close the gas cock before removing any covers. Wait for all hot surfaces to cool. If you ever smell gas, do not attempt repair—ventilate the room and call your gas supplier or a licensed technician immediately.

Step-by-step checks:

• 1. Reset the boiler: Use the front panel reset button (or power cycle for 30 seconds). If E01 returns immediately, continue with checks.
• 2. Check gas supply: Ensure the main gas cock to the Viadrus boiler is fully open. Confirm other gas appliances in the house work. If no gas, contact your gas supplier.
• 3. Inspect ignition electrode: Remove the front cover according to the Viadrus manual. Locate the ignition electrode near the burner. Check for cracked ceramic, loose connections, or heavy soot. Clean the tip gently with fine emery cloth and wipe with a dry cloth. Re-seat the electrode and ensure the cable is firmly connected to the ignition transformer.
• 4. Inspect ionisation (flame) electrode: Check that the ionisation electrode is correctly positioned in the burner flame path (usually 3–5 mm in the flame). Clean it as above and ensure the cable is not damaged or touching metal parts.
• 5. Check burner and injectors: Remove the burner assembly if accessible. Inspect burner ports and gas injectors for dust, rust flakes, or spider webs. Clean with a soft brush and compressed air (do not enlarge injector holes).
• 6. Verify gas valve operation: With power off, check the wiring harness to the gas valve for loose plugs or damaged insulation. With power on and a call for heat, you should hear a soft click from the gas valve. If there is no click and supply voltage is present at the valve terminals, the valve may be defective and must be replaced by a qualified technician.

When to stop: If E01 persists after cleaning electrodes and confirming gas supply, or if you are not trained to work on gas valves and combustion components, contact an authorised Viadrus service centre.