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January 14th, 2019, 5:49 pm
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This article will use some hands on testing to illustrate the lessons learned in the previous article.

We will use a temperature logging tool that is readily available to anyone, to run some simple tests and show how the gradient heat works in the Yoder Smokers pellet cookers, and how an aluminum pan, introduced into the cooking chamber, affects temperature performance.

We will use a Fireboard temperature logger to gather the data and chart the test results: https://www.atbbq.com/fireboard-fbx11-w ... ition.html

The photos and test results from this test are from a well used Yoder Smokers YS1500 that was built late in 2013. This cooker has cooked thousands of pounds of meat, burned through tons of pellets, and has been the guinea pig for engineering and programming changes. It is currently running B20 firmware and configured like the cookers currently leaving the factory, with the exception of a fixed chimney stack (not removable) and an original burn grate (not reinforced). The pellet fuel that is exclusively used is a 50/50 mix of BBQR's Delight pecan and cherry. In consideration of this, if the reader attempts to exactly duplicate the listed results, there will be differences and variations in the data, but the overall findings should be the same.

The YS1500 HMS plate damper was left fully closed (pushed in) and the YS1500 chimney damper was wide open from the start to the end of this test. Nothing was changed or modified during the test.

We will use 4 Fireboard temperature probes for this test. There will be 2 Fireboard meat temperature probes, one on the lower grate and one on the upper grate, placed in the approximate center of the cooker, and 2 fireboard ambient temperature probes, one on the lower grate and one on the upper grate, mounted in Fireboard probe holders 1" above the meat probes lying on the grate surface. The goal is to simultaneously record 4 temperature locations, over 5 hours, to illustrate the gradient temperature in the cooking chamber, from bottom to top, and the effect an aluminum pan has on the temperatures inside the cooking chamber.

This is how the 4 Fireboard probes were arranged in the cooker. The placement is approximately in the center of the cooker, and placement was predicated on the attachment of the probe holder to the grate.

Upper grate


Lower grate

Showing upper and lower probes from above the upper grate

This is the upper left hand door gauge at 1 hour

This is the lower right hand door gauge at 1 hour

This next pictures are of the pan that was put into the cooker at the 2.5 hour point, and probe placement



I made an all inclusive chart to illustrate the test results and to better explain the clear conclusions

All of the data came from the captured data from the Fireboard session, with the exception of the controller display temperature, which was captured directly to a laptop using our internal proprietary testing tools. The Fireboard session data was downloaded at the highest resolution of data points, and then put into a spreadsheet to chart and calculate the results shown in the chart.

In any testing that we do at the factory, we always drop the first 30 minutes of a cooking session to allow for the initial ignition and warm up of the cooker. Including this data provides erroneous results for the targeted data set(s). At the 2.5 hour mark into the test, I opened the lid, put in the aluminum pan, and positioned the lower grate probes exactly in the same location as the first part of the test. Please notice that we did not drop the next 30 minutes of data starting at the 2.5 hour mark in the test, like we did with the YS640 test after the pan was put into the cooker. The YS1500 has a much heavier metal mass, allowing the temperature to almost immediately recover and return to normalization, unlike the YS640, which took approximately 30 minutes to recover normalization.

So what the chart illustrates, is the total of a 5 hour test run at 250 degrees, with the first 30 minutes dropped from analysis for the cooker to start and warm up. This gives us a 2 hour data set before the pan was put into the cooker, and a 2.5 hour data set after the pan was put into the cooker, to analyze and compare.

The first 2 hour data set is showing the temperatures of the 4 probes with the cooker running at a set temperature on the controller of 250 degrees. The focus is placed on the resultant averages over this 2 hour period of time, which are listed in the box below the charted data. This clearly shows the normal gradient temperatures in the cooker, from the bottom to the top. This is called "cooking from the bottom up". Of interest, and one of the most asked questions, and the source of confusion, is that setting the temperature on the controller directly correlates to the physical lower grate surface; there is a drop in temperature at one inch above the grate surface, and an even greater temperature drop at the upper grate surface and one inch above the upper grate surface. So, the temperature that you set on the controller, is going to be an approximation of the physical grate surface of the lower cooking grates. Any temperature reading(s) not taken from the physical grate surface of the lower grate are considered suspended air temperature, as the temperature probe taking the temperature reading(s) must be suspended in the air space above the physical surface of the lower grate. In this test, probes #2, #3, and #4 are all gathering suspended air temperature readings. Another clear takeaway, and source of confusion, is that there is a temperature differential in just the first inch of air gap above the physical lower grate surface. Run this test periodically on your cooker to know how your cooker is performing and to keep up with the its ever changing dynamic.

In the second 2.5 hour data set, again, focus on the data averages in the box below the charted data. Nothing changed from the first 2 hours of the test, except for placing a full size aluminum pan in the cooker and putting the lower grate temperature probes inside the pan.

Putting the pan in the cooker shows not only the change in the effective cooking temperature inside the pan, but also the effective cooking temperatures on the upper grate surface and above. Owners will cook meat in a pan, or put a pan under what is cooking on the upper grate to catch drippings, or specifically to keep the lower portion of the cooker cleaner. It is a personal choice to use pan(s) in the cooker, but the changes that are made to the cooking environment must be understood, and compensated for.

As you can see, cooking in a pan will drastically change the effective cooking temperatures. In the case of this specific test cooker, it is a well seasoned and properly maintained YS1500. Through the life of this cooker, the temperatures inside the cooker gradually started to run slightly hotter than the controller display, and have settled into what you see today. Any cooker will get better with usage, and the more it is used the better it will get.

Also, putting liquid in the pan complicates things, as the physics of the maximum temperature obtainable from the boiling liquid must be considered. i.e., water changes to steam at 212 degrees at sea level, and the resultant steam maximum temperature, directly above the liquid, which in this case, unlike in a pressure cooker where water boils at a higher temperature and the resultant steam is also hotter (superheated) because of the increase in atmospheric pressure, will be the temperature of the boiling water which quickly cools the further the steam gets from the boiling liquid.

Here are some related articles for your review:

Pan(s) in the cooker: viewtopic.php?f=36&t=1392
Cooking with grate temperature or suspended air temperature: viewtopic.php?f=49&t=1368


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