Oil burners are devices that use oil as fuel to produce heat for various applications, such as furnaces, boilers, water heaters, and ovens. Oil burners consist of several components, such as a fuel pump, a nozzle, an ignition transformer, electrodes, a combustion chamber, and a blower. When the oil burner is activated, the fuel pump draws oil from the storage tank and delivers it to the nozzle, where it is atomized into fine droplets. The ignition transformer generates a high voltage that creates an electric arc between the electrodes, which ignites the oil spray. The combustion chamber contains the flame and transfers the heat to the appliance. The blower provides the necessary air for combustion and ventilation.
However, sometimes the oil burner may not ignite properly, resulting in a delayed ignition. Delayed ignition is a condition where the oil spray accumulates in the combustion chamber before it is ignited, causing a loud bang or puff-back when the flame finally catches. Delayed ignition can damage the oil burner, the appliance, and the surrounding area, as well as pose a fire and safety hazard. Therefore, it is important to identify the causes of delayed ignition and apply the appropriate solutions.
Causes of Delayed Ignition
There are many possible factors that can cause delayed ignition in oil burners, but they can be broadly classified into three categories: electrical, air, and oil. The following table summarizes some of the common causes and their effects on the ignition system.
| Category | Cause | Effect |
|---|---|---|
| Electrical | Low supply voltage | Reduces the output voltage of the ignition transformer, resulting in a weak ignition arc |
| Electrical | Faulty relay contacts | Interrupts the power supply to the ignition transformer or the motor |
| Electrical | Defective ignition transformer | Fails to generate the required high voltage for the electrodes |
| Electrical | Damaged electrodes or porcelain bushings | Prevents the formation of a stable and intense arc |
| Electrical | Improper electrode gap or alignment | Affects the position and shape of the arc |
| Air | Excessive or insufficient combustion air | Creates an unbalanced air-fuel ratio, resulting in poor flame retention and mixing |
| Air | Clogged or damaged combustion head | Restricts the air flow and distribution to the nozzle |
| Air | Cold combustion air | Lowers the temperature of the oil droplets, increasing the energy required for vaporization and ignition |
| Air | High or low draft | Alters the pressure and velocity of the air in the combustion chamber |
| Oil | Clogged or defective nozzle | Affects the spray pattern and quality of the oil droplets |
| Oil | Air leaks in the suction line | Introduces air bubbles into the oil, disrupting the atomization and ignition |
| Oil | Oil line restriction or clogged oil filter | Reduces the oil pressure and flow to the nozzle |
| Oil | Wrong nozzle size or type | Exceeds or falls below the specified range of the combustion head |
Solutions for Delayed Ignition
To prevent or fix delayed ignition problems, the oil burner should be inspected and maintained regularly by a qualified technician. The following are some of the possible solutions for each category of causes.
- Electrical: Check the supply voltage and the input and output of the ignition transformer with a voltmeter. Replace the faulty relay contacts, the defective ignition transformer, or the damaged electrodes or porcelain bushings. Adjust the electrode gap and alignment according to the manufacturer’s specifications.
- Air: Measure the over-fire draft and the smoke level with a manometer and a smoke tester. Adjust the combustion air until a trace of smoke is achieved with zero to negative over-fire draft. Install a barometric damper or a draft inducer if the draft is too high or too low. Clean the combustion head and remove any foreign matter. Use warm combustion air if possible.
- Oil: Replace the clogged or defective nozzle with the correct size and type. Check the suction line for air leaks and seal them. Clean or replace the oil filter. Ensure the oil pressure and flow are adequate and consistent.
