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Ignition

marty D_2
marty D_2 Member Posts: 35
Back on Ignitors again. So, since its the heat given off
by the spark that ignites the oil vapor, what factors can
affect the heat? Excess air, air temp, wider spark meaning
more resistance hence lower current/lower temp? If we have
no ignitor testers that work, is there a way to measure
the "heat" given off by the spark? Still looking for a way
to diagnose intermittant ignition problems with electronic
ignitors. I agree with previous advise to stick with transformers when using intermittant (constant duty) primaries, but the 100 watt power consumption vs. 40-50 is
a concern.

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 10,225


    May not be much help but I no for a fact that the WIDER the gap the hotter the spark.
  • oilman
    oilman Member Posts: 2


    thats not true on the wider the spark the hotter the spark ity depends what kind of oil burner it is let us know then we can help all burners have different electrode settings
  • eleft_4
    eleft_4 Member Posts: 509
    Ignition

    If the burner is set up correctly it only needs 15 seconds of ignition.

    al
  • Rookie_3
    Rookie_3 Member Posts: 244


    AS long as you have a min. 637*F you'll get ignition, even a weak spark could possibly give you that. Getting clean light offs is another story. There are a lot of burners out there that are running but running poorly because someone set the electrodes just good enough to get ignition. The poor electrode settings on intermitten ignition could create more of a problem than a rough start up or puff back by possibly pulling the flame off center and causing impingement.

    ROOKIE
  • A.J.
    A.J. Member Posts: 257
    Ignition problem

    Marty
    1) verify electrode position with burner manufacture wiether it is Carlin, Beckett,or Wayne.
    2)make sure you have a good pair of electrodes(burnt electrodes will not focus the spark as well as a pair of pointy ones).
    3)make sure the nozzle is the correct one.
    4)if it is a iron core transformer test it with a transformer meter that that has a scale (Donagan) makes one
    no screw driver it will not tell you if your at 10,000 V
    5,000 V replace anything below 9,000 V

    P.S don't worry about the differance in power usage you will never miss it

    Kupetz's Plb & Htg
  • RonWHC
    RonWHC Member Posts: 232
    Like your

    "temperature of the spark method" for testing ignitors. 600-700+* works better than 500*. Wider electrode gap, w/ a good ignitor (transformer), is hotter than narrow gap. Many older commercial burners, firing against pressures of +.30" WC & higher, had 12K transformers w/ a recommended 3/16" gap. Same for the spark ignited #4 oil burners. Today, many burner reps. recommend spreading the gap for smoother starts. Most times wider than the specs call for. Of course, today's ignitors are 14K, w/ peaks above that. Looks like we are re-learning what some of the old timers knew. Interrupted ignition anyone?

    JMHO. But, I think the problems we are having w/ transformers & ignitors is that we are sizing the equipment closer to the load than before. In the days of double size boilers, the burners ran shorter cycles. The Massive amounts of metal held the temp longer too. Today, most of us are getting the boiler closer to what the tighter envelope of the home requires. Ergo, longer cycles. Today's ignitors, & less well insulated transformers, can't handle all that sparking. Interrupted ignition anyone?

    And. As boilers & furnaces get tighter, we are doing things w/ air we have never done before. Lots of things going on @ the points of fuel mixture & ignition. The old 1725 beauties would light w/ a 7K jolt. Try that today.

    Think about this. The gas guys use 14K to light a puny little pilot. We light main flame. Once again, interrupted ignition anyone?

    Now, if only you can figure out how to measure spark temp w/ light off air. I might even contribute to the patent process cost. For a piece of the action.
  • marty D_2
    marty D_2 Member Posts: 35
    Temperature test

    Ron
    See thread
    "ignitor temperature" I tested some problem ignitors that
    we pulled from the field and got some interesting results
    testing the spark temp with a standard thermometer from the
    Bach kit. Sure there is a better way to test temp, but it worked.

    marty
  • Read it yesterday.

    I assume the test was done in still air. Learned the hard way, too many years ago, that spark tests (and possibly your temp test) don't always survive when 3450 rpm driven air is added to the equation.

    Maybe you could design a thermocouple based device to slide down the tube to the ignition zone to measure the spark temp w/ light off air. My offer stands.
  • marty D_2
    marty D_2 Member Posts: 35
    temperature of spark

    Ron
    You are right, I really need to test the temp of the spark
    in real life. Do you think there is a direct correlation
    between the temp in ambient air, no forced air, and the temp
    in real life? ( at end of tube)?. It seems that it would
    be valid if there is a thin blue spark, with a low temp
    with the ignitor flipped back, that would mean there is a
    good chance that it would also be low temp with everything
    in place? This is not rocket science. I am going to instruct
    techs to observe the spark visually, and if its a thin blue
    arc at low temp with the ignitor flipped back, then change
    it if we are having repeat calls for off on reset. Do you
    agree with this? Could have them test the temp, but so far
    every ignitor with a thin blue arc, no orange, has a temp
    below the ignition temp of #2 fuel. Guess I could have them
    check the temp, easy as the Back thermometer works fine. So
    far, we have 100% sucess/ no call backs changing the thin
    spark devices for intermittant off on reset calls.
    Marty
  • eleft_4
    eleft_4 Member Posts: 509
    temperature of spark

    > "So far, we have 100% sucess/ no call backs changing the thin spark devices for intermittant off on reset calls. Marty"

    Can you explain this statement? And identify what you are changing, from and to. And what is intermittant off on reset?

    al
  • big bob
    big bob Member Posts: 6
    possible answer

    i recently went to burner class set up by carlin and they advise setting a 3/4 inch gap between the prongs on the ignitor and if spark jumps between the ignitor is good.as far as what could affect the temp all of the items you listed would affect the igntion.every burner manufacturer makes it's own gauge for gapping electrodes and you can order them through a local parts supplier.they are very handy.the ignitors i have used with constant duty primary's have never really given me any problems with bad ignition.i find that setting the electrodes an 1/8 of an inch apart and 3/16 over the tip of the nozzle never give me any problems as long as your air is adjusted correctly.hope this helps.
  • Bob Harper
    Bob Harper Member Posts: 882
    oil ignition

    The average spark is about 1,700F while a HSI runs about 3,400F. A cigarette is 600-800F and a pilot flame is about 2,400F.
    I think you are confusing 2 separate issues. It isn't so much the temp. of the spark but the conditions of when and where. Some of the considerations are:transformer 10-14,000 vac, electrode position, high tension wire condition/connections/shorts, bus bars, ceramic on igniter crazing/dirty, electrode position/gap/ clean/ no pitting, air shutter setting, nozzle pattern in relation to 'trode tips,grounding, etc.

    It takes a lot more power (4-6,000 vac)for an arc to form across a gap than to start off in contact then break contact arcing. However, the temp. of the spark formed is about the same. The size of the spark changes as does the amount of fuel it ignites at the same moment. A small spark may be in position and be hot enough for ignition but the Heat Release Rate of the tiny amt. of fuel involved is not enough to sustain combustion. Thus, the larger spark ignites more fuel which provides the needed Heat both in quantity and rate to support combustion.

    HTH,
    Bob
  • RonWHC
    RonWHC Member Posts: 232
    I would be surprised

    if there was not a difference. The temperature from the spark has to heat the air surrounding it. That temp increase has to be picked up by the stack probe you are using. How much change in fan forced air vs. still air? Is it significant? What is the minimum acceptable temp?

    Looks like you are on to something. However, "thin blue spark" can be subjective. Not kicking. However, it looks like at least one more step is in order. Go get 'em, Edison.
This discussion has been closed.