Roasting 101 – Machine Controls

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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.


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.


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.


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.


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.


Self proclaimed "humblest man in the universe", Nick enjoys simple things like 4th century architecture remodeling and eating unripened tomatoes.