One thing we do know about the type of equipment we use, for them to work efficiently all the parts should be in working order. Oil burning furnaces and boilers are no different. We are entering into the time of the year where heating will be a critical part of our lives.


Regardless of what brand name furnace or boiler you have one of the most important parts is the nozzle. Not all nozzles are the same. Each manufacturer will have their own variations in their nozzles. This brings up the question of the correct nozzle. To help better understand what is the correct nozzle we will take a deeper look at the nozzle.


How does a nozzle work?


The nozzle is the part of the unit that will be used to spray the fuel of an oil burning furnace or boiler to fuel the flame. The energy is supplied to the nozzle at 100-150 PSIG (pounds force per square inch) for most residential applications and 300 PSIG in commercial applications. The nozzle converts energy from pressure to velocity. The viscosity of the fuel used can also effect the type of nozzle that need to be used. A smaller nozzle will pump pressure.


A nozzle is expected to deliver properly atomized fuel at a precise rate over a broad range of conditions. The fuel may be 40-50°F, the nozzle may operate at temperatures up to 250°F and the off cycle soak temperature may climb to nearly 300°F in some appliances. In spite of the adverse conditions, we expect the nozzle to deliver properly atomized fuel at the correct rate, pattern and angle.


We must help the nozzle do its job. First, make sure that the fuel supplied to it is clean. Make sure the pump pressure is set properly. For domestic applications it may be 100 PSIG to 150 PSIG. When installing the nozzle, use extreme care to protect the nozzle orifice and strainer. If the orifice gets dirt in it or becomes scratched, it will not function properly. Inspect the nozzle adapter before installing the nozzle. If there are deep grooves cut into it from previous nozzles, replace it. Those grooves or a scratched surface are a potential source for a leak. Do not over torque the nozzle when tightening. Over torqueing will cut grooves into the adapter and cause leaks when the next nozzle is installed.


When considering proper nozzle selection, remember these points:


  • Always use the appliance manufacturer’s nozzle specifications.
  • Follow the burner manufacturer’s recommendations when retrofitting a new burner to an old appliance.
  • You must set up the combustion with properly maintained test instruments. Smoke, CO2, or O2, drafts and pump pressure.


Nozzle sizing is an important factor when choosing the nozzle. If the correct nozzle is not chosen fuel will be wasted and you will not receive the peak performance from your furnace. There are a lot of charts that can be referenced over the internet. As with any type of major maintenance project it is better to leave it to the professionals. Contact your local

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