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350-2100 cfm Dryers Chapter 5: Startup, Shutdown & Operation 31 of 58
5-11 Regeneration Monitoring System Signal Processor
Dryer models 350 through 2100 have a 1/8 DIN signal processor that monitors the bleed air discharged
from the desiccant tower being regenerated. The signal processor has four programmable temperature
setpoints that, when reached, signal the PLC to cycle through the regeneration process. The PLC
interprets the outputs from the signal processor depending on the part of the regeneration process
currently underway.
The signal processor's setpoints are factory set for efficient operation in most situations. The
manufacturer does not recommend changing the setpoints indiscriminately, but persons knowledgeable
of the processing system may fine tune the setpoints for decreased energy consumption.
LL Setpoint - Low Regeneration Alarm Setpoint - 130
°
F
This setpoint alerts the PLC and operator to possible regeneration heater problems. If this bleed air
temperature is not reached within 30 minutes of the regeneration heaters being energized, the Low
Regen Air Temp Alarm lights. The light will go out automatically when the setpoint is reached. The
alarm can indicate burnt out regeneration heaters, or an extremely moist desiccant bed.
L Setpoint - Regeneration Blower Shutdown Temp - 160
°
F
After a desiccant tower has been regenerated, the regeneration blower continues to cool the desiccant
until this setpoint is reached. The signal processor informs the PLC, and the PLC shuts down the
regeneration blower to prevent loading the regenerated bed with ambient moisture.
H Setpoint - Optional Closed Loop Regeneration Cool Down Temp - 250
°
F
This setpoint output is used on dryers equipped with optional closed loop regeneration cool down.
When this setpoint is reached, the output signals the PLC to shift the Wye valve in this device's
aftercooler and the cooling water valve to close loop and cool the regeneration air. The very dry
regeneration bleed air is directed back into the aftercooler where it is cooled to about 150°, and then
back into regeneration blower inlet. This ensures that no moisture will be added to the desiccant bed
until it goes back on line.
HH Setpoint - Heater Cut Off Temp - 300
°
F
This setpoint is the temperature at which the PLC is signaled to shut off the regeneration heaters
because the desiccant is dry, and begin the cool down process.
Raising this setpoint will not significantly improve dryer performance, but merely increase energy
consumption.
Basic information is listed below. For more detailed information, refer to the processor manual shipped
with the dryer.
To change the Regeneration Monitor System Setpoints:
• Press
until the LED above the parameter to be changed (LL, L, H, or HH)
is lit. The number value displayed is the selected parameter's current set point.
•
• Within 5 seconds, press
until the digit to be changed blinks.
• Press
until the desired number value is displayed in that digit position.