Roasting 101 – Machine Controls

Roasting 101 – Machine Controls


Welcome back to Roasting 101 from Mill City Roasters, here in Minneapolis. In this segment, I’d like to talk about machine controls. Yours may not be identical if you’re roasting with something other than the North.. but i’ll go through the controls, and you’re going to find yours are going to be very similar. Familiarize yourself with your machine controls before you begin. The first one: let’s talk about gauges. I cannot stress enough that machines are not calibrated one to another. So don’t compare your roasts with somebody else based on gauge settings. In our case, our gauge reports back for both propane and natural gas. Propane in kPa… Or, for natural gas, millimeters of water. Okay? So that’s our gauge. Our lever… controls the BTUs &, correspondingly, the gas pressure. All the way full… and shut off. Your machine’s going to have a master power switch and, typically, i’ll let our unit cool down to 250 degrees Fahrenheit before I shut the unit off. We’ve got a burner control that’s labeled “Roasting Switch.” Burner on. Burner off. “Cooling Fan” is applicable once you’ve roasted and you’re preparing to drop your charge into the roaster and you also turn on the “Cooling Stirring” – or the arms – so that the beans are agitated in the cooling tray. On… and off. “Timer Switch” I use it to pre-warm the unit before i do my first roast. I like 40 minutes. You’ve got, here in this case, 230 pounds of steel. I want this thoroughly pre-warmed so that, when i’m doing the roast, energy is not going into heating the unit… in the beans. Rather, I want this fully warmed up so that all the energy goes into the beans. And I use the timer switch… I use 40 minutes. You may find your unit is different. Airflow. I use three settings. Don’t worry about the number… Take a look at our other segment, where I use a

– cigarette lighter to indicate and so you can determine

– what’s “low,” “medium,” and “high” on your unit. And so I’ve got those mentally memorized With three settings of “low,” “medium,” and “high” controlled by the airflow. On the side of our control panel, is our RPM indicator. We’ve got a variable drum speed on the North line of roasters. So… I will use that to determine what my drum speed is for the size of charge that’s in the unit. I’ll also bump that up about 5% once I hit first crack. Now, let’s talk about the thermocouples and the probes on the North line of roasters. You’ve got four of them. We’re going to keep it very simple in this segment. First one is the bean temperature, & that’s the lower one. That drum rotates clockwise and that probe is placed to catch the bean mass at its tightest point in the tumble. Second one. Right in the middle of the drum, you’re going to have a probe in the thermocouple that’s reading your environmental temp, or your ambient temp. The third one that we have on the North line of roasters catches the exhaust temp. On the far side of the exhaust manifold… the thermocouple and the probe are going to bring back and read your exhaust temperature. And, finally, there’s a fourth probe in the reverse of the machine that catches the airflow after… it’s heated and it’s about to enter the drum. Four probes. Bean temperature: very tight mass. Second one: Environmental temperature in the center of the drum Third one: exhaust temp. Fourth one: incoming air. That’s everything I would like to, ah, go through with you on the controls on the North line of roasters. Before you begin roasting on yours… familiarize yourself with entire line of controls and roast away. We’ll see you on other segments of Roasting 101 from Mill City Roasters. Thanks for looking in.

One thought on “Roasting 101 – Machine Controls”

  1. Hey Dave – thank you again for continuing to share great information! Would you consider a video on routine maintenance for the North Roasters?

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