AutoDraft Temperature Control
A barbecue pit is just a wood-fired oven, so controlling temperature is important. Many factors (e.g., wind, rain, meat load) influence temperature, but the biggest driver is the amount of heat transferred from the fire to the cooking chamber.
Ordinary pits share one key attribute: 100% of the power produced by the fire goes into the cooking chamber. As long as controlling the fire power is easy, as in the Charcoal Cooker and Electric/Gasser pits, there’s no problem controlling pit temperature. But a wood-fired pit (a.k.a. a Stick Burner) is a totally different animal:
- The Fire Triangle: a fire’s power will be limited by fuel if we have good (hot) geometry and surplus of air to avoid making creosote.
- How Wood Burns: wood isn’t fuel. It’s a fuel source, which produces two fuels (smoke and charcoal) as it decomposes under heating.
From a control standpoint, that is a huge difference. It means that the power of a clean-burning wood fire is determined by the rate of decomposition of wood into charcoal and smoke.
Right about now, you should be experiencing a growing sense of awe for the True Pit Boss. Some people can build a clean-burning wood fire. Others can build a wood fire that keeps the pit steady at X degrees. Few can do both at the same time, because that demands a thinking process that is a full step ahead of the current pit temperature.
The True Pit Boss gages when to add a log based on its size, shape and moisture content, the temperature of the fire itself, the state of decomposition of the logs already in the fire, coming changes in meat load and weather, etc., etc. And the only calculator he has is the pattern recognition capability gained from an enormous amount of experience.
KBQ® technology breaks down this experience barrier by disconnecting the fire’s power output from the pit’s power demand. AutoDraft replaces the traditional smokestack with a fan that draws air from the Cookbox and discharges it overboard. Because a KBQ® Firebox intrinsically controls smoke quality over the full demand range – from shutoff to 100% power – temperature control is easy. When the fan runs, it draws a slight vacuum in the Cookbox, which in turn draws hot smoke from the Firebox. When the fan cycles off, the fire reverts to normal, with no heat entering the Cookbox. The fan is controlled by a simple thermostat, which regulates temperature in a tight band.
Being a forced-air, pull-through system, AutoDraft temperature control brings a number of additional benefits:
- The system is inherently fail-safe. Loss of electrical power immediately stops heat transfer because components are arranged to prevent a natural draft from occurring.
- Physical separation of the Firebox and Cookbox ensures grease and fire never meet.
- The Firebox has no attached energy sources (e.g., electric components, natural gas lines).
- A recirculating convection fan can be added to the cooking chamber without the concern of disturbing a delicate natural-draft system. This improves heat transfer to shorten cooking times by 25% or more and significantly improves temperature uniformity.
- With a hot, powerful fire always on standby in the Firebox, temperatures recover within a few minutes after loading and/or unloading the Cookbox.
- When the cooking chamber is opened, the AutoDraft suction path is broken, automatically stopping the flow of smoke from the Firebox into the Cookbox and evacuating the Cookbox by drawing fresh air through the open door.