How to Build a Waste Oil Burner

A waste oil burner runs on used vegetable oil.

With heating oil prices as high as they are, you may be interested in building an experimental waste oil burner for a furnace, heater or boiler. This article walks you through converting a standard Beckett AFG oil burner to run on waste motor oil, used automatic transmission fluid (ATF), fryer grease or waste vegetable oil.

Things You'll Need

• Oil burner "gun," such as the Beckett AFG oil burner
• Furnace or boiler
• Siphon nozzle
• Air compressor
• Preheater
• Temperature controller
• Solenoid valves
• Constant-level tank
• Turbine-style retention head

Instructions

1. Obtain a Beckett AFG or similar oil burner "gun" to experiment with. They can often be found secondhand or in scrap yards. Remove the high-pressure fuel pump and cover the opening.

2. Purchase an air-atomizing "siphon" nozzle, such as a Delavan or Hago siphon nozzle. A 0.5-gallon-per-hour model is a good place to start. Waste oil fuel is difficult to atomize using a conventional pressure nozzle, and a siphon nozzle, which works very much like an airbrush or paint spray gun that uses compressed air, doesn't clog as easily. If you are using the manufacturer's supplied adapter to hold the nozzle, be aware that the air goes in the threaded port on the end opposite the nozzle and the fuel is fed through the port in the side.

3. Build a preheater. Waste oil has a higher viscosity and is harder to ignite than standard home heating oil, so preheating the fuel and air to somewhere between 150 and 350 degrees Fahrenheit is required. Because the fuel flows quite slowly through the lines, the fuel must be preheated to its final temperature at or very close to the nozzle. One way to do this is with an aluminum block machined to accept the siphon nozzle on one end. Drill fuel and air passages in the block as well as some holes to accept cartridge heaters. You could also build an external preheater and route the fuel line directly through a hole in the blast tube.

4. Connect a compressed-air supply. If you already own an air compressor, this is the simplest solution. The air supply should be routed to an adjustable regulator where the pressure is maintained somewhere in the range of 10 to 15 psi. The air flow is turned on and off by a solenoid valve wired in parallel with the burner motor and ignition.

5. Arrange for a constant low-pressure fuel feed. This can be done with a small tank and a float-controlled valve that keeps the fuel at a constant height. The fuel level can be located above or below the nozzle, depending on the flow rate you wish to achieve. If the fuel level is above the nozzle, use a solenoid valve to prevent the fuel from flowing when the burner is off.

6. Connect the temperature controller. It is best to have the preheater off when the burner is not running, but the preheater must be up to temperature before the burner attempts to start. If you use a digital PID temperature controller that has an alarm output, you can do this easily.

7. Use the furnace or boiler's limit control to the turn on the temperature controller when the thermostat calls for heat. Set the temperature controller's alarm output to turn on when the preheater nears the set-point temperature. Use the alarm output to power the burner's fan motor, ignition and solenoids.

8. Install a turbine-style retention head. The waste oil flame generated by the siphon nozzle tends to be longer than the standard-pressure nozzle flame. If the flame touches the back of the firebox, a special retention head may help.

Tips & Warnings

• This is an experiment burner that is not intended for normal use in a building. Doing so may void your insurance and/or violate building codes!

• Do not tamper with or remove the cad cell flame sensor and oil primary safety device.

References

• THS Engineering; Waste Oil Furnace Secrets; Tom Scarince; March 2009