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Dome/Grill temp differential.

transversalInactivetransversalInactive Posts: 376
edited 1:31PM in EggHead Forum
Since acquiring my first BGE Large right after Christmas, I have used my Egg many, many times. I have managed to ace everything that I have attempted.....from brisket to butts to pork loin to lamb legs to chicken, etc. About 4 weeks back, I bought a Maverick ET 732 and have been using it every weekend, to allow for shut eye during my all night low & slows.

I have noticed a consistant and sizable temp differential between the dome BGE thermometer and the 732....as much as 60 degrees, until I recalibrated the BGE thermo yesterday. I found it was off by 30 degrees, although I calibrated it upon receipt of the grill. That reduced the differential a good bit.

Current reading on the grill BGE is at 250*, while the 732 is reading a consistent 214* for the last 45 mins. The 732 heat probe is clipped to the grill away from the pan and food (3 slabs baby backs) with the cable shielded by the plate setter from a traditional "hot spot" (between plate setter legs).

Here's my question. Is it posible that there is that much differential between the dome temp (BGE thermo reading) and the grill level temp (732)? While I have been able to narrow the gap between the two, I cannot account for the remaining difference. There is consistent disparity in readings over many cooks, and many different target temps, with many different foods. I cannot account for the difference other than stratification in temps within the egg or a deffective BGE thermometer, or a defective 732 probe or unit.

Help!! If I can't get an answer on this site, I will accept that one doesn't exist. Thanks in advance.

Comments

  • dhuffjrdhuffjr Posts: 3,182
    Heat rises. The dome temp is going to be higher. 40-50 degrees is the rule of thumb I remember and that is about what your seeing. Sometimes you'll see folks using tools to get you higher up in the dome to capture that extra heat and reflected heat from the dome.
  • fishlessmanfishlessman Posts: 21,552
    what you found is actually true, colder down lower with that setup. most recipes here are posted as dome temps to help it be less confusing. if there were no inderect setup, the 732 would read higher than the dome at the grill level, the inderect setup redirects the heat out to the edges and up and the cold meat helps to trick the reading even more
  • I had absolutely no idea that the difference in temps between dome and grill could be that great........but it makes sense that there would be a difference......just didn't think that much.

    Since I can't calibrate the BGE thermo, I guess I just have to interpolate the difference in the two reads to make the 732 read meaningful.

    I have read where some have tried removing the BGE termo temp probe and inserting the maverick probe in its place, but I have never heard whether or not it works acceptably. Sure hope somebody is reading this string who has given it a try.

    Thanks.
  • gdenbygdenby Posts: 5,565
    You are doing much the same thing I did early on. I found, as already mentioned, that the probe would register temps lower than the dome in an indirect cook, and higher with a direct.

    The rule of thumb is that the raised grill level temperature is about 25 degrees cooler than the dome.
    In an indirect cook of many hours (any lo-n-slo) the temp at the raised grill and the dome will just about meet.

    And for really screwy reading, have a big piece of cold meat almost touching the dome therm!
  • Excuse my error....meant to say, "Since I can't calibrate the 732......"
  • No, friend....already been down that road. That's not the problem.
  • fishlessmanfishlessman Posts: 21,552
    you can still test the 732 in boiling water, i bet its really close, close enogh that you wont worry about it, if it is really off i would be calling maverick
  • Thanks to all of you for taking time to respond.
    At least I can assume for the time being that my thermos are working as they should, and I will take the suggestion to give the Maverick the boiling water test. In any event, the gap between the two still exceeds 25* and I have never seen the two come close ......even on the lowest and longest cook.

    I love the BGE. I've owned a bunch grills in my day, but the BGE has just totally redefined usage of my days off, weekends, etc. I now see the night before a day off as a time to stoke the charcoal and head to the butcher. And my most relaxing hours are spent learning from the masters on this site. Ain't life fun with a BGE!!
  • fishlessmanfishlessman Posts: 21,552
    my bge therms never held a calibration, they were off every cook, bought a teltru gage for the dome and never looked back, always dead on when i checked them.
  • Fishless, would you please give me the model number of your teltru? My BGE dealer down the street stocks some fo them.......but I read several posts about which is the correct one to use. I would appreciate it if you would share that info with me. I was amazed that my BGE termo was off 30 degrees, having just regulated it 2 months ago. Thanks.
  • fishlessmanfishlessman Posts: 21,552
    i use the one with the 2.5 inch stem, it reads low by a little over 10 percent. the one with the 5 inch stem reads right in the egg, most put a 1 inch spacet between the gage and the outside of the dome to make it similar to the bge 4 inch gage. im happier with the smaller gage as i used to break the longer ones, its off but i can easily compensate by adding ten percent to the reading
  • Nature BoyNature Boy Posts: 8,437
    Hi Sophie.
    There are an infinite number of factors involved. I generally put 2 different probes at the grate level a few inches from the meat (especially when we compete). There can be a huge difference between dome and grate temps, and also a big difference between the two grate probes from left to right (or back to front). All depends on your setup and how and where your fire is burning hottest. Cold meat mass makes the difference more dramatic.

    No magic to it, just be paying attention. You'll start seeing some patterns after a while if you're monitoring.

    Happy cookin!
    Chris
    DizzyPigBBQ.com
    Twitter: @dizzypigbbq
    Facebook: Dizzy Pig Seasonings
  • Thanks, Chris.........I do monitor very closely, but I'm trying to get it down to where I can sleep though an all niter without the investment in something as expensive as a guru. Now that I understand what's going on, I'll find a way to deal with it. I'm hoping fishless tells me what model number teltru thermo to buy for a large..........

    Thanks for the input, friend.
  • Thanks, fishless.......works for me.......appreciate your time and help.
  • fishlessmanfishlessman Posts: 21,552
    LT225R is the 5 inch stem that everyone buys to replace the bge gage
  • Nature BoyNature Boy Posts: 8,437
    No problem Jack. But the sleeping through the night thing is different than the done vs grate thing.

    You want to sleep through the night, the Guru is pretty sweet.

    Cheers
    Chris
    DizzyPigBBQ.com
    Twitter: @dizzypigbbq
    Facebook: Dizzy Pig Seasonings
  • Wise OneWise One Posts: 2,645
    Jack - We had a huge discussion on this topic about four to five years ago. Most people noticed anywhere from 15-30 degrees difference depending on several factors. It also explains why when people try to hold their dome at 220, they have trouble getting their meat above 190.

    BTW, it's good to see you posting even if you have to hijack your wife's handle to do so. Bill
  • BikeHikeBikeHike Posts: 10
    I had a similar experience when I did two Boston Butts. I started them around 9:00pm at night and the next morning I was watching it and was noticing that the temp on the dome was going down my DigiQ was still right at 225. When I'm BBQing I like to put my hands on the EGG because it keeps them warm and that's when I noticed that there was a hot spot on the side I had the Digi therm placed on the grill. I moved it to the other side and it started picking the temp up again and finished my low and slow correctly.
  • fishlessmanfishlessman Posts: 21,552
    on an overnight i dont watch it so closely, i set my low alarm at 190 and high alarm at 280 and shoot for a cook somewhere around 240. in the morning ill make an adjustment :laugh: :laugh: just so you know,overnight low and slows are not that exact temp wise
  • fishlessmanfishlessman Posts: 21,552
    if you put 4 or more in there it is pretty much impossible to get a good reading, touching the dome and getting a look at the fire can be more accurate ;)
  • Oh I know it's the way to go, but that's a down the line for me....may Christmas or something. It's pretty expensive, so I'm told.
  • You sure make me feel better, Fishless.......I was over here wondering if I was out'a sync with the rest of the Egging world........I feel better knowing that others experience some of what I do. Thanks again. Feel like I'm making some good friends on here.
  • Bill!! Just realizing who you are, friend!! Nice to talk to you again!! Actually, somewhere in the sign on disaster, she used our oldest grand daughter's name (Sophie) in the wrong box.....hence the name!! I can imagine what the heck people are thinking out there, but I am afraid to try to change it. Thanks for saying Hi. I'm lovin every minute of my Egging, and I really like the folks on this site. Take care friend.....hope all is well with you and family.
  • Thanks, Fishless.....you're a good man!!
  • I don't have a digi-q......but I too have experienced hot spots when feeling up the grill..........Well....you know what I mean!!
  • Fishless, I just ordered one from the manufacturer. I guess it will take a week or so to get here. LT 225R, 5 inch stem. If the stand off proves bothersome, I'll replace it with the one you are using. Planning on using a rubber stopper as a spacer, drilling out the hole to accommodate the stem. I'll let you know how it turns out.....unless you have a better idea for a spacer....if so, please tell me. Thanks for all the good advice. Will be lookin for you in the forum.
  • I used a wine cork, was free and works just fine.

    Doug
  • BacchusBacchus Posts: 6,019
    A thermometer will have no influence on the ability to go overnight without making adjustments. And I am not totaly convinced that a Guru will either, at least not on a Big Green Egg. I have done several dozen BGE overnighters and all but one time the needle was pegged at 250ish without moving. The other time the fire had gone out but dome temp was still at 200 when I checked in the morning. There are many stories of fires going out WITH a Guru in use also. Set it and forget it, sans Guru or grid probe....IMO.
    FWIW.....when I did care about grid temp, I once experienced a 100deg differential betwwen grid/dome. All devices calibrated and double checked with Thermapen.
    The best advice I ever got on this forum came from a long time member who said "To Hell with Grid Temp". I chunked the Maverick almost 3 years ago and haven't regretted it once.
  • Damn good idea, Doug. Thanks.
  • Interesting perspective, Bacchus. In most of my all-niters --- and I haven't done as many as you --- I have had only one experience where I spent the night chasing the target temp all over the dial. Since then, I have listened to many who know more than I about about prepping the fire box a little differently for all-niters and a few other tricks that have seemed to allow me to get some shut eye. I can't afford a guru right now, so it's a moot topic for me. But, I'm glad to hear tha I am not missing out on the do all and end accessory by not having one.
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