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Dome vs Surface

Why does my dome read about 50° higher than my surface? Shouldn’t it be the other way around?
Large BGE Dallas, TX

Comments

  • lkapigianlkapigian Posts: 8,320
    edited January 24
    Less dense air rises ...hot air expands and becomes less dense 
    Visalia, Ca

    LGBE- Pit's by Klose Trailer -Stumps XL Stretch - Custom Santa Maria-Modified HD Offset Smoker Reverse Flow- FatStack Smoker FS120 coming soon FatStack 500- Blackstone 36 Blackstone 22 - Custom Cold Smoke House and a lonely Brinkman Vertical Smoker
  • lousubcaplousubcap Posts: 24,622
    Try the search function here (at least visible on the desktop screen) and use this phrase: "dome and grate temperature" .  You will find plenty of threads that will offer explanations.  You may also find some differing opinions about it, not surprising with the BGE community.  FWIW-
    Louisville; "indeterminate Jim" here.  Rolling smoke in the neighbourhood. # 38 for the win.  Life is too short for light/lite beer!
  • bhuggbhugg Posts: 317
    And now I have this.
    Large BGE Dallas, TX
  • bhuggbhugg Posts: 317
    I mean, the egg was basically shut off. The surface temp was sky rocketing and the meat was cooling. It just doesn’t make any sense. 
    Large BGE Dallas, TX
  • buzd504buzd504 Posts: 3,549
    If you quit worrying about grate temp, it makes everything much easier. 
    NOLA
  • bhuggbhugg Posts: 317
    buzd504 said:
    If you quit worrying about grate temp, it makes everything much easier. 
    Will you please explain?
    Large BGE Dallas, TX
  • Mattman3969Mattman3969 Posts: 10,409
    edited January 25
    You are experiencing information overload.  We’ve all done it till it drives us crazy.  I threw away the wires and run all natural and enjoy the egg so much more now.  I chose the dome thermo as my source of info. 

    -----------------------------------------


    2008 -Large BGE. 2013- Small BGE and 2015 - Mini. Henderson, Ky.
  • lousubcaplousubcap Posts: 24,622
    Every BGE has a dome thermo-the accepted practice here is that if a cook temp is offered it is dome unless otherwise specified.  I would gather you have not looked beyond this thread for any insights.  FWIW-
    Louisville; "indeterminate Jim" here.  Rolling smoke in the neighbourhood. # 38 for the win.  Life is too short for light/lite beer!
  • buzd504buzd504 Posts: 3,549
    bhugg said:
    buzd504 said:
    If you quit worrying about grate temp, it makes everything much easier. 
    Will you please explain?
    The subsequent replies explained it very well, but to expand - at any given moment you could take temps at 20 spots in your egg and get 20 different readings. The egg generates convection so the air is moving and temps are fluctuating. The dome temp is the reference that everyone has and whether or not it matches the grate (or any other) temp, it gives a consistent representation of what is happening in your egg. Once you see how your cooks preform against that reference, it becomes reliable. 
    NOLA
  • nolaeggheadnolaegghead Posts: 38,466
    I don't use any thermometers to measure egg temps.  I just make it hotter to cook faster, cooler to slow it down and take it off when it's done.  I will use an instant read for internal food temps.
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  • Mark_B_GoodMark_B_Good Posts: 871
    bhugg said:
    I mean, the egg was basically shut off. The surface temp was sky rocketing and the meat was cooling. It just doesn’t make any sense. 
    What do you mean by surface temperature, you mean the grate temperature, or the dome temperature.

    When the bbq is cooking normally, dome will always be somewhat hotter than grate. Your meat is on the grate and sucking up all the energy. Hot are rises to the dome, then curls back to feed that energy sink (meat).

    If you mean the grate temperature rose fast after you closed the vent, well, sure, that can happen because you basically kill the convection action (no air flow), and so everything initially gets hotter, then eventually cools over time.
    Napoleon Prestige Pro 665, XL BGE, Lots of time for BBQ!
  • alaskanassasinalaskanassasin Posts: 4,668
    what does your gasket look like? install a rutland.
    South of Columbus, Ohio.
  • stlcharcoalstlcharcoal Posts: 4,433
    bhugg said:
    I mean, the egg was basically shut off. The surface temp was sky rocketing and the meat was cooling. It just doesn’t make any sense. 
    What do you mean by surface temperature, you mean the grate temperature, or the dome temperature.

    When the bbq is cooking normally, dome will always be somewhat hotter than grate. Your meat is on the grate and sucking up all the energy. Hot are rises to the dome, then curls back to feed that energy sink (meat).

    If you mean the grate temperature rose fast after you closed the vent, well, sure, that can happen because you basically kill the convection action (no air flow), and so everything initially gets hotter, then eventually cools over time.

    Other way around (in a kamado at least)......dome thermo sits about a big piece of meat sucking up the heat and with liquid evaporating dropping the ambient temp above it as it exhausts.  Unless there is a pit probe sitting right next to the meat, the grate temp should usually be higher as it's closer to the fire, and no evaporation around it.  If it was a reverse flow, or didn't exhaust out the top, then it could work like that.

    But as someone else said, there could be a million different temps, especially in a XL.  Commercial bakery ovens even vary quite a bit.  I used the rotate the grate 180 back in the day, but with the fire moving around in the firebox, it's going to take it's course anyway.
  • Mark_B_GoodMark_B_Good Posts: 871
    bhugg said:
    I mean, the egg was basically shut off. The surface temp was sky rocketing and the meat was cooling. It just doesn’t make any sense. 
    What do you mean by surface temperature, you mean the grate temperature, or the dome temperature.

    When the bbq is cooking normally, dome will always be somewhat hotter than grate. Your meat is on the grate and sucking up all the energy. Hot are rises to the dome, then curls back to feed that energy sink (meat).

    If you mean the grate temperature rose fast after you closed the vent, well, sure, that can happen because you basically kill the convection action (no air flow), and so everything initially gets hotter, then eventually cools over time.

    Other way around (in a kamado at least)......dome thermo sits about a big piece of meat sucking up the heat and with liquid evaporating dropping the ambient temp above it as it exhausts.  Unless there is a pit probe sitting right next to the meat, the grate temp should usually be higher as it's closer to the fire, and no evaporation around it.  If it was a reverse flow, or didn't exhaust out the top, then it could work like that.

    But as someone else said, there could be a million different temps, especially in a XL.  Commercial bakery ovens even vary quite a bit.  I used the rotate the grate 180 back in the day, but with the fire moving around in the firebox, it's going to take it's course anyway.
    I'm talking indirect, and just above plate setter is always measured a good 30F to 50F lower than the dome, where the temperature gauge is.  Heat rises up the side of the bbq, where the gaps in the plate setter are, up to the dome, then curls back downwards and hits the meat, with a portion being bled off via the vent. This is the convective action of the green egg.

    If you're talking direct ... then for sure, grate is going to be hotter than dome, as long as you're measuring away from the heat sink (meat).
    Napoleon Prestige Pro 665, XL BGE, Lots of time for BBQ!
  • Carolina QCarolina Q Posts: 14,822
    As is often the case on here, overthinking temp is rampant. The egg comes with one thermometer. Use it.

    I hate it when I go to the kitchen for food and all I find are ingredients!                                                                                                                                                                                                                           

    Michael 
    Central Connecticut 

  • nolaeggheadnolaegghead Posts: 38,466
    As is often the case on here, overthinking temp is rampant. The egg comes with one thermometer. Use it.

    Right.  You just want to be in the ballpark.

    If you graph temp vs time in your kitchen oven, you will see a sawtooth pattern with a wide swing. 

    For long cooks, the amount of energy going into the meat to do a job is "the cook". 

    If anyone here remembers their calculus, that energy is loosely tied to the area of the graph of the temp over time.  (ignoring many other factors).  You can shorten the time by increasing the temp, and vice versa.

    The evaporative effects are highly dependent on the cooking temp and mass of meat.
    ______________________________________________
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  • nolaeggheadnolaegghead Posts: 38,466
    Yeah Science ****  Know Your Meme
    ______________________________________________
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    Virus downloading.....(*beep...bleep...whirrr...whirrr*)
    Download Complete.



  • One the advantages of Kamado's is that there is multiple sources of heat for cooking your food.  Measuring anyone of these misrepresents whats going on.

    The primary heat sources you use every day are:
    1) Conduction (ie. steak on cast iron).  Heat is transferred surface to surface
    2) Convection (hot air passing by)
    3) Radiant heat.  This one is important and why I like to heat soak my ceramics before putting on my meat.  Like how you get a sunburn in the sun, this is heat radiating from the hot ceramics

    Calibrate your dome spring and fall and don't get two worked up about it, i recommend dome since its there every cook... unless you are going to use an electronic probe every cook, in the same spot it makes understanding whats going on more difficult 
    Two Kamado Joe Classic III & a Kamado Joe Jr.  Large BGE, Mini BGE 
    YouTube: @smokingdadbbq 
    Instagram: @smokingdadbbq  

  • YnoYno Posts: 420
    I clip my pit probe to the dome thermometer stem, and hope they match somewhat closely. But I am not anal about it.
    XL BGE in San Jose, CA. Also a Pit Barrel Cooker, a Cal Flame P4 gasser, and lots of toys including the first ever Flame Boss 300 in the wild. And a new Flame Boss 500.
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