©2025 Copeland LP.
026-1803 R13 Supervisor I&O User Guide 9 - 59
9.42.1 Learning Mode
When the application runs for the first time, it undergoes a
“Learning Mode” period to collect data on the chiller stages.
During Learning Mode, Modular Chiller Control will control
the chilled water temperature, but it will purposely cycle the
chiller stages in different combinations to measure the effect
they have on the temperature input value.
The Learning Mode lasts for several minutes. After Learning
Mode ends, the Modular Chiller will require up to 24 hours of
operation before compressor cycling is operating at
maximum efficiency. If compressor cycling seems too
frequent after 24 hours of operation, you may reduce
compressor cycling by changing the Control/Cycles
parameter.
9.42.2 The Control/Cycles Parameter
The Modular Chiller Control has one parameter with five
preset settings to allow users to alter temperature control
performance or compressor cycling frequency. The default
setting, “Moderate Control,” seeks to balance good
temperature control with efficient cycling. If tighter
control is needed, setting the field to “Tight Control” or
“Tightest Control” will increase the application’s reaction to
temperature changes, resulting in tighter control
(usually at the expense of more frequent cycling). If fewer
compressor cycles are desired, setting the field to “Less
Cycling” or “Least Cycling” will decrease the number of
cycles but also increase the amount of fluctuation in the
temperature control.
9.42.3 Compressor Control
Modular Chiller Control can utilize up to 32 compressors for
maintaining the chilled supply temperature at a user
specified setpoint. This is accomplished by either turning on
or off any of the compressors defined in the application. As
Supply Temperature rises above setpoint, compressors will
be turned ON. As Supply Temperature falls below setpoint,
compressors will be turned OFF. The Chilled Supply
Temperature sensor should be located very close to the
Compressor Control Unit so no minimal control lag is
expected to be present.
When a compressor has been shut down on an alarm, the
compressor will remain out of the active rotation until the
alarm has been cleared. Additionally, the user will have the
option of specifying that the alarmed compressor be re-tried
the next time it comes up in the rotation. To prevent damage
to a compressor, the user will have the option of specifying a
number of trips per day before the compressor is
permanently locked out. Once this condition has occurred,
the compressor alarm will require a manual reset to bring it
back into the active rotation.
The controller will monitor the Chilled Differential
Pressure and if it falls below a user specified threshold, the
controller will start to shut down compressors one at a time
based on a user specified time delay. This shutdown
operation will be suspended if the Chilled Differential
Pressure rises above a user defined setpoint.
9.42.3.1 Digital Scroll Compressor
Modular Chiller Control can also utilize a single Digital Scroll
Compressor. The assumption is that one of the Compressor
Control Modules in the system may have a digital scroll
instead of a standard scroll compressor installed. The Digital
Scroll Compressor may not be the same size as the fixed
scroll compressors. When a Digital Scroll Compressor is
defined in the application, Modular Chiller will utilize the
compressor control modules with the digital scroll at all times,
modulating the capacity of the compressor to maintain the
Chilled Supply
Temperature setpoint. All other compressor control
modules will be turned ON or OFF based on the rotation
sequence defined above. Based on this strategy, the digital
scroll compressor will have the fewest cycle counts and the
most runtime of all the compressors in the system.
9.42.3.2 Variable Frequency Drive Compressor
Modular Chiller can utilize one compressor with a variable
frequency drive. The method of control will be similar to the
digital compressor strategy. The application will continue to
allow only one variable capacity device to be defined in the
system, making the Variable Frequency Drive and Digital
compressor options mutually exclusive.
If a Variable Frequency Drive compressor is to be used and it
is a Control Techniques drive using the Modbus
communication interface, the Control Techniques Drive
association menu will support associating the drive to an
Modular Chiller.
9.42.3.3 Unequal Capacity Compressors
Optionally, Modular Chiller Control can support different
capacity compressors. When this option is selected, the
capacity of each defined compressor will be user specified.
The controller will evaluate the capacities of all the
compressors to determine the appropriate compressor to
switch on or off in order to maintain the Supply Temperature
at setpoint.
When unequal capacity compressors are defined, the
controller will not use a simple round robin approach to
switching compressors on or off (as with equal capacity
compressors) and therefore compressor runtimes may vary
significantly over time. However, for those compressors
defined with identical capacity, the algorithm will attempt to
keep both runtimes and cycle counts as even as possible.
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