Grain Systems PNEG-1935 - Manual (Page 49)

6. Moisture Control Options
PNEG-1935 Vision Hybrid for Portable Dryers 49
Here is an example of how to calculate the Dry Time:
Let’s say we have a 1/2-1/2 split dryer, so N will equal two. The wet grain has a moisture content of 21%
and we want to dry it to 15%. We will use 5 minutes as our initial guess for the MPP. The Cool Time is set
for 20 minutes and the Unload Time is set for 10 minutes. So our variables are as follows:
Now that we have calculated the initial Dry Time, let’s use it. Stop the dryer if it is running. Once the dryer
is stopped, press and hold the Stop button on the control panel for 10 seconds. This tells the dryer to
calculate the MPP using the Dry Time that is entered by the user, rather than calculating normally. This
should be done the first time you run this process or when you are changing grains and know that the MPP
is not the same.
The MPP is constantly being changed to narrow down the ideal MPP value. By holding the “Stop” button
as mentioned above, it resets the MPP variable. So say you run the dryer for an entire day and shut it off
for the night. This day you calculated the Dry Time using the calculation above to give the control a starting
point. The next day you come out to the dryer, the MPP value will carry over from the day before and start
at that value, unless you press and hold the “Stop” button.
Enter the Dry Time that you calculated (2:30 minutes in our example above), Cool Time and Unload Time.
Press the Start button to begin the process. Keep in mind the controller will not adjust the Dry Time for the
first couple of batches. The number of batches it takes before it assumes control depends on the number
of plenum splits. If you have a 1/3-2/3 split, it will not start changing until the fourth batch.
A “Max Grain Temp” safety is available for this scheme. By enabling this feature, the dryer will shutdown
and issue a warning if the grain temperature exceeds the “Max Grain Temp” value.
ΔMC = Incoming M/C - M/C setpoint = 21-15 = 6
MPP = 5 minutes
N = 2
Cool Time = 20 minutes
Unload Time = 5 minutes
Now let’s put the values into the equation:
Dry Time =
(ΔMC * MPP) - Cool Time - Unload Time
N
Dry Time =
(6 * 5)-20-5
2
Dry Time = = 2 minutes 30 seconds
5
2