This refrigeration glycol
chiller system is used to regulate the temperature of liquid in
a storage tank by controlling the starting and stopping of eight
pumps and controlling the percentage that two valves are open.
Cooling is provided by liquid Ammonia which is controlled by the
two valves and glycol is circulated through the chiller with two
of the eight pumps. Heating is controlled by the remaining pumps
in three separate systems which contain two pumps each, one of
these pumps water and the other glycol. These liquids are then
passes through the heating coils or are routed around them depending
on the current temperature.
To accomplish this task a QuickDesigner program was written
to provide the user interface and a ProWORX NxT program was written
for the PLC. The two programs are connected via Modicon Modbus
Plus. The quickDesigner program contains several screens including
screens to monitor the temperature of each of the loops, a semi-graphic
view showing the overview of the system, and pump control screens.