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MULTIPLE COMPRESSOR CONTROLLER USERS MANUAL
Danfoss Turbocor Compressors Inc. ECD-00014-U-R09
January 2008
Multiple Compressor Controller
Featuring ModBus Communications
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Danfoss Turbocor Compressors Inc.
ECD-00014-U-R09
Proprietary Notice
This publication contains information proprietary and confidential to Danfoss Turbocor Compressors Inc. (DTC). Any
reproduction, disclosure or unauthorized use of this publication is expressly prohibited without written approval from DTC.
DTC reserves the right to make changes without notice in product or component design as warranted by evolution in user
needs or progress in engineering or manufacturing technology.
DTC has exercised its best efforts to ensure that the information contained in this manual is correct. However, no warranty of
reliability or accuracy is given with respect to the information and DTC shall not be responsible or liable for the correctness
or suitability of the information or for any error or omission. If you encounter any difficulty in using this manual, please
forward your query to Danfoss Turbocor Compressors Inc. or its authorized sales agent.
All brand names and product names used in this manual are trademarks, registered trademarks, or trade names of their
respective holders.
For product support issues, contact:
Product Support
product_support@turbocor.com
Danfoss Turbocor Compressors Inc.
1769 E. Paul Dirac Drive
Tallahassee, FL 32310
USA
Telephone: (850) 504-4800
Fax: (850) 575-2126
www.turbocor.com
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Contents
Danfoss Turbocor Compressors Inc. iECD-00014-U-R09
1 Multiple Compressor Controller - Overview 1Introduction 1Application 1
Display Features 1Communication Features 1
Environment Constraints 1Ordering Details 1
2 Multiple Compressor Controller - Interface 2Interface Introduction 2
Hardware I/O Interface Controls 2Controller Interlocks 2
Communications Interfaces 2Carel Modbus Gateway 2BMS Network Modbus Protocol 2
3 Multiple Compressor Controller - Functionality 3
General Control Strategy 3Application Setup Types 3Freeze Control 3Parallel Control Mode 3Staged Control Mode 4
Staged Control Considerations 4Minimum Off Timers 4
Alarms 4
4 Multiple Compressor Controller - Operating Procedures 5Introduction 5PLC Control Panel Operations 5
Alarms 5General Alarms 5System Alarms 5
Appendix A Carel Control Panel Display 6PLC Overview 6
Selection Screens 6Interlock Messages 8
Interlock Message options 8Viewing Circuits 8
Circuit Temperature Status 8
Circuit Pressure Status 9Condenser Fans Status 9Compressor Status 9
System Setup 10Analog Input Configuration 10Compressor Configuration 11Compressor Configuration 11
Configuration Screens 12Evaporator Configuration Screens 12
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Contents
Danfoss Turbocor Compressors Inc. iiECD-00014-U-R09
Controller Stage Settings 14Condenser Configuration 14Modbus Settings 15Miscellaneous Configuration Screens 16
Compressor Circuit IDs 16Appendix B Drawings 18
Appendix C Inputs/Outputs 19
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Multiple Compressor Controller - Overview
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ECD-00014-U-R09
1 Multiple Compressor Controller - Overview
1.1 Introduction
This manual describes the functionality and operation
of the Multiple Compressor Controller (MCC). The
controller features generic software that is
configurable for use with either the basic I/O or the
expanded I/O hardware platforms. In its expanded
form, the controller can accommodate up to six
compressors.
NOTE
While the controller algorithm is designed to
maintain desired set point with minimal varia-
tions, it could swing depending on the configura-
tion settings and the system characteristics.
1.2 Application
The MCC performs the following primary functions:
Controls the entire chiller/system and some auxiliary
devices
Performs monitoring, analysis and fault display.
1.2.1 Display Features
The controller features a remote semi-graphic display
with the ability to:
View the compressor status and detailed information
View the input and output status
View and adjust set points
View and adjust timers where applicable
Acknowledge and reset warnings and alarms
View the alarm history
Configure the pre-programmed software to suit the
specific application
Enable and/or disable inputs and/or outputs that are
optional
1.2.2 Communication Features
The MCC communicates with the compressors via
ModBus, which enables it to read various parameters
and control the compressors by writing to certain
parameters. It can act as the centralized controller for
systems with one to six compressors.
1.2.3 Environmental Constraints
The following information provides recommended
environmental conditions.
1.3 Ordering Details
The following information provides the ordering
details for this controller.
Environment Range
Storage -20C to 60C*
Operation -10C to 60C*
* Relative humidity less than 80%, non-condensing
Table 1 Temperature Range
Description Details
Part Description Retrofit Controller Kit
Part Number 111047
Notes Kit includes Turbocor Specific
software, temperature sensors,
remote semi-graphic screen,
connector kit, and 1.5 meter (5 feet)
RJ-12 communication cable.
Table 2 Ordering Details
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Multiple Compressor Controller - Interface
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2 Multiple Compressor Controller - Interface
2.1 Interface Introduction
The latest model of the Carel pCO series is used, the
Pco3, which enables very fast communication with the
compressor by means of the serial port over ModBus.
2.1.1 Hardware I/O Interface Controls
Each TT300/TT400 compressor is equipped with the
following I/O points for controls and interfacing:
Interlock (voltage-free contact), compressor start/
stop, 1 * DI
Numerous parameters including demand, which is
an input parameter modulating the compressor
capacity between 0 - 100%, 1 * RS485 Port.
(1) Status (SPD contact), generic compressor faultstatus, 1* DO
(2) Compressor run status, based on user-selectable
motor RPM, 1*DO
For a detailed list and typical wiring of all I/Os
available on the Turbocor compressor, refer to
Drawings (see APPENDIX B). Also refer to pCO3
manual, document no. 050003290, which can be
found at http://carelusa.com/pco3_literature.htm.
2.1.2 Controller Interlocks
The following inputs are connected to the Multiple
Compressor Controller:
Remote on/off switch
Evaporator flow switch
Condenser water flow switch (water-cooled unit
only)
Cooling call
All of these inputs enable/disable the controller. Refer
to electrical schematics for input configuration.
NOTE
All other inputs that are not used must be bridged.
To ensure protection against system freeze-ups or
other major failures, at least one external safety
interlock must be connected to the Multiple
Compressor Controller at all times. All external
safety and system interlocks can be wired in
series, if required.
2.2 Communications Interfaces
The Multiple Compressor Controller (MCC) supports
upstream communications to a Building Management
System (BMS) through a Carel Modbus protocol.
2.2.1 Carel Modbus Gateway
The MCC Carel Modbus requires a relevant gateway
card in order to establish a communications link to theBMS Network, a gateway interface card for the MCC
Carel Modbus is available from Carel company,
contact Carel technical support (www.carel.com).
NOTE
The purchase and installation of a Carel Modbus
interface card by a third party company to enable
communications to a BMS Network may be
required.
2.2.2 BMS Network Modbus Protocol
For BMS Networks connected to the MCC Carel
Modbus requires the BMS network can communicate
via Modbus protocol.
For BMS Networks utilizing Modbus Protocol, no
protocol conversion is required.
For BMS Networks connected to the MCC Carel
Modbus via a non Modbus protocol (such as LON or
BacNet) an interface card is required to convert
communications from the MCC Carel Modbus
protocol to the BMS communications protocol.
NOTE
The purchase and installation of a protocol con-
version interface card by a third party company
may be required. See your BMS administrator for
interface card parameters and your BMS supplier
for the appropriate interface card.
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Multiple Compressor Controller - Functionality
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3 Multiple Compressor Controller - Functionality
3.1 General Control Strategy
The Multiple Compressor Controller (MCC) is
configurable to control either leaving or entering
chilled-water temperature, depending on the
application requirements.
In principle, the demand to the compressor(s) is
determined by the Demand Generator*. The output of
the Demand Generator is based on the difference
between the setpoint and the controlled value. In
addition, the control strategy is based on system
demand (Low Load Control). When the main
application is controlling leaving chilled water
temperature, and the entering chilled water
temperature drops below a certain value, the setpoint
is shifted upwards to compensate for a lower load.Similarly, when the main application is controlling
entering chilled water temperature, and the leaving
chilled water temperature drops below a certain value,
the setpoint is shifted upwards to compensate for a
lower load.
* The Demand Generator is a proportional integral (PI) controller based
on the SSTEP2 macro block from Carel. Proportional band and
integral time adjustments can be made through the Band, Update, and
Max. Change parameters.
NOTE
While the controller algorithm is designed tomaintain desired set point with minimal varia-
tions, it could swing depending on the configura-
tion settings and the system characteristics.
3.2 Application Setup Types
The software setup is largely generic. Sensors can be
connected for entering and leaving chilled water
temperatures in all applications.
When the system is set up for a water-cooled chiller
application, additional sensors can be connected to
display the entering and leaving condenser watertemperatures.
In an air-cooled application, there is an option to
connect an outside air temperature sensor.
The appropriate screens are activated according to the
specific set-up. There are also two options for
condenser fan switching: one is where the fans are
switched locally (in steps) with pressure switches
based on head-pressure and the other is where a head-
pressure transducer is connected to the controller, and
the fans are switched by the controller in up to three
steps per compressor.
3.3 Freeze Control
Regardless of using leaving or entering water control,
when the leaving chilled water temperature drops
below the leaving chilled water freeze point, the
demand drops to zero and an alarm is generated. The
compressors can only start again after this alarm is
reset, and when the leaving chilled water is above the
setpoint.
Freeze control is implemented by monitoring the
leaving water temperature at the MCC. The leavingwater temperature can be monitored at either the
temperature sensor input at the MCC (B2 default) or
via the Modbus from any compressor. As an additional
safeguard, interlocks are used to signal the MCC when
there is insufficient pump flow or condenser leaving
water flow. The interlock circuit is connected to a
digital input (ID1-14) of the MCC.
3.4 Parallel Control Mode
With parallel control, all operating compressors are
shut down. After their IGVs are reset, they are
restarted along with an additional compressor that waspreviously off. The compressors ramp up together
with the load equally distributed across all of them.
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Multiple Compressor Controller - Functionality
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3.5 Staged Control Mode
In staged control, the running compressors are
unloaded until they reach a specific pressure ratio, as
defined in the user interface. An additional
compressor that was previously off is started. When
the compressor attains the same pressure ratio as the
other compressors, the compressors ramp up together
with the load equally distributed across all of them.
This mode can give better capacity control of the
system, as it harnesses the ability for a single
compressor to be operating under really low load
conditions, and you are not restricted by the minimum
point of all compressors combined.
The 'System demand' (the output from the Demand
Generator) varies from 0-100 percent based on the
difference between the setpoint and the controlled
value (e.g. ChW temperature).
As the system demand increases, the demand to the
first compressor also increases. Once the compressor
is no longer able to meet the system demand within a
certain time period, the controller will begin to stage
on the second compressor. This will involve the
running compressor unloading to facilitate the
optimum system conditions needed to start the next
compressor. This process will occur for each
subsequent compressor that is in the system.
As the system demand decreases from 100 percent, thecontroller will unload all the compressors in parallel
until the system demand has dropped below the
minimum combined capacity of the running
compressors. At this point, the controller will begin to
shut down compressors (one at a time), and then allow
the remaining compressors to increase their capacity
as needed to match the system demand.
3.5.1 Staged Control Considerations
When one compressor is running at a demand below
the requested demand from the controller, the secondone will start. Theoretically, after they have been
started, both compressors will then approximately
operate on half of the initial capacity. The demand to
the initial compressor(s) will drop (e.g. from 100
percent to 50 percent), while the second will be started
with a 50-percent demand.
The bandwidth between the actual demand and the
requested demand on a compressor can be configured
by the user to allow more or less time for system
stabilization in the staging sequence of the
compressors.
It is important to recognize, however, that thecompression ratio of the system needs to reduce to an
acceptable level to allow the efficient and safe starting
of the second or subsequent compressors. This time
interval may vary depending on the conditions of the
system.
The hysteresis for switching one, two or three (groups
of) compressor(s) in this example is set to 5 percent.
However, it is a parameter that can be set via Level 2
user access for tuning purposes.
At start-up, the integral term of the Demand Generator
is switched off for 90 seconds to prevent overshootbecause the compressors themselves have a ramp-up
time.
3.5.2 Minimum Off Timers
Minimum Off Time is the time the compressor will
stay off after the demand to that compressor has
reached zero. The Minimum Off Timers are to prevent
any unwanted switching of compressors while the
compressors are ramping up to satisfy an increasing
demand.
For staged control, these timers operate on theindividual demands to the compressors.
For parallel control, the timers operate on the
combined demand.
3.6 Alarms
Each compressor can indicate a fault via Modbus
communication. If a compressor fails, the demand to
that compressor will go to zero and a generic fault will
appear on the controller display. After the fault on the
compressor has been resolved, the fault message onthe controller can be reset.
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Multiple Compressor Controller Operating Procedures
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4 Multiple Compressor Controller Operating Procedures
4.1 Introduction
The controller is designed to run the compressor at
various motor kW conditions. The setpoint is set at the
PLC control panel, which also controls and monitors
other functions in the chiller and acts as an interface
between the chiller and the compressor. Alarms and
compressor status can be read from the PLC screen.
Refer to PLC Control Panel (see Figure 1).
Figure 1 PLC Control Panel
4.2 PLC Control Panel Operations
Starting the PLC Control Panel
1. Ensure all interlocks are closed.
2. Press Esc until the main menu appears.
Figure 2 Main Menu Screen3. Using the button, select SYSTEM ON/OFF.
4. Press the button to view the System Status screen.
Press the button again to select the compressor on/
off option.
5. Press the or button to switch the compressors
on or off. Press the button. If the compressor is
switched on, it will ramp up according to the system
demand to maintain the setpoint; otherwise, it will shut
down.
6. Press Esc to return to the main menu.
Monitoring the Conditions
1. Press Esc until the main menu appears.
2. Select SYSTEM STATUS and press the button. System status such as water temperature
and compressor running time can be viewed.
Figure 3 System Start-Up Screen
4.3 Alarms
4.3.1 General Alarms
The PLC monitors the status of the temperature inputs.
Disconnecting any one of the three temperature
sensors trips an alarm and the unit will stop.
4.3.2 System Alarms
The following alarms can be present:
Danfoss_Turbocor_Inc.Carel_ControllerVer.0.0.110
Compressor
faultGenerated by the compressor if
there is an internal alarm.
Pump failure The pump is not running due to a
thermal overload, or it is not
switched on.
Condenserwater flow
too low
The condenser water flow switch
detects a low-flow condition.
Compressornot powered
on
The compressor is not running due
to a fault, or it is not switched on.
High
condenser
water
temperature
This alarm is triggered when the
condenser water temperature sensor
registers a temperature above its
trip setpoint (40C).
Table 3 System Alarms
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APPENDIX A Carel Control Panel Display
A.1 PLC Overview
This section describes the various screens that are
available on the PLC control panel display.
A.1.1 Selection Screens
Monitoring screens allow you to view the system data
while the system is running.
Navigating the Start-Up Screen
Upon initial power-up, the start-up screen will appear
(see Figure A-1).
Figure A-1 Start-Up Screen
1. Record Carel Controller version number (see
Figure A-1).
2. Simultaneously press alarm button and
button and hold for approximately four seconds.
3. A blinking cursor will appear (see Figure A-2).
Use arrows to choose System Info and press
button.
Figure A-2 Controller Information Screen
4. Ensure bios is above 4.00 (see Figure A-3).
5. Record BOOT and BIOS info. When finished,
press Esc. Record Carel cont VER 0.0.110.
6. Press Esc button to return to start-up menu.
Figure A-3 System Info Screen
7. To verify if controller is set up to log data, performstep 2 again. Use the up and down arrow keys to
move > symbol in front of LOG DATA (see
Figure A-2), then press .
8. If there is no log data, the following screen
appears (see Figure A-4):
Figure A-4 No Log Data Screen
9. Selecting OTHER INFORMATION brings up
the ID number (see Figure A-5).
Figure A-5 Other Information Screen
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10. Press the Prg button. To System Setup will
display (see Figure A-6).
Figure A-6 System Info Screen
11. Press the Esc button to go to System Info. To
System Monitor will display.
Navigating the System ConfigurationScreen
Figure A-7 System Configuration Screen12. Press the button To Continue Setup, to will
display, System Configuration Menu (see Figure
A-18).
13. Press the Esc button to View System will
display, System Info Screen (see Figure A-8).
Navigating the System Info Screen Screen
Figure A-8 System Info Screen14. Press the '' button to go To System Setup, will
display, System Configuration Screen (see
Figure A-7).
15. Press the Prg button to Go To System Info,
will display either:
16. an interlock status screen will display, Interlock
Status Messages (see Figure A-9), or
17. an interlock status screen will display, View
Circuit # Selector (see Figure A-10), or
The following are abbreviations used in displays.
System_Info:
System_Configuration:
_____To_Continue_Setup--->
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A.2 Interlock Messages
The following screen is a message, telling that an
Interlock to the Carel controller is open.
Figure A-9 Interlock Status Messages
The following table details the screens fields.
A.2.1 Interlock Message options
Close the Interlock Item, through systemconfiguration.
Press the '' button to access the View Circuit #Selector (see Figure A-10).
Press the Prg button to access the SystemConfiguration Screen (see Figure A-7).
Press the Esc button to access the SystemInfo Screen (see Figure A-8).
A.3 Viewing Circuits
The following screen provides the option to choose
which circuit to monitor. For Typical I/O Wiring for
Multi-Compressor Controller (see Figure B-1).
Figure A-10 View Circuit # Selector
Selecting a View Circuit
1. Scroll using '' or '' buttons to select a circuit to
monitor.
View Circuit # (Circuits 1-6)2. Press button to view circuit.
3. View Circuit Screen Details (see details by type)
Circuit # Readings (see Figure A-11)
Circuit Pressure Readings (see Figure A-12)
Condenser Fans Voltage (see Figure A-13)
Condenser Fans Setpoints (see Figure A-14)
Compressor # Status (see Figure A-15)
A.3.1 Circuit Temperature Status
This screen represents the current status of the system.
Interlock
Open The screen will appear only if the
interlock is open. Interlock is open
when the Interlock input has 24Volts present.
The screen would not appear, when
the interlock is closed.Remote
_On/OffSee Miscellaneous System (see Figure
A-33) "Remote On/Off ch#" to check
which channel is set as the remote On/
Off channel.
Evaporator
_#
Indicates that interlock on evaporator
side, circuit #, is opened. See
Evaporator Control (values represent
generic defaults) (see Figure A-25) to
check channel settings.
Condenser
_#
Indicates that interlock on condenser,
circuit #, is opened. See Condenser #
Interlock Status (see Figure A-31) to
check channel settings.
Interlock_Open!
Remote_On/Offopen!
Interlock_open!
Evaporator_#interlock_open!
Interlock_open!
Condenser_#interlock_open!
_>View_Circuit_1