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Operating Procedures
Figure 14. Microprocessor controller
A master 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
master 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.
Client and Server Controllers
The distributed microprocessor control system enables all
server modules to operate independently in the event that
the client microprocessor controller fails. All chiller/heater
safeties including temperature set point, refrigerant
Figure 15. Typical controller network
28
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 server controller controls the
single module to which it is dedicated.
The server controller monitors key performance
parameters for its module and sends real-time
information to the client controller. The client controller
monitors the performance of the chiller/heater, activating
and deactivating modules as needed to maintain the
leaving water temperature for the chiller/heater.
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ARTC-SVX005A-EN
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