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Z Grills – Controller Operation

Z Grills pellet smokers burn wood pellets that are intermittently dropped into the fire-pot. Let’s have a look at how the controller manages the operation of the ignition rod, auger motor and fan to achieve automatic temperature control.

Z Grills pellet smoker automatic controller

Starting the Z Grill

Whenever the controller is switched from Shut Down to Smoke a set sequence of operation occurs to establish a fire in the fire-pot.

  1. The ignition rod is powered for 5 minutes, getting red hot to ignite the pellets.
  2. The auger rotates intermittently to deliver pellets into the fire-pot.
  3. The fan runs as full speed to deliver oxygen to the fire-pot

After about 4-5 minutes a fire is established in the fire-pot and the temperature in the grill begins to rise. Once the controller detects the temperature is above 60ºC it goes into automatic operation to reach the set temperature.

Automatic Temperature Control

  1. Pellets are delivered to the fire-pot by the auger every 45-90 seconds, depending on the temperature setting and how far the current temperature value is from that target setting.
  2. When the temperature is a long way below the target temperature the auger motor will run almost continually to deliver lots of wood pellets to build up the fire. As the temperature approaches the target, the controller will reduce how long the auger runs each cycle.
  3. Gradually the controller “learns” the right combination of on/off run time for the auger to maintain the target temperature.
  4. Each time newly delivered pellets ignite, the temperature will rise and can slightly exceed the target temperature, result in small temperature “swings” around the target.
  5. The temperature can swing as much as 20ºC either side of the setting, especially during the first hour of operation, after any temperature setting changes, or if the lid is opened for several minutes. This is normal.
  6. Because the heat is indirect this temperature cycling will not adversely effect the cooking of food.
  7. The grill temperature is measured at the left side of the grill toward the top of the grill drum by the long metal temperature sensor. Particularly as the grill first heats up, the temperatures on the main grill rack may be 10-15ºC lower than the LCD display but will stabilise to be similar over time.
Z Grills Control Thermometer
Grill temperature sensor

The graph below shows the temperature of the grill rack measured over a 5 hour cook. The swings shown are perfectly normal.

Actual temperature and swings are impacted by a few factors as listed below.

  • The temperature setting (more swings at lower temps)
  • The weather (humidity, temperature and wind)
  • The type of pellets being used (different heat output)

Initial Startup Temperature Spike

In the graph above, note the temperature spike at startup. This is due to the large number of wood pellets initially dropped into the fire-pot to establish a good fire. As they burn they release a lot of heat.

If planning to cook at a low temperatures (<121oC / 250oF), simply leave the lid open for a few extra minutes after the first cloud of smoke clears to release heat and avoid an initial temperature spike.

I want to understand even more!

Check out the video below which shows all the key components and how the they work together.

Updated on October 4, 2020

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