How a pellet grill controls its heat: auger, fan and fire pot

What is the grill doing when it feeds pellets in bursts?

It's following a schedule. Each part has one job, and the controller decides when each one works.

The pellets sit in a box called the hopper. A motor turns a screw-shaped rod, the auger, which pushes pellets into a small metal cup called the fire pot. That's where they burn. One reference describes it this way: "A motor-driven auger then feeds a small amount of pellets from the hopper to the fire pot"¹.

What does the fan do?

A fan pushes air through the fire. The same source says pellet grills "use automated fuel and air delivery"¹. Fuel and air go in together, and the mix sets how hot the fire runs.

Your own manual says where the fan sits and what it does on your model.

Why does it feed in bursts instead of steadily?

The auger doesn't run all the time. It works in a cycle of run and rest, called a duty cycle. The rest period changes with the setting: "Lower temperatures have longer auger-off periods, while high temperatures have shorter periods"¹.

So at a low setting you'll hear long quiet gaps between feeds. At a high setting the pauses are short.

A duty cycle can be given as a percentage of time the auger runs. An auger that runs half the time has a 50% duty cycle, for example¹.

Who decides how much to feed?

A sensor and a controller. The controller reads the grill's temperature and changes the feed. When the weather works against the grill, it reacts. One retailer says the control unit "combats this by adding more pellets to raise the internal temperature to your settings"².

Some controllers adjust as they go. One kind, called a PID controller, learns how much fuel it takes to raise the temperature. "These adjustments continue for hours, even after the programmed temperature has been met"¹.

Which kind of controller your grill has is in your manual.

Why does this cause up-and-down temperatures?

Because the heat isn't instant. Fuel goes in, burns, and warms the air, and only then does the sensor notice. By that time the controller may already be planning the next feed. A little overshoot and undershoot is built in.

That's why one maker likens its grill to a home oven, where the temperature averages out over a cook³. The display shows the live number, not the average.

What should you not do?

Follow the start-up, shut-down and troubleshooting steps in your own manual, since each model's order is different.

For what changes the cycle from outside, see outdoor weather and pellet quality and moisture.