Oil burners & how they work

Updated February 21, 2017

Oil burners are appliances that heat the home using fuel oil instead of natural gas. While gas burners need a gas line to work, oil burners run off a refillable on-site oil reservoir. This makes them ideal for those living in remote locations without an installed gas line. Unfortunately, fuel oil is more expensive and more polluting than natural gas.

The Motor

An oil burner has an electric motor that turns a fan, drawing air into the blast tube. The motor also controls a pump that pulls heating oil out of a reservoir, through a filter and into a pressurised tube. The fan is usually activated by some sort of temperature sensor, such as a thermostat for air heaters or an aquastat for water heaters. When the temperature slips too low, the oil burner is automatically turned on.

The Blast Tube

The pressurised oil is sprayed into the blast tube in a fine mist by a nozzle. In the blast tube, it mixes with the air. Oil needs to be atomised into fine droplets to burn well, which is what the nozzle does. Inside the tube is the starter, a high-voltage gap between two wires. The voltage is so high that the hot electric spark that jumps between the two wires ignites the oil as it flows past.


The hot gas from the oil then flows upward to the heat exchanger. The heat exchanger is a thin wall of metal that separates the hot gas from the water or air that it needs to heat. The gasses heat the metal, which heats the water or air on the other side. The hot gas then continues upward out a chimney, where it is vented in the air.


There are two dangers posed by kerosene systems: fire and asphyxiation. If the kerosene does not light, it can continue to spray into the blast tube, potentially building up and later catching on fire, causing an out-of-control blaze. To prevent this, kerosene burners use a device called a CdS cell that detects light. The CdS cell is in the blast tube facing in the direction of the flame. If the CdS cell detects light after the lighter is turned on, it means the burner has ignited and everything is working properly. If the CdS cell does not detect light, however, it shuts off the burner automatically until someone comes along and resets it. Asphyxiation can occur if there is a gap in the exhaust pipe where combusted gasses leak into the house. It can also occur if something is blocking the chimney, preventing gas from escaping. The best way to safeguard against asphyxiation is to buy a carbon monoxide detector that will sound an alarm when dangerous amounts of the gas start to build up in the house.

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About the Author

Isaiah David is a freelance writer and musician living in Portland, Ore. He has over five years experience as a professional writer and has been published on various online outlets. He holds a degree in creative writing from the University of Michigan.