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Dome vs Grid temp

carbajc8carbajc8 Posts: 6
edited June 2012 in EggHead Forum
It's my first cook on my new large egg!  Have a spatchcocked chicken on, and I'm trying to regulate the temperature.  I have a Maverick hooked up and the BBQ sensor clipped above the grid slightly off center.  It has been reading 336 for about a half hour without change.

However, the dome temp seems to be reading around 380.  I've checked the BGE thermometer with another digital probe I have, and it also reads 380.  

Is it normal to have a 40 degree difference between the rack temp (I'm using the highest position on a large adjustable rig and cooking direct) and the dome temp?  Or am I doing something wrong?

Comments

  • lilwootylilwooty Posts: 215
    edited June 2012
    Not that unusual. I calibrated my dome thermometer twice because I thought it had a problem, but after I verified temps on both grid and dome with other thermometers, I still have almost a 40 degree difference on my XL. I stopped worrying about it and just remember to account for the difference when cooking.

    Living Large and XL

  • lousubcaplousubcap Posts: 14,634
    Classic BGE temp difference-especially if indirect-you can expect that kind of delta T when first firing it up. The longer the dome is closed the closer the temps. FWIW-almost all cooks posted reference the calibrated dome temp as every BGE owner has that indicator. Believe your indications until proven wrong.
    Louisville;  L & S BGEs, PBC, Lang 36; Burnin' wood in the neighbourhood. # 38 for the win.
  • GriffinGriffin Posts: 7,616
    Just stepped back inside from having a smoke. I've got MOINK balls going on right now and I was thinking about the same very thing. I've actually quit looking at the dome temp (at least on low and slows when I have a probe going). I'm not cooking food at the level of that dome thermometer. I've got my pit controller at the grate level running at 247 right now and the dome is at 290. I go by grate level and all my low cooks are referenced at grate level not dome temp.

    Rowlett, Texas

    Griffin's Grub or you can find me on Facebook

    The Supreme Potentate, Sovereign Commander and Sultan of Wings

     

  • stikestike Posts: 15,597
    I think the logic is that dome temps have always been referenced, before the difference was known. Which means that if you are used to an 'old' dome temp of 250, it doesnt necessarily mean the target at the grate should be 250. Which would mean then raising dome temps to achieve 250 at the grate.

    250 isnt the desired temp for ribs necessarily at the point where they are. It's just a reference.

    Just as 95 in the sun and 80 in the shade doesnt mean the sun is 95 degrees. Just a relatively arbitrary point of reference

    ed egli avea del cul fatto trombetta -Dante
  • lousubcaplousubcap Posts: 14,634
    @ stike-well-said.  All you need is a reference, then adapt accordingly.  Can't be that difficult-can it?
    Louisville;  L & S BGEs, PBC, Lang 36; Burnin' wood in the neighbourhood. # 38 for the win.
  • AD18AD18 Posts: 209
    Always trust the grate temp.  Grate temp on a Maverick should be pretty much spot on.  Starting a cook will have a fairly wide variance between grate and dome temps, sometimes 40-50 degrees, but as time passes the two will gradually get closer together.  However, I've never seen the two equal, closest I've seen  is about 20 degrees hotter on dome. 
    Large BGE, Weber 22.5 kettle, Weber Genesis
    Cobourg, Ontario
  • carbajc8carbajc8 Posts: 6
    Thanks for all the great advice.  Just trying to get the hang of things... good to be able to draw on the knowledge of the experts here. 

    Things turned out great.  Chicken was bone-clean in 15 minutes!  Then grilled some pineapple rings for dessert.


  • DuganboyDuganboy Posts: 1,118
    I have had a BGE for years and didn't realize the difference in dome and grate temp until I got on this forum very recently.

    I have an electric smoker and when I would do something on them it seemed to get done so much faster.  Now I know why. 
  • MrCookingNurseMrCookingNurse Posts: 4,613
    Just did my first low and slow. Exactly what everyone else has said. Maverick grate temp was 225-280. Dome temp ranged from 250-375. My mind was blown until I just thought about heat distribution and indirect all that jazz makes perfect sense. Longer the cook went closer it got. Last two hours I was like 200 grate 225 dome


    _______________________________________________

    XLBGE 
  • NDGNDG Posts: 1,547
    What is the cheapeat tool I can purchase to measure and monitor grate temp? I have digital instant splashproof thermopen and a thermoworks meat probe (that stays in meat when cooking under 300) so hoping this is the final cheap therm product I need. People mention maverick but website has lots of models. For my needs, what do you think is best?
    Columbus, Ohio
  • gte1gte1 Posts: 376
    It is strange but I have seen fairly large differences, to none at all, to actually higher at the grate. Haven't done enough low and slow cooks with the Maverick to see if there is any consistency in my type of setup realtive the differences in temp.

    George
    George
  • The Naked WhizThe Naked Whiz Posts: 7,780
    The point here is that if a recipe says cook with a plate setter  and a dome temp of 300, you should get the dome thermometer reading 300.  If it says cook direct on a raised grid at 400, you should get the dome thermometer to 400.  You shouldn't be trying to figure out how the dome and grid temperatures differ and adjust the dome temp so that the grid temp is 300 or 400.  In essence, follow the instructions.  On the other hand, if the recipe says good on a raised grid and specifically says that grid temp should be 350, then again, follow the instructions and make the grid temp 350.  Trying get the grid temp to a certain point by getting the dome thermometer to read some adjusted value based on what you think the difference is is a lost cause.  The difference changes during the cook due to any number of reasons.
    The Naked Whiz
  • Doc_EggertonDoc_Eggerton Posts: 5,106
    Interesting discussion, and I will try to be more specific when I post my own cooks.  I use the Maverick on the grid for all cooks except searing, because it lets me work inside while monitoring the Eggs heating up, and then for the cook., so my recipies are almost alway temps at the grid.  I have not specified that.

    XLBGE X 2, LBGE (gave this one to my daughter), MBGE and lots of toys

  • stikestike Posts: 15,597
    doc. i used to stick the mav probe thru the thermo hole in the dome.
    ed egli avea del cul fatto trombetta -Dante
  • Hi54puttyHi54putty Posts: 1,871
    I always drop the probe through the DW on low and slow cooks to about where the BGE thermometer is.
    XL,L,S 
    Winston-Salem, NC 
  • NDGNDG Posts: 1,547
    Maverick 732 ?
    Columbus, Ohio
  • NibbleMeThisNibbleMeThis Posts: 2,293
    @NDG - The cheapest thing I've seen for monitoring grate temps is an oven thermometer.  I picked mine up for about $4 at the grocery store and it is still working a year later.  I cook mostly by dome temps but I like to know what is going on at the grate level too. 
    Knoxville, TN
    Nibble Me This
  • rickHPrickHP Posts: 49

    I'm sort of puzzled that the dome temps would be higher than the grid temps, or is this only when using the platesetter and the heat gets deflected to the sides?

    But this explains to me why the first thing I cooked on my Egg went wrong. I had been very successful cooking babyback ribs indirect on my Weber kettle at a grid temp (using an oven thermometer) of 275 for about 2 1/2 hours. I thought no way do I have to cook ribs for 4+ hours on an Egg at a dome temp of 275. So I pulled them a little after 3 hours and they were not tender, so I guess the grid temp was a lot lower than 275.

  • lousubcaplousubcap Posts: 14,634
    @rickHP-it definitely occurs with the indirect setup and before I figured it out had the same screw-up as you did with a low&slow rib cook (can't be taking this long...oh, yes it can).  BGE should include that bit of info in their literature-doubt most dealers would know or care.  Don't know about direct cooks as the temps/times  are such that a few degrees won't make much difference.  I'm sure someone has measured it but I'm not one of those.
    Louisville;  L & S BGEs, PBC, Lang 36; Burnin' wood in the neighbourhood. # 38 for the win.
  • The Naked WhizThe Naked Whiz Posts: 7,780
    Heat rises.  No surprise.  (As long as the fire isn't terribly hot and radiant heat comes into play.)  I guess I'll have to whip out my tools and do a little 'vestigatin'.
    The Naked Whiz
  • The temp difference between the grill and dome is not unique to the egg. I learned this lesson a few years ago while doing my first cook on my old offset barrel smoker. The stock thermometer was placed high in the smoke chamber, I cooked ribs at 220, but the grate temp was probably around 180, I cooked those ribs for at least 10 hours, ended up throwing them out.
    The reason for the difference is that heat rises, and the hot air accumulates at the top.
    Simi Valley, California
    LBGE, PBC, Annova
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