Boiler displays E20; safety cut-out triggered due to internal leak or moisture

Safety first: Immediately switch off power and close isolation valves to prevent further leakage. Do not operate the boiler with suspected internal leaks.

Steps to check:

• Inspect inside casing: Remove the front cover and look for visible water, corrosion tracks, or damp insulation.
• Identify leak source: Check around the heat exchanger, pump unions, safety valve, automatic air vent, and DHW connections for drips or staining.
• Dry components: Carefully dry any wet areas with absorbent cloths. Do not use the boiler until the leak is repaired.
• Check leak sensor: Locate the leak detection sensor (often at the base of the boiler). Ensure it is clean and properly positioned.
• Repair leaks: Tighten or replace leaking fittings, O-rings, or components as needed.

When to call a technician: Internal leaks near electrical components or the heat exchanger should be addressed by a qualified technician.