Oil boiler annual service — what does it include?
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Most likely cause & what to check
The engineer should start with a visual inspection of the boiler, burner, flue system, and oil line. They check for any obvious leaks, damage, or unsafe conditions.
The burner is cleaned: nozzle replaced, electrodes cleaned or replaced, air shutter and fuel pump pressure set to manufacturer's specifications.
The oil filter (usually on the fire valve or burner) is replaced. A blocked filter is a very common cause of lockout and poor combustion.
Combustion is tested with an analyser: flue gas temperature, CO2 percentage, and smoke number are checked against specification. Poor combustion means poor efficiency and potential CO production.
The heat exchanger is cleaned of soot deposits, which act as an insulator and reduce efficiency significantly.
The flue system is inspected inside and out — blocked flues are a major CO risk. The terminal is checked for debris and the flue integrity is confirmed.
The engineer should leave you with a service report showing all readings and any parts replaced. Keep this alongside your boiler warranty documents.
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