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
“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.
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.
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
that catches the airflow after…
it’s heated and it’s about to enter the drum.
Bean temperature: very tight mass.
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.