Boiler indicates E15, safety chain open, burner cannot start.

Safety first: Disconnect power. Do not bypass safety devices.

• Check safety devices: Identify all safety devices in the chain (overheat thermostat, flue gas thermostat, gas pressure switches). Verify which one is open using a multimeter.
• Reset manual devices: If the overheat or flue gas thermostat has a manual reset button, press it once after the boiler has cooled and the cause has been addressed.
• Inspect gas pressure switches: Ensure gas supply is present and within the set range. If the switch does not close even with correct pressure, it may be faulty.
• Check wiring continuity: Inspect the safety loop wiring for loose connections or breaks. Repair or replace as needed.

When to call a professional: If a safety device repeatedly trips or if gas pressure switches need adjustment, contact an authorised technician.