Most homes that are situated in the more colder climates of the US are outfitted with oil fired furnaces or boilers that run on #2 heating oil (almost the same as diesel fuel but without the additive package).
In the heart of these heating systems is the oil burner. This is the actual mechanism that burns the fuel to create the heat source, or the flame. If this device does not work the rest of the equipment will not work either. This is why I think it is important for every homeowner to know exactly how oil burners operate so that if they fail you have a general idea of how diagnose and fix them (either by yourself or by a certified heating technician).
The Process of How Oil Burners Run A Furnace or Boiler
1. There is a device called an aquastat that triggers the power. When this happens the electric power to the heating system you have is turned on. The electricity that goes to your burners or boiler is controlled by a safety control called a Cad Cell relay.
2. Once the electricity is turned on the heart of your heating system, the oil burner, commences its operation. When it starts to receive electricity the electric motor within the system causes a shaft to rotate.
3. Then the shaft under oil burner starts to rotate. Without going into detail this starts the air blower and oil pump.
4. As the fan on your oil burner is spinning it is drawing air through the intake system slots. This air will be used for the combustion process. The heating oil has to be mixed with air to ignite properly.
5. At the same time as the fan is drawing air the motor shaft, which runs off of electricity, is driving the oil pump.
What does the oil pump do? This device is drawing fuel (the heating oil) from your tank.
Fuel lines are connected from your holding tank to your oil burner and the oil pump draws it out. If your system is set up right the fuel will pass through a oil filter and an internal screen of some sort to get out any more moisture or sediments. As the fuel is coming up it is highly pressurized.
This pressurized fuel, which can be over 100 psi, goes from your holding (storage) tank, through the pump, into your oil burner. As it flows through your oil burner it is turned into a very fine mist, or spray, as it flows through an oil nozzle that is attached to be in a the oil burner mechanism.
So here’s what we have so far. The fan blower is bringing in air and the pump is bringing in fuel. Two out of the three components we need for combustion. The last thing that is required is the spark to light it all.
6. The device that sparks the air in fuel on an oil burner is called the ignition transformer. You can spot this thing really easy as it is going to be a black box that is situated at the very top of the whole device.
The ignition transformer receives electricity and then converts it to a very high voltage which is then transferred to dual electrodes that is located at the end of the oil burner nozzle.
These electrodes are separated by a very small space, or gap, and and produces spark to ignite the fuel and air as it is being sprayed out of the nozzle.
There are systems in place (Cad Cell Relay, Stack Relay Switch, Flame Sensor) that will turn off any burner if there is not a flame produced. You not want your system to continuously pump heating oil out of your nozzle if it is not being used. This would be extremely dangerous!
7. So the fuel and air, coming out of the nozzle, are being ignited to produce a huge flame. This flame heats the rest of the heating system.
If you have a boiler the flame is heating the combustion chamber which in turn is heating the water which flows throughout the building. If you have a furnace the flame is heating that and that hot air is then blown throughout a room.
The combustion chamber liner prevents the oil burner from damaging the cast iron or steel boiler itself, while the hot surface of the combustion chamber liner helps make sure that all of the fine droplets of oil sprayed into the combustion chamber do in fact ignite.
9. When you’re aquastat (or thermostat) has sensed that the right temperature in a house or building has been reached it turns all the power to be oil burner off.
If you think your oil burner is failing to come on when it should or failing to go off after structure is already heated and this is the device that may be malfunctioning. Before all those other systems go on the aquastat have to tell it to. Many times this is the first device a heating technician will check.
Quick Recap of How Oil Burners Work (Summary)
These heating systems work by turning heating oil, a combustible substance, into heat.
It is pulled from your storage tank by the oil pump first.
It is pressurized and turned into vapor which then passes through your a burner’s nozzle as a very fine mist.
The mist that comes out of the nozzle is mixed with air and ignited by electrodes.
A flame is produced from this process which causes a combustion chamber or the air around it to be heated up.
And this is how many of our homes are heated. You want to make sure you get your oil burner serviced on the recommended maintenance schedules.
There is nothing worse than having your boiler or furnace break down in the middle of winter. Even if it is not winter you can find yourself taking cold showers if this device fails in any way. Hopefully by being more familiar with how it works you can backtrack and try to troubleshoot some things.