Stoker Overshoot Probelm....could StokerLog manual fan control help?


 
Yep, I'm the same way. I had to convince the wife that this wasn't just a gadget for me. It was an important tool for good BBQ.
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It's hard to argue with Harry's success. Lots of other guys on the circuit use the same combo, too, so it can't be bad.

Lookin' fwd. to your report on how it works.

The weekend is here, so "Gentlemen, start your smokers."
 
I started an overnight cook last night a little after 10 pm. The Stoker brought the fire up to 250 very smoothly, and held it there for about two hours. Then I had a cycle of temperature swings with a maximum of 276 and minimum of 234 (6 major cycles, getting larger, then smaller). After this, the temp settled in again right around 250. I had another cycle of swings at about 7 am, smaller this time (from about 245 to 257). Seeing this, I looked at the fire and saw I was running somewhat low on fuel. I removed the center section of the WSM, moved all the burning coals to one side, and added some fuel. All of this caused the temp to drop, of course. But once I put everything back together, the Stoker brought the temp up to 250 and it remained very steady for about 40 minutes. It has now started to oscillate again, between about 243 and 257. I wonder if this may have something to do with the progression of the fire through the pile of charcoal. As the cook continues, it appears that the fuel closer to the Stoker is consumed more quickly. As the fire progresses further from the point where the air is introduced, might this increase the time it takes for an increase in air volume to result in a corresponding increase in temperature? If so, that could contribute to the "yo-yo" effect some of us are seeing. It would be interesting to see what effect, if any, might be achieved by a modification to direct the output of the Stoker fan underneath the charcoal bed, rather than at one side of it.
 
What kind of fuel are you guys burning? I could see where lump could cause inconsistant results on a low temp cook due to its irregular shape. I plan on using Kingsford Blue on my first Stoker cook next week. I wouldn't think temporary 20 deg swings would be a problem at all as long as it settled down. It's the 50 deg swing that causes the fire to almost go out that would be a problem. Dan
 
I've had temp swing/overshoot issues when using large pieces of smoke wood, when using fist size chunks never a problem.
 
Interesting comment about the fuel type. I've been using Royal Oak natural and Kingsford competition. Both burn hot and fast. I'll try some reg. Kingsford this w/e.

I have a spare charcoal grate that I can use to raise the fire up so that the fan blows under it. I'll just put a brick on the existing grate and add the second grate on top of that.

It should be interesting.
 
Using reg. Kingsford charcoal seems to cure my instability problems. What charcoal are you guys using?

I suspect that the problem with natural charcoal is because natural stuff burns hotter but doesn't necessarily burn as steady at low temps as reg. charcoal.

Now my WSM and Stoker work perfectly. I'm 2.5 hours into a test cook at 245, and I've opened the lid twice. Each time the Stoker brings temp back in line within a few minutes. The fan pulses are evenly spaced and their duration is short - the same as what I see on my Klose.

Temp is a flat line with the top vent open about 1/3. I'm lovin' this. I did not test out raising the fire above the fan as I indicated in my earlier post - no need to.
 
Final Observation: As the charcoal burns down and the coals get spread out, the temp begins to oscillate. This occurred after 3 hours of cook time with the amt. of charcoal I used.

I pulled the middle section of the smoker off and piled the coals together near the fan. Temp oscillations ceased. It burned for another 3 hours w/o any temp change.

This would support Larry D's observation that the fire getting spread out is a major source of temp variation. In fact, it may have more to do with the oscillations than the type of charcoal. I haven't tested that theory. As an old college text of mine once read, "That experiment is left as an exercise for the reader" to measure the significance of charcoal type on temp variations.

I hope this helps.
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First Stoker use today with my 22.5 WSM. It worked great with the WSM. I did a 6# Butt and 4 baby back ribs. 11 hours with a full bag of Kingsford blue using minion method with 3/4 chimney lit on top. The Stoker held 230 +/- 2 degrees for 8 hours, mostly within +/-1 degree. At the 8 hour point it started +/- 5 degrees so I stirred the coals and it went back to +/- 2 degrees for another 1 1/2 hour then back to the +/- 5 degrees. At this point I added a few more coals and temp still stayed 230 +/- 5 degrees. I think +/- 5 degrees is excellent it is just after so many hours of +/- 1 degree it really stands out when it swings more. Used the 5 minute fan off feature at all lid removals and temp restabilized within minutes. This thing is great! 7 of us for dinner and Wife said it was the best yet! The lid thermometer I had always used before read 25 degrees less than rack temp on Stoker so I had previously been cooking 25 degrees high. Very happy after first cook. By the way it is a 10 CFM fan and I had top vent 1/2 open. Dan
 
Hello all,

I started this thread because I have had some overshoot/undershoot problems with my Stoker. I do use lump, which could be the main reason for the swings, but I also had 3 cooks using lump that didn't cause big swings either. So I wanted to see if anyone else was experiencing it. I do think the logic in the Stoker could be improved by evaluating the delta between the set and actual temps to do more of incremental pulse of the fan initially to bring the temp up or down, then the longer the delta stays a certain amount without decreasing, then it can increase the pulse durations. But that is just my observation and I am by no means an expert in software dev or control systems.

Anyway, I have started ramping up (or ramping down) my temps to my initial setpoint and it is much better. It does take about 15-30 min to do this, but the results have been good. The other time when you have to watch for the swings is when you open the lid. I have been doing as Amir said and turning off the Stoker before I open the lid, which helps. Also, if I know I will need to have the lid off for some time, like foiling or accessing the bottom rack, then I remove the entire mid section off the bottom bowl and put the lid over the bottom bowl. This keeps temps in check and lets me take as much time as needed for the food. Then I assemble the WSM again, turn the Stoker on, and watch the swings. If I get a big overshoot, then I raise the temp setpoint, to have the fan turn off when it hits that elevated setpoint, let the temp drop stabilize a little, then lower the temp setpoint some more and repeat until I get to my desired temp again.

I love my Stoker and Stokerlog though and would not go back to smoking without them. I also just changed my WSM mount to a guru type mount and will see if that makes a difference in the swings since it seems to disperse the air better in the charcoal bowl than the dog bowl setup.

Thanks for all of the replies and info. I hope my info has helped some as well.
Kg
 
Dan F: My lid temp is about 30* lower as well compared to my grate and that is with a Tel Tru in the lid, so there is a big difference in the temps.

Glad your first cook went well. I will be getting a 22 WSM in a few months after we move into our new home and I have room on my patio.

Good luck,
Kg
 
For temp swings you can also use sand instead of water in the water pan, a few fire bricks work well under the pan too. Anything to hold heat.
 
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