MX-Series Preheater Clog Test

Lanair Products, LLC

  • Preheater Clog/Flow Test

Lanair MX-Series Preheater Clog Test

In this video we will discuss how to test for a clogged preheater assembly on a Lanair MX-series waste-oil heater. We’ll cover troubleshooting the burner fuel flow and confirm that fuel is reaching the combustion chamber.

If your heating unit will power up and attempt to operate, but will not spray fuel from the nozzle, this video should help.

It’s important to follow safety guidelines when working on mechanical, plumbing, and electrical equipment. Only allow qualified technicians to work on your system and ensure that the appropriate personal protective equipment and safe practices are used throughout the work.

Tools and equipment:
  • A face shield or safety goggles should be worn at all times when or working closely with a unit that is in operation.
  • Insulated gloves to protect against both heat and electrical shock
  • A flashlight
  • 13/16-ths (thirteen sixteenths) crescent wrench
  • 9/16-ths (nine sixteenths) socket wrench
  • 1/2 (one half) inch wrench
  • A Phillips-head screwdriver
Step One

An important step in preparing to test the burner fuel flow of a Lanair heater is to remove the compressed-air supply to the burner. This will prevent accidental ignition of fuel during testing. Be sure to leave the compressed-air supply disconnected from the burner throughout the testing process.

To remove the compressed-air supply from the burner, first set the secondary air-pressure regulator to 0 (zero) psi. Then, use the half-inch wrench to remove the air line from the burner.

Using the Phillips-head screwdriver, remove the large Phillips-head screw securing the burner cover closed.

Step Two

Begin to open the burner lid by pulling it towards you along the slotted hinge. Lift the lid to a 90 (ninety) degree angle, then let it slide downward to remain fixed in the open position.

Step Three

Locate the preheater assembly within the burner. With a gloved hand, turn the diaphragm-adjustment knob, at the rear of the preheater assembly, for 2 (two) full rotations in the counter-clockwise direction to allow fuel to flow through the burner in the absence of compressed air.

Step Four

Close the burner lid and resecure it with the screw.

Step Five

Establish a call for heat to the unit by setting the thermostat to its maximum temperature setting. If the red light on the burner’s primary control is indicating that the unit is locked out, you will need to press the reset button on the top of primary control to reset the burner. The unit should now attempt to start operating.

Step Six

Ensure that the oil-pressure gauge is reading an appropriate value before continuing with this test. Consult the product manual for confirmation.

Step Seven

While the burner is attempting to start, use a gloved hand to open the viewport on the furnace cabinet.

Step Eight

Use the flashlight to illuminate the rear wall of the combustion chamber through the viewport. If the preheater is clean and fuel is flowing, a steady spattering of fuel should be streaming across the combustion chamber, hitting the insulation on the rear wall.

The burner’s primary control will interrupt the startup sequence after a set period of time, due to lack of flame. If this occurs, reset the primary control and continue testing, but be sure that unburned fuel is not flowing into the combustion chamber

Additional Troubleshooting

If this process takes more than a few attempts, you may need to hold the reset button down for a longer period, in order to unlock the primary control.

If the fuel spray is weak or if no fuel spray can be observed during this test, the preheater or nozzle is clogged and should be replaced.

It is recommended to replace the nozzle first and reattempt this test. If the system is still clogged, the preheater should be replaced.

Turn the power off to the unit and contact Lanair by phone or at lanair-dot-com for assistance.

Replace any defective parts and perform this test again

When fuel is flowing properly throughout this test, restore the unit’s installation, settings, and safety features to their operational conditions and reattempt to operate the unit.

If proper fuel spray can be observed during this test, but the unit does not operate correctly when returned to normal operation, further troubleshooting should be conducted. Refer to the product manual, lanair-dot-com, or contact Lanair technical support for further assistance.

We hope this video was helpful in servicing your Lanair Waste-Oil Heater …and getting you back to enjoying America’s best value in heating!