Cold weather grid/dome differential

itsmce · November 2014

Yesterday's cook was a pork butt, turbo...I think.

It was in the 30's all day. I was shooting to cook the butt at 350. I used a Maverick to monitor the grid temperature. I kept an eye on the dome temp too and was surprised to discover that the dome temp was 70 to 100 degrees lower throughout the cook. Is it normal to have SUCH a difference between the dome and grid in cold weather?
It took 7 hours to get the 6.7# butt to an internal temp of 201. Grid temps ranged from 340-410. Dome was between 290 and 315. Late in the cook I moved the grid probe to the upper grid...so it would be closer to the dome thermometer. In that position, the temp was only 20 degrees different.
The butt was directly on the grate on the platesetter, legs up, which held a drip pan on foil ball spacers.
I need to get this figured out before Thanksgiving.

cottonseed · November 2014

I believe that's pretty normal. I noticed the difference a couple nights ago when smokin a shoulder. At the end of my cook the grid temp was 325 and dome was 250 I had the exact setup except a 10lb but. We had temps in the the low 30s.

theyolksonyou · November 2014

I just go with the probe temp and don't worry about it, there's always a difference and it is different depending on the setup. When's the last time you calibrated the dome thermometer.

Carolina Q · November 2014

A man with a watch knows what time it is. A man with two watches is never sure.

I have had my egg for 5+ years and have never checked my grid temp. Don't know, don't care. Dome temp only... just like in my oven.

Check your calibration on the dome thermo.

gerhardk · November 2014

I cook year round and I agree the dome temp will be lower for the first hour or so after putting the meat on but after that the dome temperature will rise above the grid temperature. Where was the probe on the grid? If it is exposed to any direct heat or the convection flow you will read high for the grid.

Just my 2 ¢

Gerhard

SmokyBear · November 2014

I just had this EXACT thing happen last night, cooking the "test Gobbler" (Spatchcock) for Thanksgiving.

Got temp to 400 solid (45+ min from lighting to stable). Added 12 lb Gobbler, with a Maverick probe sitting on top of the bird (vs being on the grid).

Dome temp kept reading 50 - 70 degrees LESS than probe temp for the 80 minute or so cook (350'ish dome, 420+ probe).

What's REALLY weird is that I opened the DFMT a few times to increase dome temp. (I'd been running with "holes open" and instead swung the entire top open a bit). Dome then (predictably) shot to around 400, which is where I wanted it - but probe temp DECREASED a bunch (WTF?!)

I first thought that the cold air rushing in dropped the temp of the probe sitting on top of the Turkey, but that same cold air "should" have also decreased the temp of the dome thermometer.

Very weird.

Gobbler was good - 2nd Maverick (food) probe in the breast said 174 when I pulled it, and it was still very juicy. Skin didn't crisp nearly as well as my Spatchcock Chicks do though, which I "think" is because the dome was only at 350 - and I've found Spatch Chick needs closer to 425 dome temp.

I don't normally cook with the Maverick and only did this because I didn't want to destroy a 12 lb Spatchcock Turkey by overcooking it.

All a learning experience, but also very strange.

ETA: Dome thermometer is calibrated, so I don't think that's it.

dldawes1 · November 2014

Where was your grid probe located ?? Close to food, near the rear of the egg where heat flow is hotter ??

I just cooked a deer ham, and my grid temp stayed about 40 degrees below my dome for 6 hours...both steady.

Lots of variables to make them different.

bodski · November 2014

I've only used a probe on the grid a few times - all have been indirect and generally low and slows. My experience has been the opposite; the dome was higher than the grid temp. In all cases I was using a plate setter, so there was no direct heat from the fire. I can't recall what the outside temperature was, though.

itsmce · November 2014

To follow up on my original post:

My grid probe, I think, was on a part of the grid not protected by the platesetter. This could have impacted things a bit I suppose. I calibrated my dome temp gauge yesterday and did find that it was reading about 15 degrees low, so I guess my temperature differential wasn't as big as I had suspected, but still 60 or more degrees. While I had my pot of boiling water going, I tossed in the BBQ probe from the Maverick set. It read 212. Gotta love accuracy.

thegooddocta · November 2014

Did you have your daisy wheel on? Wondering if that might influence things... I'm planning to set temp with the daisy wheel on turkey day (I don't usually use it, and totally control temp from the bottom) because I feel like it might help with heat loss. Totally gut right now, but will test this weekend.

SmokyBear · November 2014

If it helps..

I had the Maverick probe ON the Turkey thinking I wanted to measure "air around the Turkey" temp..

In my case, a 70+ degree difference with the dome temp is even MORE weird since it's in the same general area, and there was a HONKIN Turkey blocking the probe from direct heat.

Don't use the Maverick much but would think there's a big difference between grate and dome temp.

bodski · November 2014

If you had a plate setter on, but had the probe over an area not protected by the plate setter, you probably had an exaggerated grid temp. There's a lot of heat being forced to the outside of the plate setter.

SmokyBear · November 2014

I did raised direct, so no platesetter or anything else (other than a honkin Spatch Turkey) in the way.

Very weird the big (70 degree) temp difference between dome and top of turkey (with the Maverick grate prob sitting on top of the bird).

stemc33 · November 2014

@itsmce‌, Last week was my first time using my iGrill 2. I only did a spatchcock, but my grid&dome evened out quickly. Outside temp was -4°. I don't know exact time it evened out(guessing 15minutes) and I know a chicken isn't the same a butt. Like you mentioned, it was probably probe placement.

dldawes1 · November 2014

@ itsmce....I thought it sounded like you had direct heat on the probe. I usually try to position it over one of the legs of the PS and at least a couple inches from the food. Low temp food will also throw off a grid temp probe's reading.

I use the Maverick remote and have never had a problem with it. I onlty calibrated my BGE dial probe once when I bought the egg in Dec 2013 ( it was off about 8*) and again around june or july. It was OK when I rechecked it the 2nd time.

Just my eggsperience,

Donnie

dldawes1 · November 2014

@SMOKYBEAR...maybe the probe was too close to the turkey causing a low reading from the colder bird temp. I have seen that happen when I impatiently place the probe too close.

SmokyBear · November 2014

@dldawes1 - thanks..the probe resting on the turkey was actually HIGHER than the dome temp by about 60-70 degrees, though (very weird).

Cold weather grid/dome differential

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