PID Tuning for Chargriller Akorn


 
J

Jason G

New member
I was wondering if anyone could give me advice on a "baseline" PID settings for the chargriller AKORN. I realize I'm going to have to learn a little bit here, and get comfortable PID tuning on my AKORN, but I'm sure there are other AKORN owner's here that have been down this road already I was wondering if you good give me your thoughts on what my "default" settings should be, at least to start off.

I just used the default HM PID settings yesterday, and in servo mode (using Tom Kole's offset rotary damper, thanks Tom) with fan assist, for a 3 hour trial burn and here's were my results:

27xidrq.jpg


I had a crazy overshoot in the beginning but I think that was on me because I couldn't get my pit probe to read on the HM (that 732 connector length issue), and I had it in fan mode @ 100%. Once i got the pit probe reading I was already at 190, so I can imagine it was coming up too quick already. So I took the set temp up to 300 as that was the range i was in based on the overshoot. Then I had to play with the top vent a bit, to find that sweet spot. I settled in on a tiny gap the same size as the allen wrench i used for the HM housing.

The HM tried to do it's thing, but you could see the temp was very slow to respond at the upper and lower limits, with 30 degrees (+/-15) of oscillation. Even when I dropped the set point to 275, the temp fell to 250 instead of holding at 275.

Any advice would be appreciated.

 
It's hard to say exactly what's going on from that graph. Can you post exactly what your settings were? It looks like you stoked a pretty big fire. For low and slow, you just want to light a few coals and then let the HM take over. From your video, it looks like you have the set screw a little too tight. The servo shouldn't struggle like that. Also, this shouldn't have any impact on the temp, but the damper is upside down. I designed it that way so that if inclement weather came in the fan wouldn't force water into the damper.

Try these settings out:
B: 0
P: 3
I: 0.008
D: 5
min fan: 10%
max fan: 100%
both fan and servo on
 
I used the default settings: b4 p3 i.005 d5 fan and servo with 10/100 min/max

The fire at the beginning was all my fault. I know how to start low slow fires, but I forgot about the et732 probe issues that I read about during my 1st v4.1 attempt. I started the fire then connected the pit probe, nada. Then remembered the et732 room temp issue, so I turned the fan on manual and left it like that, but I forgot about the et732 length issue, and by the time I figured that out, the grill was at 180 having with the fan on the whole time. Won't make that man fan mistake again.

Realizing 225 was a lost cause I upped the set point to 300 and tried to see what the HM would do there.

As for the damper, thanks for the heads up on orientation. I was wondering that myself, though weather is rarely an issue for us in SoCal. When you say the servo was struggling, I assume you mean that rattling/vibration right? I don't know what it is but the servo wants to do those little vibrations/chatters a lot, regardless of how loose or tight the set screw is. It'll do it at standstill. I'm thinking its either the cheapo servo itself or one of the wire connections in the damper's cat5 port?
 
Hmm... so i'm getting a massive overshoot again... fan was blowing above 40% all the way to the setpoint before shutting down. Overshoot reach 273, 20 minutes after crossing 225 before coming down.

How do I teach it to do a better job of walking the temp up and holding at the setpoint?

m9oxvs.jpg


30m4u34.jpg
 
You can't really "teach" it to do that. The problem that you are having is that air is getting into the smoker with the valve closed. Check your seals around the smoker and the damper mount.
 
Tom Kole said:
You can't really "teach" it to do that. The problem that you are having is that air is getting into the smoker with the valve closed. Check your seals around the smoker and the damper mount.
Click to expand...

You know what... I did notice smoke seeping out where the ash pan connects to the fire box. It never does that! I'm guessing the weight of the damper is enough to pull it down and mess with the seal. I'm going to use my chimney starter to push the pan up snug, and see what that does.
 
Tom Kole said:
The problem that you are having is that air is getting into the smoker with the valve closed. Check your seals around the smoker...
Click to expand...

You couldn't have been more right. I can't believe I never noticed before, but the welding job on my akorn's ash pan is pretty shoddy. There are gaps where the flat top meets the lower bowl, especially on either side of the vent control and the left side hanger catch. I've never really had problems with temp control manually, so I didn't think to check for leaks, but it's pretty easy to see how a fan stoked fire desperate for air can suck more air in.

The boards suggest this is pretty common, but I've emailed chargriller about a replacement so we'll see. With Chargriller's reputation for quality craftsmanship. There's probably a good chance that any replacement will have similar issues. Either way the mods I've seen are solid and I'm sure I can fix it.

Damn, I just want to cross the finish line already!
 
I had similiar problems until I sealed it really good. I bought some green egg gasket and sealed the lid and lower damper. I bent the latches so they clamp down harder. I also start the fire with a cotton ball soaked in alcohol. This starts a lower temp fire and cuts down on over shoot. I can run at 225 for over a day on one load of lump charcol using the default settings. I do use my own servo damper with the fan in the wiki.
 
JBond said:
I had similiar problems until I sealed it really good. I bought some green egg gasket and sealed the lid and lower damper. I bent the latches so they clamp down harder. I also start the fire with a cotton ball soaked in alcohol. This starts a lower temp fire and cuts down on over shoot. I can run at 225 for over a day on one load of lump charcol using the default settings. I do use my own servo damper with the fan in the wiki.
Click to expand...

Thanks. I ordered the BGE nomex gaskets for that mod. On top of what you did, I also need to take the ash pan apart, seal the bowl with RTV, and put some nomex behind the vent control. I want to give chargriller a chance to address as well. Check out the gaps I have at the seam on the very edge of the ash pan. It's like that on both sides of the vent control, and a smaller one about the catch for the latch on the left hand side.

2sa0wtu.jpg


I also use the cotton ball method, so I'm good there. For now, if I bring the temp up manually, put fan on at max only & drop the max fan speed to 50%, I can use the HM to hold the temp. I just can't use the fan to bring the temp up yet (because of the airflow issues).

I did an actual cook this weekend and the HM held 225 fine for hours once I got there.
 
yeah mine looks much better around the ash pan. Bending the latches sealed it up really tight so much so i never used the atv sealant I bought. I let the cotton ball burn for 10-12 minutes, close it all up, then I let the heatermeter take over. With those mods you be happy. I only adjust the top vent for the desired temp.
 
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