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Figure 13.
Microprocessor controller
A primary controller is used to control and coordinate
the functioning of all the modules that make up the
chiller/heater unit. For units consisting of more than a
single chiller/heater, each module has its own
controller. The primary microprocessor controller has
built-in BACnet MSTP and Modbus RTU capabilities.
An optional card must be installed to connect to a BAS
using BACnet IP, Modbus IP, or LonWorks.
Controllers
The distributed microprocessor control system enables
all secondary modules to operate independently in the
event that the primary microprocessor controller fails.
All chiller/heater safeties including temperature set
point, refrigerant pressures, and freeze protection are
preserved. The distributed microprocessor control
programming only lacks the ability to rotate the lead
compressors which typically occurs every 168
compressor operating hours.
In a normal configuration, a secondary controller
controls the single module to which it is dedicated.
The secondary controller monitors key performance
parameters for its module and sends real-time
information to the primary controller. The primary
controller monitors the performance of the chiller/
heater, activating and deactivating modules as needed
to maintain the leaving water temperature for the
chiller/heater.
Figure 14.
Typical controller network
Operating the Microprocessor
The touchscreen interface panel is ready to use when it
is connected to the Ethernet switch and chiller/heater
power is ON.
Upon initial startup, the status line will indicate that the
chiller/heater is OFF. Press and hold the ON/OFF button
on the touchscreen interface panel; for few seconds to
