Parts of an Oil Burner


Oil burners perform relatively different forms from gas or biomass burners. This is why they have a slightly different design. For any fuel to be able to sustain a flame in a stable way, it needs to be in a gaseous state. Gas burners can do this directly as their fuel is in a suitable state. However, if the fuel is liquid (oil in our case), it must be aerated before it can sustain the flame. An oil burner’s gasification components are what makes it different from other burners. In this article, we will discuss the parts of an oil burner and how they differ from those of other burners. We will provide practical information that is both useful and educational.

General expanded view of an oil burner

As mentioned in the beginning, an oil burner has a different design from gas or biomass burners. All burners have been designed to allow the fuel to sustain a flame. Only when fuel is in a gaseous state is it able to burn in the specialized, controlled, and stable way that is required by the burner. If the source fuel is not gas, it must first be aerated.


Generally speaking, an oil burner differs from a gas burner in that it needs components that can convert liquid fuel into gas. It, therefore, needs parts that can handle liquid fuel in a safe way.

Oil burner design and parts can vary greatly from one brand to the next. This depends on whether it is an industrial or domestic burner, or whether it is a one-stage or two-stage burner. Included below is a general, expanded view of an oil burner.

We will not include every single component in this article and will focus rather on the most important ones and a few extra parts. We will group the components together according to function rather than the location in the burner. Sometimes, the same part can belong to more than one group, but we will include it in only one group.

Electric circuit

An oil burner’s electric circuit consists of the control box or switchboard, the photocell, the transformer, the motor, the coil, the solenoid valve, and accessories such as the condenser.

  • Switchboard: The switchboard is also known as the control box or control module. Its name gives a good indication of its function. The control unit acts as a sort of central nervous system from which all the important functions of the boiler are controlled electronically. It consists of a system of electrical ports (terminals) in the base that can be connected to a large number of cables that communicate with various other boiler parts (for example, the photocell, thermostat, resistors, motors, transformers, coils, safety systems, signals, etc). The control unit can normally accommodate a set number of cables and connections according to the boiler’s needs. It typically has sketches or diagrams specifying which electronic parts can be connected to it and where.
  • Photocell: The photocell is both an electronic and photosensitive part. It is located very close to the place where the burner flame is emitted. Its function is to detect the presence of a flame and it works closely with the control unit to manage the burner’s on and off sequences. This depends on the hot water needed to maintain the set temperature in the house.
  • Transformer: Its function is to increase the voltage so that the burner can operate to its full capacity. It is responsible for sending enough current to the electrodes so that they can form a high voltage electric arc between the two terminals and ignite the already-atomized fuel.
  • Motor: This is an electrical device that consists of what is known as a joint shaft that moves the pump and burner turbine simultaneously, and is located between the pump and the turbine. It is one of the parts that is connected to the switchboard. This part needs to be attached to the capacitor, which is another component whose main function is to store energy for the motor when it starts up and during operation.
  • Coil: The coil is working closely with the pump and motor. It plays an essential role in starting up the process and provides the peak voltage that is required to start the motor.
  • Solenoid valve: Depending on the boiler’s design and brand, the burner may have one or more solenoid valves. A solenoid valve is a solenoid device that functions as a valve and has a stable magnetic field. This special magnetic field allows this part to ensure that the fuel going into the burner nozzle is in a stable state.

Fuel circuit

The fuel circuit is a system of components through which the oil circulates after it is taken up by the pump. After this, it is atomized in the jet or spray nozzle.

  • Hoses: These are small, flexible connecting pipes. They have fittings in the tips and lead the fuel to the pump. Although hoses are seemingly unimportant, they should not be overlooked. When boilers have what appear to be major breakdowns, very often this is due to congested, twisted, or blocked hoses or holes in the hoses, resulting in air incorporation. This also causes the hoses to be less effective in allowing the diesel oil into the pump to remove the excess. When installing your boiler, you should avoid twisting the hoses as much as possible because, in the long term, this will almost certainly cause problems.
  • Pump: The pump’s function is to suck in the fuel from the tank and into the tank with enough pressure to achieve atomization, which occurs at the nozzle. The fuel pump compresses the diesel oil so that it is at the right pressure for atomization at the nozzle outlet. Another one of its functions is to return any excess diesel oil.
  • Spray nozzle: Also known as the injector or jet (a word that comes from the French word “gicleur”), the spray nozzle (as its name implies) is responsible for spraying or atomizing the liquid fuel, an essential step to allow it to burn and sustain a stable flame. The spray nozzle works by placing the fuel under high pressure and then dorcing it out of a small hole while it is being propelled by the fuel pump. The spray nozzle is not a universal part and not all nozzles can be used with any burner or boiler. Your choice of the nozzle should be based on: the design of your boiler’s burner, the unit’s thermal power, and the kind of fuel it uses.
  • Flame tube (burner barrel): The flame tube contains the main parts that carry out combustion. In this important part, the deflector and the electrodes are found. The flame outlet or nozzle is located at the end of the flame tube. The photocell is situated at the flame tube’s inlet. The flame tube plays a fundamental role in the fuel vaporization process and the stabilization of the flame. This is where the fuel output is regulated and also where the air coming from the turbine is regulated by the clapper.
  • Deflector: This is also known as the stabilizer. This part is located at the end of the burner barrel and its function is to treat the air passing through the slots to form the necessary vacuum to stabilize the flame and create the ideal temperature for fuel atomization.
  • Preheater: This part is designed to heat the air just before the combustion process. It helps to achieve better thermal performance. When it functions optimally, the preheater reduces heat loss (that would take place through the exhaust gases) by up to 10%. It, therefore, helps with fuel efficiency and helps reduce polluting emissions.
  • Electrodes: The electrodes are rods that are normally made from stainless steel and covered almost entirely with ceramic material as an electrical insulator (there is less on the tips). This insulation is important because electrodes work with the high voltage that the ignition transformer transmits through them. This generates an electric arc that is able to ignite the fuel sprayed by the injector nozzle, resulting in combustion in the burner. The electrodes’ two tips should be positioned slightly in front of the spray tip and at the distance recommended in the user manual.

Ventilation and gas expulsion

  • Turbine: This is sometimes simply referred to as the fan. It is a part that has a cylindrical design that is responsible for bringing fresh air into the burner, ventilating, and extracting hot air from the burner. It does this in either a clockwise or counterclockwise direction. The turbine must be in exact alignment with the internal plate, otherwise, it cannot perform its function properly.
  • Servomotor: This component can be part of either analog or digital technology and always has a highly specialized and automatic design. Its function is to regulate and distribute the airflow in the burner. It does this in various positions, depending on how many flames the burner has.
  • Clapper. The clapper is an electronically controlled device that manages and regulates air intake from the turbine to the combustion area. By adjusting the flap appropriately (the more open = the more air, the more closed = less air), the amount of air can be regulated according to how much air the fuel needs. The clapper plays a vital role in fuel efficiency and minimizing polluting emissions. When the burner is not operating and doesn’t have a flame, the clapper closes automatically to prevent air emission to cool the combustion chamber.

Obtain oil burners and accessories from Suner

If you are looking to replace your boiler’s oil burner, Suner is your best bet. We have an extensive catalog of prestigious brand oil burners in our store. Our catalog also includes extensive accessories for oil burners. You will always find what you’re looking for with us. Click on one of the below links to find oil burners and accessories:

Remember that in addition to our high-quality products, we also have many satisfied customers throughout the world, and offer the customer service and aftersales service that you need. Our deliveries are fast and efficient as we value our customers.

If you are interested, you can also download and install the Suner app, which will allow you to have access to all our offers on your mobile device. Check out this instructional video on our YouTube channel for more details.

Maintenance tips for burner parts

Burners need regular maintenance, which should be done at least once a year by a qualified technician who is familiar with international and local regulations.


Regular maintenance helps keep all the burner’s components working as they should so that they don’t break down or require replacement. It also ensures that fuel efficiency is optimal and that no unburned fuel exits the chimney, thereby minimizing polluting gas emissions.

  • The first step for burner part maintenance is to carry out an important safety measure: before doing any maintenance on a boiler (especially on the burner), the unit should be completely switched off and unplugged. You might also want to turn off your home’s general power supply.
  • Check that there are no kinks, seals, twists, clogs, holes, or changes of any kind in the fuel supply and return pipes, especially in the hoses. Very often, a burner can become blocked or stop working due to seemingly serious reasons. However, in reality, it is because the fuel is not reaching it at the correct flow rate or not at all. The hoses are delicate and fragile parts and, if they get damaged, it’s best to replace rather than repair them.
  • Start by cleaning the filter in the fuel intake duct and pump filter very well. Always remember that the filter is a very important component and is similar to the hoses (as mentioned in the previous point) and can experience the same minor problems, which can become major problems.
  • The photoresistor contains an electronic board that is continuously exposed to the burner flame. It’s not uncommon for it to get dirty or to break down. To find out if it is dirty or damaged, you can perform a few technical checks. If you find that it is only dirty, simply wipe it down with a dry cloth. If it is damaged, replace it with a new part. Use this link for photoresistor spare parts for sale at Suner. For more information on how to check, clean or replace a photoresistor, read this article that we have compiled.
  • Check your burner’s nozzle and ensure that it is the correct part. If the nozzle doesn’t comply with your boiler’s required power, fuel flow, heating, or your home’s DHW needs, the burner won’t be able to work optimally and will use too much fuel. It will also pollute the environment and your energy bill will be higher.
  • Check that the electrodes are correctly positioned and at the right distance from both terminals and from the nozzle. Your burner relies on this part to start up properly and to continue working optimally. This part also cleans the combustion head in the fuel outlet area, which is on the flame stabilizer.
  • After carrying out all of the above-mentioned burner part maintenance tips, start your boiler up again so that it runs at full power for about 10 minutes. This will allow you to check if everything is working as it should.

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