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My BBQ probe is saying that my dome is 90 degrees hotter than my built in thermometer

Is this normal?  And if so which one should I trust?

I'm cooking a pork butt right now (Started at 6:45am-ish) that's a little over 6 pounds and the internal temp is 140.  I've had the temp stuck at 250 on the dome thermometer, but my remote thermometer's BBQ probe is saying it's 340.
Florida
1 Lg BGE
Pulling my own pork since 2014

Comments

  • dlk7
    dlk7 Posts: 1,053
    Check both of your thermometers in boiling water.  The one in your dome is adjustable.

    Two XL BGEs - So Happy!!!!

    Waunakee, WI

  • grege345
    grege345 Posts: 3,515
    Platsetter placement and probe location can be the culprit. It's all in the placement. Also the temps will differ if everything is set up right but the temp gap will close as the cook goes on. 90 degrees seems to be a big gap

    LBGE& SBGE———————————————•———————– Pennsylvania / poconos

  • Ozzie_Isaac
    Ozzie_Isaac Posts: 18,942
    edited March 2015
    They all nailed it.  Verify cal on probes and gauge with boiling water.

    Also make sure the platesetter leg shields the temp gauge in your dome.  I use a pizza stone so I have no legs.  I use a fire brick to shield the temp gauge.  Also make sure your digital probes are not subject to direct radiant heat from the fire.

    My grate temp and dome temp run 50 to 100 deg F delta for a few hours depending on temp.  They will eventually match.
    A bison’s level of aggressiveness, both physical and passive, is legendary. - NPS
  • RRP
    RRP Posts: 25,880
     delta ???

    That engineer slang?
    Re-gasketing America one yard at a time.
  • lousubcap
    lousubcap Posts: 32,168
    edited March 2015
    @RRP- definitely Greek at a minimum :peace: (Edit):  Make sure your instruments are calibrated and then go with whatever you like.  There are thermo gradients within the BGE.  For me-better to have one thermo I can trust than two that read differently.  You can get too much info...FWIW-
    Louisville; Rolling smoke in the neighbourhood. # 38 for the win.  Life is too short for light/lite beer!  Seems I'm livin in a transitional period.
  • bigalsworth
    bigalsworth Posts: 685
    ∆t
    Large BGE
    BBQ Guru DigiQ II

    Martensville, Saskatchewan Canada
  • RRP
    RRP Posts: 25,880
    edited March 2015
    lousubcap said:
    @RRP- definitely Greek at a minimum :peace: 
    Wouldn't surprise me that Ozzie was a member of Delta Tau Chi =)



    Re-gasketing America one yard at a time.
  • DoubleEgger
    DoubleEgger Posts: 17,125
    Delta T pays my bills....
  • Jeepster47
    Jeepster47 Posts: 3,827
    Delta T pays my bills....
    Ditto ...

    Washington, IL  >  Queen Creek, AZ ... Two large eggs and an adopted Mini Max

  • is there any way to calibrate a maverick thermo?
  • jfm0830
    jfm0830 Posts: 987
    edited March 2015
    While it could be some of the things mentioned, I found huge differences too using thermometers that were calibrated correctly. About a year ago I had trouble making Holiday baked goods in November and December of 2014. The identical items had come out fine in the same period in 2013. In 2014 was getting burned bottoms and under cooked tops. The same items were perfect in 2013. I tried everything I could think of, platesetter legs up, legs down, different pans. What I finally discovered was that the weather was quite a bit colder than the year before. in 2013 it was mid to high 20's and in 2014 it was single digits.  So it was taking the dome thermometer more time to get within the same ballpark as the grate level. This meant the grate temps were too hot. I discovered this by putting a calibrated thermometer at the grate level and there was often a very large difference. The two do balance out over time and get within 20-25 degrees of each other, but it takes a long time in the cold weather and/or if you open the lid a lot.

    I never understood why on the BGE everyone tended to use the dome thermo. I had always been taught that you measure the cooking temp at the level you're are cooking at...the grate level. Since there were other things you do differently with the Egg, I went with the flow and used the dome thermo. When I started having issues and discovered the huge temperature discrepancies, I switched to putting a temperature probe right at my grate level. It solved all of the problems I was having at that time and I haven't had a single problem since. I know conventional wisdom with the Egg is you use the dome thermo, but I don't care. I have a 100 percent success rate. Just make sure your grate thermometer is accurate. The only time I might use the dome thermo is if I am using the AR with the rig extender to cook high up in the dome at the same level as the dome thermo. Your mileage may vary.

    Jim
    Website: www.grillinsmokin.net
    3 LBGE & More Eggcessories than I care to think about.
  • Jeepster47
    Jeepster47 Posts: 3,827
    @jfm0830 ... agree with what you've written above.  Although you didn't state it, your discussion used indirect cooking as an example.  Indirect cooking seems to amplify the differences between grill and dome temps.  Also, plate setter leg placement (for the dome thermometer) and grill probe placement greatly affects the temperature measurements.

    The same situation exists with direct cooks, just not as apparent ... yes?

    Good write-up.

    Washington, IL  >  Queen Creek, AZ ... Two large eggs and an adopted Mini Max

  • lousubcap
    lousubcap Posts: 32,168
    With regard to cooking temp-it is just a reference to what is happening within the BGE.  As long as you know your BGE performance from whatever temp measured from whatever device placed wherever then it really doesn't matter the temperature input source.  Just an opinion... 
    Louisville; Rolling smoke in the neighbourhood. # 38 for the win.  Life is too short for light/lite beer!  Seems I'm livin in a transitional period.
  • grege345
    grege345 Posts: 3,515
    RRP said:
    lousubcap said:
    @RRP- definitely Greek at a minimum :peace: 
    Wouldn't surprise me that Ozzie was a member of Delta Tau Chi =)



    I Disagree. I think he fits in with these guys
    I think @Ozzie_Isaac is the holding the sign
    LBGE& SBGE———————————————•———————– Pennsylvania / poconos

  • Ozzie_Isaac
    Ozzie_Isaac Posts: 18,942
    @grege345 how did you find that pick :blush: 
    A bison’s level of aggressiveness, both physical and passive, is legendary. - NPS
  • jfm0830
    jfm0830 Posts: 987
    @Jeepster47  Thanks and yes the same thing is true with direct cooks. I don't worry so much about those. I get it in the general ballpark with the dome thermo but hold my hand over the grill and do the 1-Mississippi, 2-Mississippi count test.

    @lousubcap I am going to have to respectfully disagree with you. The level you're are cooking at is the most important, because if you measure your temps there you will always be accurate. It would be one thing if the dome temp was always a consistent amount different than the grate level temp. Grate level plus 25 say. Eventually over time they get close, but early on they can vary widely as I have seen first hand. Not so much in warm weather but in the real cold for sure. I will also use the example of my last smoker ,which was a horizontal offset barrel smoker made of metal. I always used my ET-732's grate probe to measure the temps at the grate level. On a cold day the dome thermo on that unit could run 75 degrees lower than the grate level temp. On a warm day when the direct sun hit the top lid, the temps would run 75 degrees high. This is a 150 degree variation depending on weather. By measuring at the level you cook at it simplifies everything and gives you consistent results. Sure you can also very time to make up for temperature but only to a point. Like i said I have been standing out at my Eggs doing some task and it is always interesting to see the wide variance you can get between dome and grate level temps in the cold weather. It goes down over time, but baked goods are sometimes on for only 20 or 30 minutes. If using the dome thermo works for you, by all means use what works. I used it for a year, but suddenly in the real cold weather I was getting breads and desserts that were burning on the bottom and undercooked on top. I was letting the dome thermo get up to 350, but early on in the cook this meant my grate was at 425 to 450.



    Website: www.grillinsmokin.net
    3 LBGE & More Eggcessories than I care to think about.
  • lousubcap
    lousubcap Posts: 32,168
    @jfm0830- Gotta admit I have not worried about the off-sets that you describe, although I do know they exist.  The largest concern is with a low&slow cook and I generally give the BGE at least an hour to stabilize.  As you note-go with whatever works.  That said, the only thing I "bake" is pizza so the temperature variations don't have such an impact.  But as long as you are driving by one speedo and not multiple then you are home-free.
    Louisville; Rolling smoke in the neighbourhood. # 38 for the win.  Life is too short for light/lite beer!  Seems I'm livin in a transitional period.
  • NPHuskerFL
    NPHuskerFL Posts: 17,629
    :lol: ΔT reference didn't even phase me when is was reading this. Use that a lot. @Ozzie_Isaac
    LBGE 2013 & MM 2014
    Die Hard HUSKER & BRONCO FAN
    Flying Low & Slow in "Da Burg" FL
  • jfm0830
    jfm0830 Posts: 987
    @lousubcap If what you do is working for you then that is great. The bottom line is how the food turns out. I can work with a temperature differential but the problem is that differential varies wildly in the coldest weather.

    I don't know what the low temps are in the Winter in Louisville  but I only ran into the really severe offsets last Winter when the air temps were holding in the single digits. The winter before was milder and on some of the coldest days I was using the wok. Just an sidebar comment: There is something a bit surreal about standing outside at night when it is -2 degrees and you are having trouble keeping the temps down at your wokSo if you don't get down that low where you are, you may not have seen the problem.

    When cooking indirect I usually let my Egg run for at least 30 minutes once it hits my desired temp and in real cold weather up to an hour. 
    Also a piece of meat cooked indirect is a lot more forgiving than baked goods.The other reason I have come to like measuring the grate temp is repeatability If something takes 2 hours with a grate temp of 375, then it should take that amount of time winter spring summer or fall. Yes I know assuming a similar sized piece of meat with similar fat content etc. But I don't need to even think about the temperature difference between the dome and the grate. For me the dome thermometer has become irrelevant.
    Website: www.grillinsmokin.net
    3 LBGE & More Eggcessories than I care to think about.