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Burping Egg

SqueezeSqueeze Posts: 707
edited 3:32AM in EggHead Forum
I know many of you have had the jet engine flame coming out the top of your egg, but has anyone experienced flames shooting out the bottom vent? I have had this happen to me three times in the last week. My set up is an inverted platesetter, grill, food, grid extender, food. Temp only around 375 degrees. Had to keep the dog away as I was afraid she would get some singed eyebrows too. Any ideas on what causes this and how I can avoid hairless shins and knees in the future? Thanks![p]-Kevin

Comments

  • The Naked WhizThe Naked Whiz Posts: 7,780
    Squeeze,
    Yes, I've seen this. Usually it happens when there is a good fire burning, using new lump and the air flow is restricted suddenly. Fresh charcoal is full of volatile organic compounds that burn with a blue dancing flame when the fire temperature gets up to a certain point and these VOC's ignite. Used lump has a smaller quantity of VOC's and if the lump has been burned enough, you can't even force a flashback if you try. (I know, I tried, I failed.) When you restrict the air flow, the burning VOC's can be forced out the bottom vent. If you open the top up and restore the air flow, the VOC's burn up instead of being force down and out. I don't believe I've ever seen the flames out the bottom from a normal fire in a steady state. It has always been after I restrict the airflow. That's my experience...
    TNW

    The Naked Whiz
  • Squeeze,
    Wow, big flames at only 375? And out the bottom? Sounds to me like you somehow have managed a down draft- which i guess would make sence. If the heat draft was going down, most of the heat would be going out the bottom, rather than past the thermometer- so you could have a really hot fire and not a very high dome temp. Perhaps since you have 2 layers of food you may be sealing off the top chimney? Have you cleaned out the ash- maybe something in the ash area is catching on fire.
    Just some random guesses- sounds like you have Big Green Gremlins (I knew someone who had one of those one- I always told him it just needed some flames and it would run much better. . . . . .)

  • jwitheldjwitheld Posts: 284
    Squeeze,
    its got to be too much restriction on the outlet vent (daisy wheel, slide top). as the whiz mentioned there will be a buildup of hot voc's and these will be hungry for air.
    It does seem like excessive voc's, what fuel are you using? and did you add smoke wood? you mentioned food but didnt eloborate, fat may be involved.

  • SqueezeSqueeze Posts: 707
    jwitheld,
    I was using BGE brand lump, no smoking wood and cooking biscuits and bacon (maybe the bacon and its fat did it). Nothing too fancy, but it was like a flame thrower.

  • QBabeQBabe Posts: 2,275
    Squeeze,[p]When it happened to me, I was cooking 2 spatchcock chickens direct on a raised grid. No platesetter, no pizza stone...just the chickens filling up the grid. I had gotten it up to 350° and put the chickens on just like normal. I kept wondering why the temp wouldn't rise, so kept tapping the vents opem more and more. Then after about 15-20 minutes, all of a sudden, it started thumping like mad and WHOOOOOOSSSSHHH, flames shot out of the bottom vent at least 3 feet. Next thing I knew, my dome temp shot up to about 650° and I had to close it up quite a bit...[p]To this day, I have no idea why....[p]Tonia
    :~)

  • The Naked WhizThe Naked Whiz Posts: 7,780
    WailingAngusBeef,
    It don't believe it is a down draft, per se. Rather, when the VOC's ignite, there is a large increase in temperature which causes the gases in the egg to expand rapidly. If the vent is the easier way out of the egg, the burning VOC's exit there.[p]TNW

    The Naked Whiz
  • jwitheldjwitheld Posts: 284
    Squeeze,
    this happened when it was just sitting there or had you just closed the top or closed the upper vent?
    this is really interesting

  • SqueezeSqueeze Posts: 707
    jwitheld,
    I was sitting there. The top was wide open and the bottom was too.

  • fiver29fiver29 Posts: 627
    Squeeze,[p]I have had this happen a few times. I figured that once the temp started to rise with both vents wide open with fresh lump it will happen if you place a barrier in there (ie. platesetter, butterfly chickens that cover up most of the grid, etc.)[p]Now I can't explain the laws of physics for this happening. If it happens it happens. What I was mostly interested in is how to reduce the liklihood of it happening again. I have 2 ways that I reduce it.[p]First, using lump that isn't fresh. I have never had a reverse flashback (that's what I call it) with lump that has been used at least once. Second, because the first choice isn't always an option I developed step number 2. [p]Once the egg gets to the desired temp (lets say 350*), I let go up 100* past that. So at 450* I completely close the bottom vent and keep the top vent completely open. I let it sit for about a minute and then I 'burp the egg' opening it slowly. At some point the charcoal catches fire while opening and that is to be expected. I put the platesetter in and clost the lid.[p]At this point I keep the top vent wide open and I open the bottom vent a small crack. The temp will stabilize around 350* and won't get a reverse flashback 99% of the time. I say 99% of the time because one time a little iddy-bitty flame shot through the small crack at the bottom.[p]Within 30 minutes or so and the temp fire has reached steady state as someone else put it there is no issue at all. So, this method reduces the chance of a reverse flashback most of the time. If it happens at all this way it will come out a very small crack and shouldn't be an issue anyway.
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