Wild Temperature Swings in DBS

[TimE916]

Hi all,

I've been using the Digital Bradley 4 rack for about 9 months now.  I have pretty good luck overall,  but lately I've been having inconsistent smoking times - generally much longer than expected.  For example, I'm smoking a 6 lb pork butt today, I've been smoking it since about 9:00 AM, it's now 5:30 PM - so 8-1/2 hours, and I'm still at about 160 Internal Meat Temp.  It has been in the mid-60's with no wind, and it's sitting on a table on my patio in the direct sun.
I just purchased the new Maverick wireless, so I can now monitor the temp of the smoker as well as the food.  I was surprised to see large and fast temperature swings in the smoker.  I set it for 225, and I've seen it swing up to as high as 265, and as low as 180 according to the Maverick.  On the other hand the display on the smoke generator shows it fairly steady, going between 200 to 235.  I'm suspecting something isn't quite right here...  ???
I've read all about using a PID etc... but frankly after dropping so much on the smoker, I would have expected a little better temp control.  I'm not too excited about dropping more money on a PID...  What I am hoping is maybe some input on some things to check.  My gasket appears to be intact - at least I don't see any smoke leaking out anywere.
Anybody have some other ideas?  Do I need to be reaching out to tech support?  Is there something I should be cleaning?  Or NOT cleaning?
Any help would be VERY appreciated!

I'm getting hungry!

[GusRobin]

temp swings are pretty normal for the DBS. Same with your kitchen oven. Sometime set your oven for 300 and put the maverick in there and you will see some big swings.
As far as the timimg on the butt, it is about normal. I have cooked 8 lb butts at 225 (with a PID)that have taken 16-22 hours -- all depends on the butt. So 8 1/2 hours to 160 for a 6 lb er is not abnormal or the result of a defective smoker. How long has it been at 160? Usually it "stalls" around that temp for a couple of hours. At around that temp the collagen is melting and making it tender but cooling off the meat as it melts. You will be tempted to turn up the heat but I would not recommend it. You probably are looking at least a 10-12 hour cook plus an hour or so if you FTC.

[mjdeez]

Is your V-tray positioned so it is like a V and not like a /\ ?  Should be like a V.  If incorrect it will cause a lot of problems, the worst of which is a fire.

[TimE916]

Thanks for the replies.
GusRobin I guess I wasn't expecting to see such wide swings.  80 degrees is a lot of variance!  Maybe it's always done that but now that I ' aware of it, it seems like a bigger deal than it its.

I'm of course familiar with the plateau, but I never understood why the temp stalls like that.  Thanks for the explanation!  That makes a lot of sense.  I never thought that the rendering collagen would carry the heat out with it as it melts, but that explains it I think.  It sat at 161 for about 3 hours, and now is beginning to creep up.  It's 8:30 PM and I'm now at 176 - so it's beginning to climb again, but ever so slowly.  Looks like a late bedtime for daddy tonight  :-\

I'm hoping for about midnight now.  If that holds true it will be a 15 hour smoke.  Other forums have said to allow somewhere around 1-1/2 hours per pound, so I was assuming with a little fudge factor that it would be getting close by about 7:00. 
Now that it's well into the evening, it has cooled off quite a bit, so to compensate I've adjusted the temp up 10 degrees to 235.

I can't help but wonder if a coal smoker like the Big Green Egg might provide a little better control - which sounds crazy since I have this great digital controller...

mjdeez, yes my v pan is correctly positioned.  Thanks for the suggestion.

[GusRobin]

If you are measuring the swings with the maverick it could also be a case of the meat drippings landing on the probeand you are getting false readings.

[mjdeez]

80* is excessive. I did a Canadian bacon today at 200*F in a 6 rack DBS.  I didn't pay too close attention to the temperature reading on the DBS, but my Maverick said it was getting down to around 170 and up to 215, in partial sun. 55*F outside temp, minimal wind. Vent 3/4 open. Open the door as little as possible.

One other thing you might try is one or two foil wrapped bricks, preheated to the set temperature, and placed on the bottom around the water bowl or above the meat. This will help stabilize the cabinet temp, but if I were you I'd still try and track down why the wide swings.  Someone else on the forums may have some other ideas, and yeah tech support is a good idea too.

[RAF128]

The temp swings you report are higher than what I've seen in my 6 rack but to me 25 degrees was too much.    Also I noticed everything took longer to cook than I was used too.   I hung a temp probe in the cabinet and notice that the cabinet temp was lower than what the DBS showed.   IMO that's because the sensor in in the back wall right about the heating element.   When I allowed for the difference in cabinet temp when setting the DBS temp cooking time were closer to normal.    I cured the whole problem with a PID.

[Keymaster]

I finally got a PID and Maverick 732 Last week for the exact reasons you stated above and itchen to try them both on my BDS-6 :)

[TimE916]

Thanks again everyone that took the time to reply.

I finally finished smoking the pork butt about 12:30AM.  So, all in, 15-1/2 hours to smoke a 6 pounder.  I pulled it out at about 190 IT as I just kinda ran out of patience.  It turned out great!  It fed 6 hungry mouths Sunday evening, with lots of oohs and ahhs.  I certainly can't complain about the results using the Bradley that's for sure.  Proof in the pudding and all that.

After thinking this through a little bit, I think positioning of the thermometer is key to this whole thing.  When I initially placed the sensor, I put it about 1 inch off the back and left walls, on the same rack as the meat which is where the built in oven sensor is positioned.  I think that is too close to the heating element, and when it turned on, that heat just blasted away at the sensor.  So, I moved it away - closer to the door and a little more centered on rack.  That reduced the temperature swings somewhat.  Next time I'm going to move it so it is more centered on the door, and probably on a different rack than the meat.  In theory by moving it further away from the heat source, I'll maybe get a slightly better "average" temp.

Thinking about this a little more (I try to avoid it, but it happens sometimes) I have to assume that the heating element isn't like a rheostat where you actually control the temp of the element, but instead it is more "digital" - meaning it is either all the way off or all the way on, and the cabinet sensor tells the controller whether more heat is needed or not...  Can anyone confirm that idea?  If that's the case, then that would further explain the big swings in temperature...

[mjdeez]

Thinking about this a little more (I try to avoid it, but it happens sometimes) I have to assume that the heating element isn't like a rheostat where you actually control the temp of the element, but instead it is more "digital" - meaning it is either all the way off or all the way on, and the cabinet sensor tells the controller whether more heat is needed or not...  Can anyone confirm that idea?  If that's the case, then that would further explain the big swings in temperature...

This is correct. I have confirmed on mine that the heating element remains on until the sensed temperature reaches the setpoint. Then it turns off until it reaches the setpoint-10*F. Then it turns back on, and repeats.   I've never tried to figure out if the hysteresis (delta temperature between on and off) is the same if I have it set to Celcius.

[Headcheese]

I'm bumping this thread.  I just received my 4 Rack DBS on Wednesday, seasoned it yesterday and starting smoking today.  I started with some Baby Backs.

I was concerned about the speed they cooked at.  I set it to 220F and it seemed they cooked way too fast.  I don't have a Digital Cord type thermometer but I do have a pretty good Digital Meat Thermometer from CDN.  I dropped that into the vent.  I was surprised to see how much temperature variation as well.  It would shoot up as much as 40F above the set point.  The Digital Temp on the Smoke Generator was reading much lower.  It has a considerable amount of lag.  What I'm curious about is whether this lag is in the Controller or the Thermistor mounted in the back of the oven.

I'm now thinking about Modding it with a fast response sensor.  I'll just need to figure out the specs on the existing unit.