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[Hank D Thoreau]

This past Sunday we had a plan to cook ribs for a quest. As the number of folks expected increased, I decided that I need to cook a bit more.

I had three packages of short ribs, two packages of beef ribs and two chuck roasts.

We had decided to cook the ribs two ways and see which turned out the best. Half were cooked in a crock pot over night on low. The other half were cooked in the smoker along with the two beef chucks.

My concern was that adding the ribs would impact the time it took to cook the beef chucks, which normally take me 8 to 9 hours using the "Best Beef Chuck So Far" method.

I have used this method to cook dozens of beef chucks over the past few years and it is very predictable.

https://pelletfan.com/index.php?topic=4893.0

I had experienced a similar problem while cooking two pork butts. Conventional wisdom was that would take the same time as one, but that did not turn out to be the case.

https://pelletfan.com/index.php?topic=3909.msg47080#msg47080

It turns out that my beef chucks really lagged. I hit a stall around 150 and did not see a rapid rise after rapping. Per the method, I would take the chucks up to and IT of 210 and hold them there for an hour.

I never managed to get them that high. I finally ended up pulling them after about 11 hours. Since cooking depends on both time and temperature, it turns out that the chucks were fine.

The extra 3 hours were enough to make up for the lower internal IT.

After about 3 hours the ribs were placed in two aluminum trays with foil on top. One tray was placed on a rack. At this point the smoker was pretty full.

Part way through the cook, I pulled one tray of ribs out of the smoker and stuck them in my oven since they were already wrapped. I pulled the second tray later to take the stress of the smoker.

I also completed the ribs in 11 hours before saucing them and placing them under the broiler for about 10 minutes.

The sauce was to tone down the very peppery rub that I used. Next time I will put less rub on. The ribs, however, turned out great.

Below is the temperature profile for the cook and some pictures taken during the process.

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[pmillen]

If one beef roast takes 8 hours to cook, how long will two require?

As I mull that over I always arrive at the same conclusion; 8 hours, assuming that the pit can maintain temperature when two roasts are absorbing the heat.  As you wrote, "Conventional wisdom..."

Yet, empirical data consistently shows that it will take longer.  I wish that I knew the science of it.

[Hank D Thoreau]

If one beef roast takes 8 hours to cook, how long will two require?

As I mull that over I always arrive at the same conclusion; 8 hours, assuming that the pit can maintain temperature when two roasts are absorbing the heat.  As you wrote, "Conventional wisdom..."

Yet, empirical data consistently shows that it will take longer.  I wish that I knew the science of it.

My standard is based on cooking two beef chucks. I learned that one beef chuck does not go very far at my house.

I believe that the science lies in how a convection oven controls temperature.

It is important to recognize that it is energy that cooks food and not temperature. The job of the smoker controls is to maintain a set temperature at the sensor by burning pellets. It is the burning of the pellets that create energy.

The energy is used to cook the food and to excite the air molecules in the smoker.

The key is that the smoker does not burn more pellets because the food demands more energy, rather it does it because it needs to raise the temperature of the surrounding air.

If I put two large trays full of ribs in the smoker (or two large pork butts), the amount of air necessary to heat is less and requires less energy to maintain. Thus, less pellets are burned.

Also, as the food rises in temperature, the food itself starts to act as an insulator, absorbing less energy from the air which leads to less pellets needing to be burned to maintain temperature.

The conclusion is that while putting more stuff in the smoker results in more energy being absorbed, but less energy than is expected will be necessary to maintain temperature, which is how energy creation is controlled.

I speculate that this is more of an issue with low and slow cooking since there is a smaller temperature difference between the food and the surrounding air. As such, the food will act as a better insulator.

[BigDave83]

I have not noticed any noticeable difference in time when doing  1 rack or 5 racks of ribs. Butts I do in the little electric cookshack, it don't get no easier, put in 1-4 of them toss some wood in the box close the door turn it on and come back in about 13 hours and take them out.

 A lot of people test temp differences in an empty cooker, adding one or more things and difference in size should affect temps across the grate in my mind. This would be to me because the pellet cookers are a convection oven for the most part so anything that disrupts the air flow will affect the temps.

I guess I could understand a time difference as the more meat will take longer to come to temp and keep absorbing energy as it does, but along those lines the energy would be temp decrease so the controller should account for that and keep the temps where they need to be.


 No matter how it works, it looks like some good eats for those that were in attendance. I would have been happy showing up ad seeing that.

[Bar-B-Lew]

On the majority of my smokers I don't recall having it taking longer to make more food on them as long as I had enough space in between the cuts.

[Hank D Thoreau]

This is where you really need to recognize the difference between temperature and energy. Temperature does not cook. Energy cooks the food. Temperature is used to control the combustion of pellets that release energy.

Consider two insolated boxes of vastly different sized. The first is the size of a shoe box and the second is the size a room. It takes far less energy to raise the temperature of the shoe box to a set temperature than it does for the room.

More pellets will be consumed heating the room (like a pellet heater), and as such, the room will contain far more energy.

Now imagine that I am cooking a pork butt in both the shoe box and the room maintained at the same temperature. The butt in the shoe box will start pulling from the limited amount of available energy. Pellets would have to be burned as energy is absorbed by the butt. Energy absorption is a slow process, much slower than energy is released from the burning of pellets. As such, it does not take a lot of energy to maintain the temperature of the shoe box, especially as the temperatures of the box and the butt start to approach each other in a low and slow fashion. Cramming another pork butt into this very large shoe box (clown shoes) would result in even less air space to heat.

The room is far different. In this case it takes a lot of time and energy to heat the room to the cooking temperature. The butt then uses the energy already in the room to cook, with little need to burn additional pellets to maintain temperature (we are assuming perfect insolation for these examples). I could probably put many pork butts in the room with little impact since the amount of energy in the room far exceeds what it takes to cook.

In a smoker, pellets are burned based on the temperature in the area of the sensor. The amount of pellets that have to be burned is related to the volume of air that must be heated, and energy that is being absorbed by the meat, the later depending on the difference in temperature between the meat and the surrounding air.

I suspect that the problem is the design of the smoker I am using. You can think of it as an efficiency issue. I have cooked dozens of beef chucks and understand the variation in cooking profiles I get. This time was a clear outlier from what I see, just as it was with the two pork butts that I cooked at the same time (see the thread in my first post).

[Bar-B-Lew]

"I suspect that the problem is the design of the smoker I am using."

Ding ding ding, you have a winner!

[02ebz06]

I would think that more cold mass in the smoker would have some effect.
Not sure what or how much though.

[Hank D Thoreau]

I would think that more cold mass in the smoker would have some effect.
Not sure what or how much though.

It probably does and this is why temperatures go up quickly in the beginning when doing low and slow. As the cold mass heats, the temperature difference gets small and the food starts to act as an insulator.

It would be interesting to do some real functional testing on pellet smokers to look at things like temperature variations across zones and the impact of increased loads on cooking times.

I get a lot of temperature variation across my original GMG Daniel Boone. It is not very easy to adjust the temperature balance since you have to take out the grill grates and heat shield to adjust the position of the heat shield.

You have to wait for the grill to cool to make each adjustment. I thought the addition on the prime version of the slider for the heat shield was a good idea. I was thinking of a lead screw but that was probably too costly for a low-cost smoker.

I just place ambient probes in the grill and have learned to adjust. Also, since I am using a four channel Signals temperature probe I can monitor a chart of the cook which helps me drive the process, especially with the "Best Beef Chuck so Far" method where I hold at IT 210 for at least an hour.

[BigDave83]

I would think that more cold mass in the smoker would have some effect.
Not sure what or how much though.

It probably does and this is why temperatures go up quickly in the beginning when doing low and slow. As the cold mass heats, the temperature difference gets small and the food starts to act as an insulator.

It would be interesting to do some real functional testing on pellet smokers to look at things like temperature variations across zones and the impact of increased loads on cooking times.

I get a lot of temperature variation across my original GMG Daniel Boone. It is not very easy to adjust the temperature balance since you have to take out the grill grates and heat shield to adjust the position of the heat shield.

You have to wait for the grill to cool to make each adjustment. I thought the addition on the prime version of the slider for the heat shield was a good idea. I was thinking of a lead screw but that was probably too costly for a low-cost smoker.

I just place ambient probes in the grill and have learned to adjust. Also, since I am using a four channel Signals temperature probe I can monitor a chart of the cook which helps me drive the process, especially with the "Best Beef Chuck so Far" method where I hold at IT 210 for at least an hour.

 If the deflector plate has a bent corner, put a hole in it a long piece of 1/4" all thread a couple of nuts on either side or the deflector plate to hold the rod then drill hole in the body run the rod through and use a wooded drawer pull in the end of it.

I had thought about doing that with mine then I thought I have no idea how far temps are off so I'll just cook on it the way it is. Mine seems to run hotter than set temp.

[Hank D Thoreau]

I would think that more cold mass in the smoker would have some effect.
Not sure what or how much though.

It probably does and this is why temperatures go up quickly in the beginning when doing low and slow. As the cold mass heats, the temperature difference gets small and the food starts to act as an insulator.

It would be interesting to do some real functional testing on pellet smokers to look at things like temperature variations across zones and the impact of increased loads on cooking times.

I get a lot of temperature variation across my original GMG Daniel Boone. It is not very easy to adjust the temperature balance since you have to take out the grill grates and heat shield to adjust the position of the heat shield.

You have to wait for the grill to cool to make each adjustment. I thought the addition on the prime version of the slider for the heat shield was a good idea. I was thinking of a lead screw but that was probably too costly for a low-cost smoker.

I just place ambient probes in the grill and have learned to adjust. Also, since I am using a four channel Signals temperature probe I can monitor a chart of the cook which helps me drive the process, especially with the "Best Beef Chuck so Far" method where I hold at IT 210 for at least an hour.

 If the deflector plate has a bent corner, put a hole in it a long piece of 1/4" all thread a couple of nuts on either side or the deflector plate to hold the rod then drill hole in the body run the rod through and use a wooded drawer pull in the end of it.

I had thought about doing that with mine then I thought I have no idea how far temps are off so I'll just cook on it the way it is. Mine seems to run hotter than set temp.

I thought of retrofitting mine a few years ago but did not since that would void my warranty.

I know how far my temps are off and where. I ran a test with four probes. I have constant temperature front to back, but a significant difference left to right with the smoke stack side being hotter.

I run two ambient probes when I cook, on the left and right sides.