AEC WD 350 through WD3000 Dehumidifying Dryers - Manual (Page 24)

350-2100 cfm Dryers Chapter 4: Control Panel 23 of 58
; If one or two of a heater's three meters indicates a low reading, a burned-out heater is
likely, and should be serviced.
4-3 PLC Control
These dryers are equipped with an Omron C28K programmable logic controller (PLC).
The "brick" type PLC has 28 I/O points - 16 inputs and 12 outputs.
All inputs are 115 VAC, except for the 24 VDC input #1 from the dewpoint circuit board.
All programming and logic is factory installed on an EPROM, and cannot be modified.
A battery backup retains the programming during power failures.
Battery life is 5 years at room temperature.
If the alarm indicator blinks intermittently, replace the battery [P/N A0544701] within one
week.
4-4 Process Air Temperature Controller
Standard ACS dryers use a microprocessor based PID control for maintaining process air
temperature. The controller is a modular, self-contained unit that can slide from its mounting
housing. All parameters except for the process air setpoint are factory set and adjusted; no
field adjustment to the internal controls is normally necessary.