Help with HM and Keg? Dale/Andy


 
Tuning the pid setting wont do much if anything. I did a lot of smokes to tune it this close. Your fauxmado is ceramic and radiates a ton of heat at 700 to 800 degrees inside I can put my hand on the outside and it is barely warm to touch. Smaller fire is not how much charcoal or lump you add its how you control the combustion. I never put less than a full load of charcoal in mine. The problem with the Keg it is so well insulated you don't ever want it to over shoot, so easiest way is to approach the temp slowly. if it overshoots it does take a long time to cool as there is not a big ceramic heat sink to soak up and radiate the heat away for the smoker. mine holds withing 5 degrees on a 24 hour smoke once it is set by approaching the temp in two stages.
 
I used to use a stone but now only use it for pizza. Imo you don't need the added mass of the stone to hold or stabilize heat in the keg
 
My Fauxmado is dual shell insulated metal "egg" kinda like the keg just cheaper... but I can get it cranked up and still put my hand on the outer shell...
IDK how you can say PID tuning wont do much of anything, it does EVERYTHING! It controls how the HM reacts to the temp changes and setpoint. It seems your HM is not backing down from full throttle early enough to keep the fire in check, PID settings can help that by making the HM back down a bit bore it reaches the target temp. This way it doesn't stoke the fire so far that you have to choke it so long that it goes out. Remember that when using on at max only mode as soon as the HM backs down from 100% the blower turns off and the temps will bloom a bit, so it needs to start to react a little early to avoid a lot of overshoot. And getting the top vent set right is real important too, you might have to work out a startup vent setting and another setting after the food is in and the pit is stabilized.
 
After startup once the temp starts climbing, I close the vent down so it's open just a hair. The keg has a cast iron wheel on top with 6 openings, so a hair opening x6. Once they stabilize I open it a little more so it's not a stale smoke chamber.
 
I'm just curious what a "Keg" looks like. They must be insanely insulated much more than a BGE even. Can you share a link to some pictures?

My fan on my BGE can be off for 20 minutes and come back on and the fire is still going. There's plenty of leak air to keep it alive even with a rotodamper closing off the input and a new felt seal on the lid. I also have a big ole pizza stone I always use for my low-and-slows as a diffuser (and a place to hold a drip tray).
 
Bryan, here it is below. Started out as 'Bubba Keg/Big Steel Keg' in the US then was bought by Broil King here in Canada and changed to Broil King Keg. They are actually just up the street from me.

http://www.broilkingbbq.com/grills/keg

Double walled steel with insulation in between.

It looks like I finally have it figured out. Startup max 5% seems to be working. Hit the target with only 0.5deg overshoot. I had the regular max at 15%, and once it reached the target and dropped below, the 15% was too much and overshot 9 deg. I've backed that down to 10% now.
 
Last edited:
I'm thinking Dale is right, that his lump coal soaked up moisture sitting outside, 'cause the fire shouldn't go out that easily as long as there is an opening in the top vent it should stay alive for quite a while.
I've seen the Big Steel Keg cooker at an Ace Hardware, it looks like, well, a KEG (as in keg of beer)....
 
Mike Wallace said:
Bryan, here it is below. Started out as 'Bubba Keg/Big Steel Keg' in the US then was bought by Broil King here in Canada and changed to Broil King Keg. They are actually just up the street from me.

http://www.broilkingbbq.com/grills/keg

Double walled steel with insulation in between.

It looks like I finally have it figured out. Startup max 5% seems to be working. Hit the target with only 0.5deg overshoot. I had the regular max at 15%, and once it reached the target and dropped below, the 15% was too much and overshot 9 deg. I've backed that down to 10% now.
Click to expand...

So you're still not running the fan "On at Max Only"?
 
OK, yah, that's when the regular max would come into play...

I had lobbied Bryan in the past to change the fan "on at max only" mode to "on above XX%", reason being, the transition from no fan to fan running at max brings a fairly drastic change in air flow. The cooling effect from the rush of cool air combined with the rapid stoking of the pit can give you a dip in temp followed by a bump which will sometimes overshoot.

If we had a setting for "fan on above XX%", where the HM would ramp the fan speed from Min to Max between XX% and 100% the change in flow could be made much more gradual and likely prevent the HM from ever hitting 100%. For instance, set fan "on above 80%", at 80% the blower starts to add a trickle of flow, at 85% the fan is running at 25% of Max, at 90% the fan is running at 50% of Max, etc.

I think the addition of this feature would make things run a lot smoother over a wide variety of cook temps with less need to reconfigure the way the HM behaves for each, and make the HM configuration easier for a wider variety of pits. OK, off the feature request soap box! LOL
 
And as far as your choking situation, if you still have the problem when using fresh sorted lump then I would suggest you bone up on PID tuning. The PID settings can be tuned in such a way that it will back down from 100% as it approaches the setpoint, and so it will open up from 0% as it approaches the setpoint during overshoot. This will minimize overshoot by backing down from 100% a bit early to stop the active stoking of the fire by the blower, and minimize choking by letting a little air flow before the temp gets all the way back to the setpoint. If the keg is holding the heat so well it gets bottled up by the closed damper and lack of flow, meanwhile the fire is shrinking down smaller and smaller. When the damper opens the pit should cool pretty rapidly due to the inrush of cool air and smaller fire, which will help you settle on your target before you actually put the fire out.
 
Ralph,
Thought your rig was one of the ceramic copies of the egg. Does it have the hinged or removable bottom ash pan? It must really be constructed different from the keg, the keg hold heat so well a lot of guys don't like it cause it does take hours to recover from an overshoot on temp. As far as the PID maybe it could be adjusted better, with the settings Im using it does ramp down way before it hits temp, but again mine is air tight on the bottom only air comes from the rotodamper and any draft from wind though the top vent.

I'm pretty good at tuning PID controls as an PLC programing and startup engineer I tune PID's for many processes. Took quite a few brews, briskets and butts to get the PID dialed in where I have it.

When it goes up on the initial climb, it will overshoot really easy, even with the fan set low, Now I may try the fan at 5 percent may but afraid it would not recover late in the smoke when it may need a good puff of air to bring it back to temp. Once it heats up the inside the temperature of the metal in the keg acts to keep it stable since it is insulated. I never seen the air inrush drop the temp of my keg unless I had the fan at 100 percent and the fire was almost totally out from ash choking it. If it is not super windy it will hold temp plus or min 5. If the wind is really strong it will enter from the top vent and introduce enough oxygen to make the temp runaway then again the rotodamper is closed and the insulation wont let the temp drop. I normally run it with the top vent mostly closed, for the keg forum this seem pretty standard way to set the top vent even if just using natural draft to control the heat.

Hope he finds a better PID setting would love to try it, part of the fun of playing with the Heatermeter is the experimenting.

When I do an 18 hour smoke I will use less that a pound or so of lump.

Ralph what are your PID settings and how do you set your top vent. Would love to try them tomorrow doing a 12 pound pork shoulder.

I would also like to be able to adjust the fan on above XXX, would make it a lot smother.
 
Last edited:
Dale Ward said:
When I do an 18 hour smoke I will use less that a pound or so of lump.
Click to expand...

That's the part I love... I use very little coal as well...
I wasn't aware that Mike was using PID settings you had worked out for the keg grill, I thought he was just using stock values. It just seemed his settings weren't allowing the HM to back down early enough to avoid a long overshoot period. I have been experimenting with the RD3 for the past couple weeks so my PID settings are all over the place lately.
 
Put blower speed on startup at 8 percent then set at 225, had top vent at 1.5-2.
After put meat in temp dropped. At about 1 am adjusted vent to less than 1 about 3/4. set PID P 12, I .004 D at 6, left it for the night

ur7I80N.png
 
Glad to hear it worked out well with fresh lump coal... It can be a real PITA sometimes even with fresh coal when you get a bag that is full of all sorts of tiny pieces and powder, the fire needs to breath and the spaces between the coals help facilitate that....
 
You must log in or register to reply here.

 

Back
Top