Temp Variance - Normal?

Discussion in 'Propane Smokers' started by meanfish, Dec 28, 2007.

  1. Hi All,

    Not sure if this or the thermometer forum is the proper place for this, so if I'm wrong, feel free to move me.

    I've got a BBQ Grillware Vertical from Lowes and I did the first part of seasoning it last night (brought it to 350°F, or so I thought, and held it there for 2 hours). The last part of the burn, I put my digital temp probe (Accu-rite from Wally World) in the top part of the smoke chamber, close to the door thermo.

    Here's my problem. The thermo. on the door had read constant 350°F for over an hour, and quickly returned to that after I opened/closed the door to insert the probe. The digital probe, on the other hand, quickly maxed to 392°F, and probably would have registered higher if it could've. The digital probe is brand new, so it's not tested or calibrated, and the door thermo. on the smoker has a tendancy to read about 15°F low according to other posts on here, but I've got a 40°+ variance! [​IMG]

    Any ideas on what I need to do to figure out which thermo. (if either) is correct and to get a more accurate read on what's going on in my smoker? I'm thinking of heading to Academy and picking up a couple of Old Smokey BT-1's and doing a dual thermo. mod (upper and lower). Would that leave me in any better shape than where I am now, or would I just have two inaccurate thermo's on my door instead of one? [​IMG]

    Thanks for the help!
  2. emtee

    emtee Fire Starter

    I think that I would calbrate the digital thermo first. Stick it in boiling water and adjust for your altitude. Should be about 212F @ sea level. At least you'd know which one was off the worst and which way to go first.

    Yet another $000,000,000.02
  3. glued2it

    glued2it Master of the Pit

    You can test your thermo with boiling water. At sea level water boils 212º (if I'm not mistaken)

    I guess I was a little slow on that one!

  4. Sometimes it's hard to think of the obvious when you're frustrated. [​IMG]

    FYI, you can calculate the pressure-corrected boiling point of water for your location here: http://www.csgnetwork.com/prescorh2oboilcalc.html

    I used the barometric pressure from weather.gov. I'll report back what I figure out after work today. Thanks for the help!
  5. fatback joe

    fatback joe Master of the Pit OTBS Member

    I don't have experience with your particular smoker, but I know that most of the stock thermometers on the store bought smokers are notoriously crappy........and even if they are accurate, they are often located in the wrong location to be much help. You can try calibrating it if possible, but I personally would not spend a lot of time messing with it. Try clipping your digital probe to the one in the door and see how close they are. You might find that it is accurate and the difference between the two was just due to being in different locations.

    Nice things about the probes is you can put them right where you need to know the temperature.......on the grate where your food is cooking.

    The thought of having an upper and lower mounted therm is good IMO. If nothing else, it will give you an idea on the difference between the upper and lower part and also give you something to lean on if your digital ever croaks at an inconvenient time.
  6. meowey

    meowey Master of the Pit OTBS Member SMF Premier Member

    As mentioned above, I would be suspicious of the stock thermo. In my GOSM, there is about a 20° difference between the top and bottom of the unit as measured by digital probes. I try to have one at the level of the food.

    Hope this helps!

    Take care, have fun, and do good!


  7. oillogger

    oillogger Meat Mopper OTBS Member

    When your smoking + or - 15F in your smoker thermometer readings is nothing to worry about but I would be concerned with a difference of 40F. The dial thermometers tend to be not as accurate as the digital probe thermometer since the dial has mechanical components. When calibrated with boiling water a dial thermometer will usually do just fine for smoking. It will be calibrated around 212F or a little less which is close to magical 225F that smokers like thus being more accurate there than at the higher temps of 350F where larger differences are less meaningful to the smoker. I think putting two digital probes in other spots of your smoker is great to understand where your hot and cold spots are but once the characteristics of your smoker has been determine that is no longer necessary. Another indirect way of doing this would be to load up every rack with chicken pieces and note ones are the most dry and which ones are the less cooked after a smoke. This will help you determine the general pattern of the heat in your smoker and adjust the way you load your smoker that will produce the best results. I find that my Big Block will generally be hotter around the sides of the lower levels since the water tray is in the bottom middle just over the burner. The upper levels will have more even heating. Because of this I will load my smoker as high as possible for more even heat and smoke. Remember that when your smoking that most things are relative and not percise.
  8. ron50

    ron50 Master of the Pit OTBS Member SMF Premier Member

    I have a CCSV vertical gas unit and there is always a variation between the stock thermometer and my digital Maerick ET 73. Both are tested and accurate.

    Most smokers will vary according to things like, how fully loaded it is, what shelf the therm is on, is it near the wall or towards the middle of the shelf, etc.

    I try to put my digital thermometer near the meat without touching it.

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