GRAIN DRYER & PARTS BOOK - Opico

Drying - There are two types of drying cycles: batch and automatic. Presuming there are no failures
such as loss of electrical power, exhaustion of burner fuel or mechanical problems in the dryer, the batch mode
dries the current load of grain, cools the grain if desired, and then unload the bin, stopping in the Idle state.
When it stops, the message Grain Done is present. In the automatic mode, the grain bin is first loaded and
then the grain is dried. A cool-down state may or may not occur next, depending on cool-down temperature settings.
The bin is then unloaded, followed by the dryer returning to the Fill state to start a new cycle. This will
continue until terminated by the operator or some problem occurs, including a lack of enough grain to fill the bin.
In the case of this latter event, the dryer will return to the Idle state with an appropriate message on the LCD display.
If the display is set to the status mode, the progression through the various states may be observed by
watching the messages on the LCD display.
The drying portion of the cycle progresses as follows: a 16-second Purge state is entered first during
which any unburned gas in the plenum is expelled by the dryer fan. It at the start of this period that the fan will
be activated.
After the purging time has passed, the controller will move to the Ignite state. The electric ignitor will
generate a spark and the low-flow fuel path will be opened so that fuel is supplied to the burner. This period will
continue for up to 90 seconds, if needed, during which time the burner should light.
Once ignition occurs, the controller will move to the Heat state. This is a 30 second period during which
the high-flow fuel path remains blocked. This will assure that dryers that need to heat the fuel for efficient burner
operation will have time to raise the temperature of the fuel heater.
In the previous three cases, the status display shows only the state of the controller, or Purge, Ignite
and Heat, respectively. But once the dryer reaches the drying state, the status display will alternate between the
state - Dry - and temperature information for the plenum and the grain.
When the grain reaches the preset grain temperature for dryness, the unit will move on to the Cool state
where the burner is now extinguished and the grain is cooled by ambient air supplied by the fan. The displayed
messages are similar to those in the Dry state, but the plenum temperature is omitted as the burner is extinguished.
When the cool setpoint is reached, unloading commences. If the cool setpoint and grain setpoint are
equal, the Cool state is terminated immediately after being entered and the dryer moves directly to unload.
Manual unloading can also be initiated if the operator wishes to unload in the bin without completing the
drying process. The dryer must be removed from the drying mode to do this.
Safety and Control Monitoring - A variety of sensors provide information to the controller about the
dryer's condition. These check for excessive plenum temperatures, burner flame presence or absence, air flow
through the burner, grain and plenum temperatures, the magnitude of the 12 Volt DC internal supply, grain bin
being full or empty. Some conditions are monitored continuously, while others are only checked when to do so
is vital for safe dryer operation.
Whenever an unsafe condition is detected, the controller will stop all dryer operation over which it has
control, thus returning the dryer to the Idle state. A message indicating the problem which produced the halt is
presented. Since some of these conditions may be transient, the problem may vanish by the time the operator
returns. To avoid losing the cause, the detected condition is latched on the display. The operator can clear it by
pressing any key.
Some "normal" conditions will stop the dryer as if they were failures. For example: if the controller had
been set to fill the bin, but the automatic batch mode had not been set, when the bin becomes full, the dryer will
return to the Idle state and display the message Fill Done, as well as turning the INDICATOR LIGHT on.
The OFF button may always be used to instantly remove power from all of the 12 Volt DC devices controlled
by the unit, including the burner fuel solenoids and motor contactors. The internal switching device is a
relay, thereby assuring that there are no residual currents flowing in any of the controlled elements.
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