Boiler shows E28, often associated with condensate issues or blocked trap

Safety first: Isolate power. Condensate is mildly acidic; wear gloves and eye protection when handling.

User checks:

• Inspect the external condensate pipe for freezing in cold weather; thaw gently with warm water and lag the pipe.

Engineer checks:

• Remove and clean the condensate trap; flush with clean water and ensure it is refilled before refitting.
• Check the condensate pipework for correct fall and absence of sags or blockages.
• Verify that the trap seals correctly and no air is being drawn through.

Once the condensate path is clear and the trap is refilled, reset the boiler and test operation.