Oil boiler making noise — rumbling, banging, or vibrating
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Most likely cause & what to check
Oil boilers are inherently noisier than gas boilers due to the combustion process — a correctly functioning oil burner has a steady low roar when firing. Unusual noises — banging, vibrating, rattling, or a change in the combustion tone — indicate a problem.
A delayed ignition bang (a distinct thud or pop when the burner lights) indicates oil is accumulating in the combustion chamber before igniting. Causes: worn nozzle producing poor atomisation, low oil pressure, or a faulty photocell (the sensor that detects the flame). This fault should be investigated promptly — repeated delayed ignitions can crack the heat exchanger.
Vibration or rattling during operation often indicates a loose burner mounting, a worn burner fan bearing, or a flue pipe that is not properly supported. Check the burner is firmly bolted to the boiler and that the flue connections are tight.
A change in the combustion tone from steady to irregular, or a rhythmic pulsing, may indicate air in the oil supply — particularly if the tank was recently run dry or an oil delivery disturbed sediment at the bottom of the tank. The oil filter should be checked and the system bled.
Kettling (rumbling boiling sound from the boiler body, not the burner) is caused by scale or sludge on the heat exchanger — the same as in gas boilers. In oil systems this is less common but can occur in hard water areas.
Any new or unusual noise from an oil boiler warrants a call to an OFTEC engineer rather than a DIY investigation — the combustion components (nozzle, photocell, pump) are all service items and the safety implications of a poorly adjusted oil burner are significant.
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