Stoker instability


 
J

Jim Smithson

TVWBB Fan
I have had some Stoker instability lately. The fan seems to delay its turn on for a few degrees under the temperature and so the temp drops more prior to shooting back up and overshooting.

Attached is a pic using Stokerlog. I am doing a 18hr shoulder right now and it is doing this again for the entire time but I cannot get my image capture to work for some reason.

05272008175847or4.png


anyone else? I have the sensors/fan directly connected to the stoker. I am using the stokerlog which I am not sure if that is affecting the control.
 
John, I used to have the same issue(my graphs looked exactly like yours); I now run with my old 14" clay saucer and the top vent 100% open, problem solved . . . in my case.
 
John,
Larry is exactly correct. The claypot base provides a great heat sink to stabilize the temp.

PS, Hey Larry how ya been?
 
thanks, I should have noted that I am using a clay saucer, no water. I run the vent 100% until it is close to temperature and then I reduce to at least 50% as it tended to overshoot if I didnt reduce it. I may have some leaks in the housing (around the door etc) that allows enough air that it overshoots.

but I am not sure if I have tried that since I ran the clay saucer.
 
Yea I'd look at those air leaks.

Bob, doing well, I'm doing 36 lbs of pork butt right now, will be doing 12 rack of spares tomorrow all for a graduation party we're throwing. Loving my Stoker since I got the "kinks" worked out. So I don't hijack Jim's post, check out my post under BBQ, it's called Cooking for 60 there are some pics of the cook there too.
 
I've had a similar experience. Best I can figure is that there was not enough fire in there. When the blower kicks in, some air bypasses the fire and is able to cool the smoker. It takes a long time for what little fire there is to get going hard enough to make up for the bypassed air. Then once you hit the target and the fan shuts off your temp overshoots as there is no longer any air being forced and cooling your smoker.
 
that is very possible as I only light the charcoal near the fan with a propane torch. It works very well and uses hardly any charcoal.

I am going to experiment with vent openings next time to check for stability.

If it is a little fire issue, then I am going to live with it as my charcoal life is amazing. My last pork shoulder cook was 18.5 hrs total and I never even went back outside after I closed the lid. I was even able to turn up the temp to 250 then 275 over the last 4 hrs. (first 14.5 at 220)
 
I used to see graphs like yours, it happened to me when I had air leaks and a not so great fire.

My stoker has some of the most stabile temps I have seen on the forums.
Low and Slow

High Temp

Things that have brought me stability.
<UL TYPE=SQUARE>
1) Claypot base
2) Make sure the door has a good seal. This was probably the most time consuming part of clean up other air leaks.
3) Load up the charcoal ring, light 20 coals in this chimney, and spread them across the top of the unlit.
4) The top vent stays open 100% all the time.
5) Low and slow the bottom vents stay closed. High temp I start with them 100% and close as required.
6) I put the meat on the smoker before it gets to temp. The meat helps prevent the overshoot.
[/list]
 
thanks for the comments.

a few more:

- I have the temp probes going in through the door...so there is a gap due to the thickness of the wire. I installed those grommets from Rock, but the temp probes dont fit through the holes!! The silicone ring at the wire/probe interface is too large and I would damage the probe if I installed it each time and I dont want to leave the probes in the WSM all the time when not in use.

What do you do with the probe wires?

Your graphs above show a very quick temp drop from the lid removal and a quick recovery. I dont have nearly that temp drop...maybe it matters where the probe is located.

I fill the ring, but for maximum coal life, I only light a few coals near the stoker fan vent...that allows me to run a 18-20hr cook without even touching the WSM! This small fire may account for the instability...heating an oven with a small strong fire vs. a larger weak fire? not sure.
 
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ken Brown:
Jim,

Do you light the fire on the top or on the bottom? </div></BLOCKQUOTE>

I lite a few coals on top of the pile in the area near the stoker fan vent.

I wonder how lighting a few in that area, and then pile some charcoal on....
 
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I installed those grommets from Rock, but the temp probes dont fit through the holes!! The silicone ring at the wire/probe interface is too large and I would damage the probe if I installed it each time and I dont want to leave the probes in the WSM all the time when not in use. </div></BLOCKQUOTE>

Jim, I think the door could be a big part of your problem. I push the silicone piece back from the temp probe onto the wire, feed it through the eyelet, then push it back up on the probe.
 
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by LarryR:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I installed those grommets from Rock, but the temp probes dont fit through the holes!! The silicone ring at the wire/probe interface is too large and I would damage the probe if I installed it each time and I dont want to leave the probes in the WSM all the time when not in use. </div></BLOCKQUOTE>

Jim, I think the door could be a big part of your problem. I push the silicone piece back from the temp probe onto the wire, feed it through the eyelet, then push it back up on the probe. </div></BLOCKQUOTE>

can you do that repeatedly without damaging the sensor?
 
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">can you do that repeatedly without damaging the sensor? </div></BLOCKQUOTE>

So far so good . . . knock on wood . . . I actually called Rock on this and this was their suggestion/recommendation.
 
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