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Smoke Tube Causing Excessvie Grill Grate Temperature Even At Lowest PID Temperature Setting

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    Smoke Tube Causing Excessvie Grill Grate Temperature Even At Lowest PID Temperature Setting

    Hi all.


    In these difficult times of COVID 19, I hope everyone is staying as safe and healthy as they can.

    My equipment is a Pit-Boss 1100 Pro Series upgraded with a Savannah Stoker PID controller, and an A-Maze-N 12 to 18 Inch Adjustable Pellet Tube that I fill to full with pellets.

    While I turn on my smoker and get it up to the PID set temperature of 275F, I light the end of the pellet tube and keep the flame going for 10 minutes as instructed. After 10 minutes (flame extinguished but tube is smoldering), I put the pellet tube on the top rack of the smoker, and let the smoker continue towards 275F. Once the smoker reaches 275F, I put my meat on, put the external thermometer's probe at grate level, close the lid, and set the PID temperature down to 225F.

    From having discovered Amazingribs.com 10 years ago, it's been instilled within me that the temperature at the grill grate is what matters, hence the external thermometer probe.

    At first, the grate temperature is around 250F, and then lowers slightly. But as time passes (another 15 to 20 minutes), the grate temperature shoots up way past 300F. At one time, the grate temperature probe read 350F.

    I turned down the set temperature on the PID controller, yet the grate temperature was still 300F. I even turned down the PID set temperature to the lowest setting, 150F, yet throughout the rest of the cook, the grate temperature stayed at 250F+.

    Before I bought and started using the smoke tube, the PID controller would be set to a temperature of 225F to 250F, and the external thermometer probe at grate level would register no more than 20F higher than the PID's set temperature throughout the cook. Now that I'm using the smoke tube, the grate temperature will always be 80F to 100F+ higher than the PID's set temperature.


    Can any of you brilliant fellow pitmasters please help me to troubleshoot this phenomenon of why the smoke tube is causing such a rise in grill grate temperature, especially since it is not resting on the grill grate but on the top rack?



    I will continue troubleshooting on my own and report back any findings, just in case my issue and research can help someone else.



    Take care.
    -Z

    #2
    All pellet cookers will govern temp based on their internal probe, a few newer models have a roaming thermocouple you can place on the intended coooking grate.

    Comment


      #3
      Something to ask, but when you were not using the smoke tube, were you also still using the stock Pit-Boss controller, or were you using this after market controller?

      I hate to say it, but to me, it sounds like a problem with either the controller, or the built in temperature probe. Unless you are putting the smoldering smoke tube right on the built in probe, it should not affect the smoker much at all. Not the way you are seeing. If you still have your Pit-boss controller, maybe you should switch it back in as a comparison. Or see if there is a way to test the built in temp probe. And finally, run without the smoke tube as a comparison.

      Comment


        #4
        I agree with jfmorris - it shouldn't be causing those swings, but I would put the tube at or below the level of the food. With it on the top grate your just blowing most of the smoke out the chimney. I have a 12" tube and used it a few times - didn't cause any temp swings, but I have a Rec Tec. Still, I didn't notice any change in the smoke profile and it was more of mess to clean up, so I stopped using it.

        Comment


          #5
          I have seen this exact thing in my smoker in the meat locker.. pid controllers don't like any other sort of heat..they do all sorts of computations and algorithms.. I don't understand any of it.. I have a smoke generator that runs at 500 degrees and it will throw the pid controller fits.. just remove the pid and put a dumb controller on it or get rid of the smoke tube.. I run my smoke generator the whole time my smoker is on and that makes it better but not perfect.. hope that helps

          Comment


          • Mr. Bones
            Mr. Bones commented
            Editing a comment
            Lol, reckon Alla my cookers have a 'Dumb Controller" lol!
            Last edited by Mr. Bones; April 22, 2020, 10:38 PM.

          • hogdog6
            hogdog6 commented
            Editing a comment
            Pit master or dumb controller? Same thing... huh... good to know. Haha😜
            I love it.

          #6
          Dump the tube. They really have never worked for me. Like others said, if you cook without it and the problem persists, then it may be the Stoker. Trial and error.

          Comment


            #7
            Hi all.


            Thank you for the valued responses. Soon, I will be performing a test with the external thermometer probe at grate level and the PID set to 225F. I will let the smoker go about an hour to see how close it holds to 225F. Then, for the next hour, I'll light the smoke tube and place it in the smoker to see how far it throws off the PID.

            mgaretz, I never thought of placing the smoke tube below the grill grate and rest it on the heat deflector. That should work very well. Is that what you did with your RecTec? Since you mention placing the smoke tube below the main grill grate and rest it on top of the heat delector, have you every tried placing a water pan there as well? Just wondering.


            Thank you all.


            Take care, and stay safe.
            -Z

            Comment


              #8
              zx11ninja something that you may not be aware of is that a PID controller typically produces less smoke than the non-PID controller you replaced. They control the temp so tightly (usually within 5 degrees of the set point) that less smoke is produced. The larger temp swings of the non-PID controllers tend to produce more smoke during the up-hill side of the oscillation around the set point.

              Grilla has an article on this:

              https://grillagrills.com/pid-controllers/

              Basically, they are acknowledging that their own dual mode controller will produce more smoke when run in the non-PID mode.

              Now, we all know that the location of the sensor in these pellet smokers is not always at grate level (I don't understand that!), so what the controller thinks the temperature is, and what the temp is at the main cooking grate, may be two different things. In theory, air circulation by the fan in a pellet smoker SHOULD even things out, but apparently that is not always the case, as most cookers have hot spots.

              Comment


                #9
                Hi all.


                I will be doing my testing on Friday, but I thought I 'd update my post with some useful information that I found. In the Savannah Stoker 4.5 Instruction Manual, page 8, section 7.3.5, this section describes "Pb Sensor Calibration Offset" functionality. With a range of +/- 50F, you can use this setting to calibrate the internal probe's temperature reading.

                Therefore, if you use a known good external thermometer probe at the grill grate level, and set the pellet grill to some temperature (say 225F), you can then use this calibration so that the built-in internal temperature probe's temperature more closely matches the temperature at the grill grate level. This should allow the PID to more closely track the grill grate temperature so that the displayed internal temperature matches the external thermometer probe's temperature. However, as ItsAllGoneToTheDogs has implied, the tracking would be better if the internal thermometer were positioned at grate level.

                I will keep you all posted.


                Take care.
                -David

                Comment


                • ItsAllGoneToTheDogs
                  ItsAllGoneToTheDogs commented
                  Editing a comment
                  TO be honest, I've found that as long as there aren't CRAZY variances, I'm happier not monitoring my grate temp. Probe the meat and let the grill do it's thing. I think that's why lots of people with box store pellet grills are happier than those of us with more expensive ones, because we're more likely to use additional monitoring devices which then drives us nuts Though obviously if only the pellet tube is the reason for variance, then that does beg investigation.

                #10
                Greetings gentlemen.


                First, I wanted to say thanks to you all for the assistance you have given me.

                I performed my testing over the weekend, and I found that the smoke tube was not the cause of my problems. As previously thought, I found that the cause is due to the location of the internal temperature probe. Let me explain further.

                The night before my test, I performed a boil test with my external thermometer probe and an addition thermometer probe. From 50F to the water's boiling at 212F, the external thermometer probe tracked the additional thermometer probe with no more than a 2F degree difference.

                On testing day, I set my Pit-Boss 1100 Pro Series to 225 and waited for the temperature to hit 225F as read by the internal temperature probe. However, my external thermometer probe at grate level read almost 300 F. I shut the grill down so that it could cool off.

                I started up my smoker a second time. As soon as the main fan turned on and the smoker started to build heat, I adjusted the PID controller. On the Savannah Stoker controller, I adjusted the calibration offset of the internal thermometer probe (Pb1) to +60, as the default setting of 0 was causing the internal temperature probe to report too low a temperature. After doing this, I raised the set temperature (SV) to 190. After 190 was reached, I increased the set temperature in increments of 10F and then 5F, while watching how closely the internal temperature probe was tracking my external temperature probe at grate level.

                Once my external temperature probe reached 225F, the internal temperature probe was still reading 10F too high. After more time to settle down, the internal temperature probe, my external temperature probe at grate level, and the set temperature all matched at 225F. This condition held for a few minutes. Mission accomplished.

                In summary, as ItsAllGoneToTheDogs has implied, the internal temperature probe should really be located at grate level and not half way up the left side of the smoker. Because the heat in a pellet smoker is coming from beneath the grates, the grates seem to always measure a significantly higher temperature than was is measured by the internal temperature probe mounted half way up the left wall. In my opinion, if the pellet smoker were designed so that the heat source (burn pot) were outside of the main chamber and offset to the left or right (like a stick burner's firebox), only hot air (convection) would be involved in the main chamber, and the temperature inside the main chamber would track more evenly regardless of location inside the chamber.

                When the opportunity and funds present themselves, I am going to acquire a second internal temperature probe, swap it with the original, and find an elegant way to mount it at grate level (perhaps the far back of the main grate) so that meat/drippings do not touch it and throw off the readings. I will report my findings back to this thread when that test is concluded.

                Thanks again gentlemen.


                Take care.
                -Z

                Comment

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