Boiler shows E5 and stops, often during operation

Safety first: High flue temperature can be dangerous. Turn off the boiler and do not operate it if you suspect flue blockage. Only qualified engineers should work on the flue system.

• Check external flue terminal: From outside, ensure the Remeha concentric flue terminal is not blocked by leaves, plastic bags, snow, or bird nests.
• Check for signs of overheating: Listen for kettling noises and feel the casing (carefully) for excessive heat, which may indicate poor circulation.
• Engineer tasks: Inspect and clean the primary heat exchanger, verify correct flue configuration and length per Remeha installation manual, test the flue gas sensor, and replace it if readings are incorrect. Combustion must be checked with a flue gas analyser.