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Alpharetta_EggHead

Can you trust the grill thermometer?

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Newbie here, with a newbie question. I recently purchased a XL Big Green Egg (used). When I did my first cook, I used my ThermoWorks Smoke thermometer for ribs. For most of the first couple of hours, there was a 30+ degree difference with my probe thermometer. For instance, my Smoke said it was 275, but the thermometer on the grill said 240, although both of them ended up being the same. But they weren't the same in the beginning, and I think there's a big difference between 30+ degrees in the opening hours of smoking BBQ ribs.

 

(1) So who do you trust?

 

Also, this is a related question: How much charcoal would you advise putting down for a BGE? I know they say to fill it up to the rim, but that seems a little wasteful when I'm only cooking a few chicken breasts on an XL. However, I could be wrong there, meaning that perhaps the charcoal operates more efficiently when at full power. (2) Thoughts? 

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This is the most common 'issue' people run into when using electronic thermometers in an charcoal grill or smoker.  I am a FIRM believer in using the dome thermometer for cooking.  I have never had a failed cook when using the dome thermometer.  You will also not likely ever get the dome and the grate temp to read the same thing.  It might even out after a few hours of cooking without opening the lid.

 

I trust my dome thermometer BEFORE trusting the electronic probe on the grate.  There a several issues that will cause your grate thermometer to be off.  

 

1 - if it's too close to the meat it will experience a cooling effect.

 

2 - if it's too close to the outer edge where hot air is coming up from around the heat deflector, it will read hotter.

 

In reality, you need your grate level probe to be at least 2" away from the meat and at least 2 or 3" inside from the outer edge of not more before it will give you an accurate reading.

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Best thing to do is pick a thermometer and stick to it. Lots of folks here use the grill. As for lump fill er up! Ceramics are good at putting its self out after being closed up. I have found that if i am doing a small cook chicken boobs or thin pork chops i put in less lump. Its something you have to experiment with. Anything that is low and slow load it up to the top. You will be surprised how much is left after a 10-12 cook. Best of luck!

 

 

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A simple answer, IMO,  is "Trust Both". It is completely normal to have a 30 or 40 degree discrepancy between a grill located thermometer and your dome thermometer. There is a lot of ceramic surrounding the air in your dome. The air temp will rise as the ceramic in your dome and kettle "heat sink" and come up to temp.As that happens your dome thermometer will show a rise in temp and eventually match your grill temp pretty closely but often not exactly depending on where you located your grill thermometer. It can't be too close to what your cooking, any vessel or pan, or the edge of your deflector where it will catch the heat rise up the wall of your kamado. However, every time you open the dome you mix the warm inner air with the ambient temp air  outside your kamado, and the temp will drop and then slowly rise again as the all the air inside your dome comes up to temp. The amount of charcoal in you fire box has nothing to do with your temp. Temp is controlled by the size of your fire, which is controlled by the amount of air you feed it. A funny personal story, is that once when cooking a turkey, I actually think it was my first one. After I put the bird in, I glanced at my thermometers and the grill showed 350 while the dome showed 37. I'm thinking WTH, and checked my vents opened the dome and looked inside, no issues. Closed the dome, same thing. Opened the dome again and saw a small round hole in the turkeys breast where my dome thermometer shaft pierced it. I had a good laugh. And learned a good trick. When your cooking a turkey or big cut, take a wine cork and drill a hole through it end to end. (the hole needs to be big enough for the shaft or your dome thermo to easily slide through) Then pull your dome thermometer out and slide it through the cork and push it back Into the dome with the cork as a spacer outside the dome. The length of your thermo shaft inside the kamado is shortened and the turkey will not be pierced. Regarding the amount of lump,  a full load of lump up to the rim insures that you have enough for any type of cook you want to preform. If you put in a short load and light a big fire you will achieve  high temps but for a short time until the fuel is consumed.  I always run with a full load. I found out early on cooking pizza (considered a short cook) that you can  run out of lump during a high heat cook as well as during a long low and slow cook. I was doing multiple pies for a gathering and after about 10  my temp started to drop from my normal pizza cooking temp at 650. cooking with a full load is not  wasteful as charcoal can be reused as long as there is some carbonized wood left. Just shake out the ash and top off your once burnt lump with fresh lump and your good to go again and again. Happy cooking, and by the way, I too cook on an EGG, mines a large. Great grill you purchased. 

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I had this same question long ago. -got some great answers from the forum. @John Setzler had some info that dispelled any thoughts I had to not trust my dome temp gauge. I have proved over and over to myself that using dome temp itself is OK.

 

I imagine your Egg has a great OEM thermometer.

 

Some  OEM grill thermometers could have faults. So always do a calibration confidence check to see that your OEM thermometer is accurate.

 

Electronic temp sensors are great and usually are spot on accurate within a couple of degrees. Bear in mind that an electronic sensor and an analog style OEM temp sensor are constructed differently, and placement matters, but will both give accurate readouts. @keeperovdeflame provides excellent info above. 

 

Glad to have you.

 

 

M.

 

 

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6 hours ago, John Setzler said:

I have never had a failed cook when using the dome thermometer. 

 

That's a strong, strong, strong statement.

 

6 hours ago, John Setzler said:

In reality, you need your grate level probe to be at least 2" away from the meat and at least 2 or 3" inside from the outer edge of not more before it will give you an accurate reading.

 

I honestly believe that's the issue. I've been keeping my ThermoWorks Smoke thermometer about 1 inch away from the meat, while also located about 1 inch from the edge. Now I will try to clear out a spot closer to the inside. Thanks for your help!

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Dome thermometers have been guesswork for me, up to now.  When I added a DigiQ to my Akorn I had anywhere from zero to 40 degree differences between the analog and the digital, so I trusted the DigiQ.  Buying a Joe, the dome thermometer has that little screw in the back that lets you calibrate it in boiling water for a known temp.  Suddenly analog and digital started to agree with each other.  So now I have a dome thermometer I'm starting to depend on.  If more manufacturers started building in the ability to calibrate their dome thermometers, we would probably start seeing less crappy thermometers.

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My Akorn done thermometer is verified accurate, and the KJ, I assumed would be as well (no issues in use). The big differences I found are the length of the probe and the speed of response. The Akorn is slow, and its probe is too short, so it reads too close to the lid. Add the need to index a deflector leg under it and there's a lot of room for variation in the Akorn. 

 

I came from a 2-barrel smoker, where I learned to control exit temperature. That's served me well in both Akorn and Big Joe; the top vent is your control point. It's unaffected by food and gives you a good estimate of fire size. Highly recommended.

 

In the Big Joe, the dome thermometer usually agrees with the exit vent temperature when equilibrated, so I'm with John based on the data I've seen... You only need the dome thermometer, but I like having a remote!

 

Have fun,

Frank 

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16 hours ago, keeperovdeflame said:

 I had a good laugh. And learned a good trick. When your cooking a turkey or big cut, take a wine cork and drill a hole through it end to end. (the hole needs to be big enough for the shaft or your dome thermo to easily slide through) Then pull your dome thermometer out and slide it through the cork and push it back Into the dome with the cork as a spacer outside the dome. The length of your thermo shaft inside the kamado is shortened and the turkey will not be pierced. 

 

Thanks for taking the time to write all of this out. And I haven't smoked a turkey yet, but I will definitely use this trick. Thanks for sharing.

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A couple months ago while doing a rib cook I did a little thermo test. Basically, I had checked both the grate probe and meat probe of the Themoworks Smoke in boiling water. Both came up within .2 degrees of each other. Then checked the dome thermometer and it was way, way off in left field. During the cook I decided to use the meat probe (I don't use it when cooking ribs) to measure dome temp near the dome thermometer to compare readings. This cook was 6 racks on a 22" Pit Boss using 3 layers of racks to fit them all in. Grate probe on middle rack and meat probe inserted through top vent to put it within about 1" of the dome thermometer. While the two Smoke probes never got more than 8 degrees from each other the dome thermo was easily 85 degrees off. Granted, this is a cheap Pit Boss thermometer and it seems to work just fine for higher temp grilling but I would never trust it for low and slow. Here's photos of the set up:

 

IMG_2771.JPG

IMG_2772.JPG

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Are some meat probes straight? Mine all have a 90° bend, so when I push it through the top vent, teh tip is in danger of hitting/toughing the sides of the dome.

 

How do you get around that? In the photo above is that 90° angle outside the top vent...is that what I'm seeing in the photo?

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I would trust the thermoworks smoke over the bi-metal dome thermometer any day of the week. Those thermometers that come in most cookers are not accurate, and if they are its usually an accident. (I say this because I also have a Weber smokey mountain, to which everyone will say you cant trust the dome thermometer, somehow mine is dead accurate.)

The easy test is to stick the probe of your thermoworks in a pot of boiling water. It should read 212 F. If it does, its accurate. 
A 40 Degree difference between the grate and the dome would need to be accounted by something. Either the probe is touching meat, possibly you have moisture in the probe port, perhaps a defective probe. 

However,
 

Quote

For instance, my Smoke said it was 275, but the thermometer on the grill said 240, although both of them ended up being the same. But they weren't the same in the beginning, and I think there's a big difference between 30+ degrees in the opening hours of smoking BBQ ribs.


To me there's not enough information to answer this. How long did it exhibit a 30 degree difference? It wouldn't be abnormal in the first hour maybe, especially if its cold weather. But if you were running it for 5 hours and found a 30 degree discrepancy between the dome and grate I'd say one of them for sure is reading wrong.  Where you place the probe can also make a difference, exhaust vs grate for example. 

 

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