The Mystery of Controlling Heat

March 22, 2011 by  

Click Author Nickname for Bio > homebbq

By Kevin Bevington

This is probably the single biggest obstacle to many beginner bbq’rs, in fact the unfortunate thing is many start out with the cheapest smoker they can buy, and don’t understand that they have just purchased a cheap piece of equipment, loaded with design flaws. However, they are fairly easy to overcome if you understand the basics to controlling heat.

First, heat is produced by fire, whether it is wood, charcoal, or gas (we will talk about electric in a minute). A fire needs air to stay lit, right? Most of us somewhere in life have attempted the experiment of putting a candle in a jar, and watched it go out, as soon as it ran out of air.  The same applies to a smoker. We can now control the size of the fire, with the amount of air. Increase the amount of air, and you can increase the intensity of the fire (assuming you have enough fuel). Decrease the amount of air, and you reduce the intensity of the fire.

Second, you need to have somewhere for the smoke, and heated air to go. If you put an air tube in the jar with the candle, pushing air in, the candle would still eventually go out, suffocating from it’s own smoke. The same applies to a smoker, you need an escape (or vent) for the smoke and heated air.

Third, we have all learned somewhere that heat rises, so if we put an exhaust tube at the top of the jar, we have now created a vent, or escape for the smoke, and heated air. If we fit this tube with a valve, we can now control the amount of air leaving the jar. Now, along with controlling the amount of air going into the jar, we now have complete control of the intensity of the candle burning inside the jar.

Your smoker comes with the same elements. First you have a grate or pan that holds charcoal or wood, and vents that control incoming air, and a vent at the top of the smoker to control the air or smoke going out of the smoker. If we have a fire burning, and both vents wide open, then we have an intense fire, and a hot, clean (little smoke) cooking environment . If we close down the top exhaust vent some, we have now decreased the flow of air leaving the smoker, and are now trapping some of smoke for a longer period of time in the cooking chamber , and we now have a not so clean (smoky) cooking environment. This also reduces the draw of air and does decrease the intensity of the fire, by reducing the amount of air being pulled through the cooker..

If we now close the incoming vent, we have decreased the amount of air going in, and we have then decreased the intensity of the fire, and will decrease the temperature in the cooking chamber, because we have now not only decreased the volume of the fire, but the amount of heated air traveling through the cooker.

Until  you get a hang of things, the best way to do this is to maintain your exhaust vent control at either a full open, or slightly less than full open, and control your temperature purely by controlling the incoming airflow. When you get the hang of things, you can then fine tune your cooking environment using your exhaust vent control.

It could take a few tries before you get the hang of this, but once you do get the hang of it, you will then be able to control your cooker, and produce the cooking temperature your looking for.

In a charcoal or wood fire, we have to be concerned with more than just air coming in and leaving the cooker. We also need to be concerned with waste (ash) blocking the air from getting to the fire. In a cooker, in order for heated air to flow, and for the fire to stay lit, air needs to get underneath the fire.

In many low budget charcoal cookers, they don’t necessarily take this into consideration and don’t  give any room for ash accumulation. When you burn charcoal or wood, this will produce ash, and some charcoal brands will produce large amounts of ash. If your using a charcoal pan, and just place your charcoal in the pan, and you manage to get it lit, your fire will be choked and put out by ash, before it ever runs out of fuel, and regardless of the amount of air given to it.

You need to use a charcoal grate, and have a minimum of 2 inches (more if possible), to allow for ash accumulation, and still give enough space for air to get underneath your fire.

In charcoal, wood, gas, and pellet cookers you need to account for the amount of fuel you will need to complete your cook. There is no exact method to figure this out, because it will vary based on cooking temperature, quality of fuel used, external temperatures, physical size of the cooking environment, etc. But here is a guide:

Charcoal – roughly 2-3lbs per hour

Gas – .5 to 1lb per hour.

Wood Pellets – 1lb per hour

Wood sticks (logs)- 2 to 3 per hour

Always over estimate your need, and you should be ok, you never know what may happen at any time to cause you to use more fuel than anticipated.

When using an electric cooker, you really don’t have the concern of having enough fuel, or the concern of having the airflow to keep the fire alive. Just make sure the power does not go out.

Forced Air Draft

What is forced air draft?  This is a fancy way to describe blowing air into a fire, and not relying on natural draft. This is most commonly and effectively done using a fan controlled by a programmable thermostat.

These devices are available for purchase to fit most cookers, and come built into pellet cookers, and some insulated charcoal cookers. These devices really help to control the temperature in your cooker, keeping it consistent, which will conserve your fuel giving you longer burns.

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One Response to “The Mystery of Controlling Heat”

  1. CarbonThief on September 24th, 2011 1:42 pm

    Excellent article, well articulated, as always! Thanks for your insights on what I would agree to be the most difficult learning curve for BBQ, controlling and maintaining the desired heat range!


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