Controls Interface
52 ARTC-SVX005A-EN
Microprocessor Control System
PolyTherm chiller/heater models employ an all-digital data
control system to control and report key system settings
and indicators.
Master Microprocessor Controller
A microprocessor controller is used to control tasks and
automate functions. One microprocessor controller is
designated the master controller. All others are called
slave controllers. The master microprocessor controller
rotates the lead compressors every 168 system operating
hours. The master controller reads all analog and fault port
values from the slave controllers and passes these values
to the Building Automation System (BAS). This controller
must have the optional BAS card installed to connect to a
building automation system.
Slave Microprocessor Controller
In normal configuration, a slave controller controls the
single module to which it is dedicated. The distributed
design of the microprocessor controller system enables
the chiller/heater to operate in the event the master
microprocessor controller fails. The system automatically
fails-over to distributed control where each slave
controller operates its own module in the normal fashion,
but lacks the ability to rotate the lead compressor every
168 system operating hours. See Figure 34, p. 52.
Microprocessor Controller Functions
The microprocessor provides the following functions and
alarms:
• Adjustable fluid temperature set point
• Multiple stage compressor control, including
compressor rotation to provide balanced compressor
usage and wear
• Reset temperature control set point based on
decreased load
• High and low fluid temperature alarm set points
• Fluid inlet and outlet temperature
• Suction and discharge refrigeration pressures on each
refrigeration circuit
• Compressor run status
• Current alarm status
• Demand load
• Compressor run hours
• Running count of compressor starts
• Alarm logging with the time/date of the previous 1,000
alarms
• Remote start-stop input
• Dry contact for general alarm
Thermal Capacity
The thermal capacity of the chiller/heater modules is
dependent on the leaving temperature of the chilled water/
glycol mixture, maintaining a minimum flow of water
through the heat exchangers. In applications where it is
desired to operate with a lower flow rate or higher
temperature change, consult Trane technical support for
recommendations.
Electronic Controls
The PolyTherm Chiller/Heater is provided with a robust set
of controls and indicators to monitor system performance
and notify operators if problems arise. See “Operating
Principles,” p. 24 for a complete description of the
touchscreen interface.
Figure 33. PolyTherm chiller/heater touchscreen
interface panel
Figure 34. PolyTherm chiller/heater controller
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