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**Pellet cookers** - YS480, YS640
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May 5th, 2019, 2:43 pm
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The Yoder Smokers pellet cookers were designed to mimic the functionality of the Yoder Smokers offset wood pits, with the exception that the fire is managed by the digital controller, rather than the cook periodically putting wood on the fire.

The Yoder Smokers pellet cookers utilize a large offset firebox and grate, which allows for a large and efficient fire, and the flow of smoke and heat through the full length of the cooker. Because the fire is larger, and is burning wood (pellets), the changes to the fire (heat) are not instantaneous, nor will the temperature in the cooker be a flat line constant, which is caused by the fuel (pellets) added to the fire being of differing sizes and amounts for every iterative turn of the auger. So just like cooking on any offset wood pit, you manage the fire based on the average temperature over a time period.

Calibration of the ACS controller is a new function that allows you to "dial in" your cookers performance, based on your requirements. This calibration is NOT something that you do constantly, but rather something that you may do to periodically to baseline your cooker's performance. Calibration is NOT required for you cooker to function, but allows those that desire a tighter control over the performance of their cooker, to make the necessary changes to match their desired level of performance. NEVER change the calibration of the controller with food in the cooker, as calibration is a function that requires a specific set of parameters to be followed when the cooker is empty.

The new ACS controller comes with the calibration set to 0 (zero), which means that the controller will manage, and adapt, in maintaining your desired set temperature. If you desire to achieve a tighter control on the temperature management in the cooker, or want to change from the controller using physical lower grate temperature to some level of suspended air temperature, the new ACS controller allows you to calibrate this directly into the controller using the menu on the controller.

I updated my early 2012 YS640 competition cart with the ACS controller. After I installed the controller, I ran the cooker through the 2 hour factory temperature test (using the 2 built in probes and Fireboard session for data and graphs), and was well pleased with the performance of the cooker without doing any calibration at all. The cooker heats up much faster, and settles in to your set temperature much quicker that the original controller. The pellet consumption seems to be less than before (I only use BBQR's Delight pellets, so this may be different for you if you use a different brand - results may also be different using a different brand of pellets because of lower BTU consistency). There seems to be less ash left in the burn grate after running, and the residual ash seems to be finer than previously seen with the old controller, with more residual ash dropping into the firebox through the burn grate.

I decided to calibrate the controller to see how the process works and what the process does, and how it would affect the performance of the cooker. The process to calibrate is outlined below.

To calibrate the cooker, the cooking chamber needs to be cleaned to remove all residual cooking debris, grease and ash. I keep the inside of my cooking chamber pretty clean, so all I needed to do was to completely vacuum all the ash from the inside of the cooker, the firebox and the burn grate, paying attention to also vacuum the ash from the igniter tube. Once I had the cooker cleaned, I made sure that the burn grate fitment in the firebox was up to factory specs, installed the 1 piece diffuser and the lower cooking grates, and pulled the sliding damper all the way open (handle pulled out fully to the right). I then attached the 2 temperature probes to the new ACS controller, put them through the factory probe port (I had previously installed the new factory probe port in the factory location on the left side of the cooking chamber - https://www.atbbq.com/yoder-smokers-pro ... style.html) and laid the directly on the lower cooking grate with one of the probe tips at 11" and the other at 22" from the hopper wall.

probe placement.jpg

After getting the probes placed, I closed the probe port door and closed the cooking chamber lid. I plugged in the cooker, pushed the power button, and pushed the START button, then set the controller to 250 degrees by turning the dial counter clockwise. To verify, I went to the calibration screen and made sure that the calibration was set to 0 (zero).

start button pushed.jpg

Here is the Fireboard session chart for the entire calibration test

fireboard session.jpg

At about the one hour mark, the grate probes had been reading lower than the cooker thermocouple, so I set the calibration to a -5 (minus five) to tell the controller that the physical grate temperatures had been reading an average of 5 degrees lower that the display. I set the -5 by pushing in on the dial to select the change, and then turning the dial counter clockwise.

setting first calibration.jpg

This is what the -5 calibration looks like after verifying the setting by pushing in on the dial.

calibration set to -5.jpg

I then let the cooker run for approximately 30 minutes to settle in with the new calibration change. I noticed from the session chart that it seems that the -5 change was making things a little worse that what I had expected, so from looking at the average differences between the grate probes and the cooker's thermocouple, I changed the calibration to +5 (plus 5), which accounts for a 10 degree upward change in temperature, i.e., -5 to +5, which is effectively is setting the calibration to +5 from the default 0 (zero) calibration. So the end result is that I told the controller that the display temperature of the cooker's thermocouple was an average of 5 degrees cooker than the actual temperatures of the grate probes.

calibration to +5.jpg

I let the cooker run for a total of approximately 3 hours, from pushing the START button until I pushed the power button to shut the cooker down. By the end of the session, the temperature of the display and the two grate probes were within 2 degrees of each other, and the overall temperature averages were within 1 degree of each other. I would say that the cooker and ACS controller are calibrated, and performing as they were designed.

3 hours into calibration before shutdown edited.jpg

After going through this 3 hour process, personally, I am not sure that I would suggest that the time spent doing the calibration wouldn't have been better spent cooking some lunch, as the ACS controller actually does a stellar job of managing temperatures all on it's own.

As a side note, here is a photo of the residual ash from the 3 hour calibration test, using a 50/50 mix of BBQR's Delight pecan and cherry. You can use this to compare with your residual ash if you decide to do this calibration test. Notice the lack of any fluffy whitish fly ash. Unlike most other pellets, BBQR's Delight has no bark in the pellets, and are super consistent from bag to bag and pallet to pallet.

residual ash.jpg

May 5th, 2019, 5:26 pm
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Here is a follow up and some vital information.

I decided to run another the 2 hour factory temperature test, just to verify the calibration test I did was correct. I cleaned all of the residual ash from the cooker, firebox and burn grate (as I always do), and placed the temp probes back exactly as I had done for the calibration test, and started the cooker.

Here is the vital information: I neglected to change the default temperature of 350 on the controller, to my desired temperature of 250 for the 2 hour factory temperature test. After pushing the START button, I walked in the house and was getting a drink of water, when I remembered that I had neglected to change the set temp to 250 on the controller. It was between 2 and 3 minutes before I got the temperature changed from 350 to 250. WOW! The new ACS controller is very quick to heat up to the set temp, and quick to recover when the temperature is changed.

If you compare the graph from the post above, where I set the temperature on the controller to 250 as soon as I hit the START button, and the graph below, where I didn't get the temperature changed for 2 to 3 minutes, you can clearly see the difference. So, if you allow your cooker to always start up at the default 350, you have nothing to worry about. If you want to set your temperature to something other than the default of 350, make sure that you do it as quickly as possible after hitting the START button.

As you can see, the calibration that I did, pulled the controller displayed temperature, and the 2 probes on the grate, right in line with each other, for a very consistent temperature across the grate.

verify calibration.jpg

May 9th, 2019, 10:16 pm
* Abilene ** Abilene *
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Thank you for posting your experiment, it's nice to know we can run a calibration if needed. I can't wait for my YS64s to ship!

July 16th, 2019, 7:44 pm
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Hello Herb. I'm fairly new to the Yoder family. I have been smoking meats for many years and finally decided to get a Yoder and love it. I followed your directions above doing a calibration test because I didn't think the smoker was running as hot as it should. After about an hour, i noticed the pit was running 11 degrees cooler than my one probe. I'll attach pictures. After i calibrated, +6, probe one is only a degree or two off. Probe 1 is 22" inches from the hopper wall. Probe 2 is 11" from the wall. What i can't figure out is why the two probes are 20 degrees different? Any ideas?
I tried to post my pics but apparently i don't know what I'm doing. I have a Yoder YS640S manufactured 6/19
Thanks for any help you can provide

July 16th, 2019, 7:47 pm
* Abilene ** Abilene *
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I forgot to mention, the version is 1.0.5 and the firebird version is 0.2.38

July 17th, 2019, 2:20 am
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Yoder Kurt wrote:I forgot to mention, the version is 1.0.5 and the firebird version is 0.2.38

Please send us your pictures and description of your concern to customerservice@yodersmokers.com so we may properly help.

August 16th, 2019, 3:28 pm
* Abilene ** Abilene *
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Was Yoder Kurt's question ever answered? Calibrated a new YS640S, and all was fine except the probes read 20 degrees different. They were configured exactly as they are in Yoder _Herb's photo above, at 11 & 22. Except I have the 2 piece diffuser. Still love the machine, but I need to be able to rely upon those probes for long cooks.

August 20th, 2019, 8:24 pm
* Abilene ** Abilene *
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norcon6 wrote:Was Yoder Kurt's question ever answered? Calibrated a new YS640S, and all was fine except the probes read 20 degrees different. They were configured exactly as they are in Yoder _Herb's photo above, at 11 & 22. Except I have the 2 piece diffuser. Still love the machine, but I need to be able to rely upon those probes for long cooks.

I've noticed during my experimenting today, that there tends to be a 20º (give or take) split between the pit, probe 1, and probe 2.

For example, today I had the pit set at 250º. The pit was rock steady at 250º. Probe 1 (at 22") read between 5-10º above the pit temp. Probe 2 (at 11") read about 3-5º, but at times 10º below pit temp.

It varied a little, but there was pretty consistently a 10-15º split between the probes, but no matter what that split was, the pit temp was almost always right in between that split.

So I guess you can’t expect the cooker to be the same temp throughout, can you? Seems like we are all having the same issues between probes so maybe it’s normal.

I was surprised the side 22" from the fire was hotter. I was sure the probe closer to the firebox would be hotter.

I found the top grate to be consistently about 10º below pit temp, as advertised.

I also did some experiments where I placed both probes pretty much in the middle of the grill with it set to 250º. Again, the grill was right on the money at 250º, and both probes where pretty close to 250º as well. And they both matched each other as well. Which answers your question. The probes are correct, matching, and accurate.

I know at least have a very good idea of how the heat is distributed thought out the grill for low and slow at least.

As stated in another post, the position of the VDD had very little effect on the temps at all. I think when I moved the VDD closer to the recommended 5-6" in from the exhaust side, the split between the probes seemed to close a little. But who knows, that may have just been an anomaly. Yoder Herb posted a PDF yesterday explaining that the VDD really doesn't do much on the newer grills. It's more of a left over from the early days.

I calibrated my grill based on the past couple days of experimentation, but I actually ended up putting it back to zero cause it was so close to begin with I figured that any give day it's gonna be a little this way or that so why mess with it.

I have noticed that when I set the grill to higher temps (above 400º) the over shoots tend to be MUCH greater (like over 100º above set temp greater), and of course it takes much longer to settle back in if at all. I really haven't used it long enough at higher temps to see how long it would really take to settle in. I can guarantee you it's MUCH more than 30 minutes though. This seems to be pretty common though after reading several others experiencing the same thing. I'm sure that's explained somewhere, just haven't found it yet.

Hope that helps a little.

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