Author Topic: Ignitors  (Read 4134 times)

Russ

  • Administrator
  • Can't stop the fire now!
  • *****
  • Posts: 481
    • View Profile
Ignitors
« on: March 17, 2013, 11:00:30 am »
Here is some information from Beckett's site:

 FEATURES OF ELECTRONIC IGNITORS

  • mount on a burner housing baseplate similar to that of a transformer.
  • are smaller (1/4 to 1/2 the size) and weigh less than a transformer (1 lb. compared to 8 lb.).
  • have oil ignition characteristics similar to that of a transformer.
  • offer improved performance with cold oil or delayed spark conditions.
  • have output currents and peak voltages that can be up to double that of iron core transformers.
  • produce a spark intensity that can be less sensitive to line voltage fluctuations.
  • are epoxy sealed for moisture resistance and have oil-resistant, non-rusting plastic enclosures.
  • consume 50 to 75% less power than transformers.

IRON CORE TRANSFORMERS draw 120 VAC (Volts, Alternating Current) into their primary coil. The steel plates of the transformer core transfer the primary coil's 60 Hz magnetic field to the secondary coil. The secondary coil uses this field to produce a high output voltage of 10,000 VRMS open circuit (when there is no secondary current flowing) that has a frequency of 60 Hz.

ELECTRONIC IGNITORS receive 120 VAC and change it to DC (Direct Current) voltage inside. The DC voltage turns power transistors on and off very quickly, conducting current through the primary coil of its small internal transformer at a frequency of 15,000 to 30,000 Hz. The secondary coil of this special high frequency transformer produces a high voltage ignitor output that has a frequency of 15,000 to 30,000 Hz.

Remember: the ability of an ignitor to ignite oil depends on more than just high voltage - it depends on arc output current as well! Spark heat energy = voltage x current.


The electronic ignitor does not require extensive maintenance. However, there are areas to consider:

  • Similar to the iron core transformer, the electronic ignitor must be kept clean and dry. Prolonged exposure to moisture can cause arc tracking and potential failure. Wipe dirt and oil from all surfaces.
  • Check insulator bushings and make sure they are clean and free from any crazing or cracks. Replace units that show evidence of damage.
  • Examine the ignitor input leads for cuts or tears in the insulation. Route the leads securely so that they are not pinched when the ignitor is closed. Make sure the wire nuts are tight and no bare wires are exposed.
  • If the ignitor has gasketing, check the sealing surfaces and replace any suspect gaskets. (Use gasket kit No. 51304 for AF and AFG burners.)
  • The secondary electrode springs should be clean, should be aligned perpendicular to the ignitor base, and should make solid contact with the burner electrode rods when the ignitor is in the closed position. If the springs makes poor contact, the ignition performance could be impaired.
  •     Perform the following test to check that the ignitor is grounded to the burner. Turn off the power to the burner. The Ohmmeter resistance between an electrode spring and the exposed metal of the burner (for instance, the copper line or a housing bolt) should be less than 2000 Ohms. If this resistance is infinite, the ignitor is not grounded to the burner. Note: This resistance should be the same as the other spring-to-burner resistance, and it should be 1/2 of the spring-to-spring resistance. If the two spring-to-burner resistances differ by more than 20%, the ignitor should be replaced.


HOW TO TEST ELECTRONIC IGNITORS
Just like an iron core transformer, an electronic ignitor is most simply tested by supplying it with 120 V input and observing whether it produces an arc. This may be done by looking or listening to see if there is an arc across the electrodes while the burner is running and the ignitor is energized. Secondly, the ignitor may be tilted back on its hinge and, when voltage is applied, the blade of an insulated screwdriver may be placed across the springs to test for an arc. NOTE: The cad cell will not permit the primary control to energize the ignitor if the cad cell senses light. Therefore, before you perform this test, disconnect one lead of the cad cell from the primary control, or remove the cell from its base. Remove power from the rest of the burner and disconnect the fuel supply from the nozzle line while performing this test. SHOCK HAZARD: Though this test is common industry practice, be careful not to physically touch any part of your body to the ignitor springs or anything metal that is touching the ignitor springs while the ignitor is energized. DO NOT use transformer testers to test electronic ignitors. Doing so will give you an inaccurate measurement and may harm the ignitor, the transformer tester, or both.

If an ignitor fails, it generally produces no arc at all. However, similar to an iron core transformer, an electronic ignitor can have a weak output arc. To test for this, perform the screwdriver arc test described above. Energize the ignitor and place the blade of the insulated screwdriver across the springs. Keeping the blade in contact with one of the springs, slowly pull the blade away from the other spring, drawing an arc from the spring to the blade. With a 110 V to 120 V input and no air flow across the arc, the ignitor should be able to maintain an arc with the screwdriver blade at least 3/4" away from the spring. If the ignitor is not able to sustain a 3/4" spring-to-spring arc, or if an arc drawn from one spring to the grounded baseplate is weaker than an arc drawn from the other spring to the baseplate, replace the ignitor.

Electronic ignitors have proven to be durable, effective ignition components. They have achieved wide acceptance in the oilheat industry. Hopefully, this bulletin has further acquainted you with important features, performance, and service aspects.