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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

[email protected]

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
http://ecd-00014u-r08-mcc-operation-overview.pdf/http://ecd-00014u-r08-mcc-operation-overview.pdf/http://ecd-00014u-r08-mcc-operation-overview.pdf/http://ecd-00014u-r08-mcc-operation-overview.pdf/http://ecd-00014u-r08-mcc-operation-overview.pdf/http://ecd-00014u-r08-mcc-operation-overview.pdf/http://ecd-00014u-r08-mcc-operation-overview.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-procedures.pdf/http://ecd-00014u-r08-mcc-procedures.pdf/http://ecd-00014u-r08-mcc-procedures.pdf/http://ecd-00014u-r08-mcc-procedures.pdf/http://ecd-00014u-r08-mcc-procedures.pdf/http://ecd-00014u-r08-mcc-procedures.pdf/http://ecd-00014u-r08-mcc-procedures.pdf/http://ecd-00014u-r08-mcc-procedures.pdf/http://ecd-00014u-r08-mcc-procedures.pdf/http://ecd-00014u-r08-mcc-procedures.pdf/http://ecd-00014u-r08-mcc-procedures.pdf/http://ecd-00014u-r08-mcc-procedures.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-functionality.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-userinterface.pdf/http://ecd-00014u-r08-mcc-operation-overview.pdf/http://ecd-00014u-r08-mcc-operation-overview.pdf/http://ecd-00014u-r08-mcc-operation-overview.pdf/http://ecd-00014u-r08-mcc-operation-overview.pdf/http://ecd-00014u-r08-mcc-operation-overview.pdf/http://ecd-00014u-r08-mcc-operation-overview.pdf/http://ecd-00014u-r08-mcc-operation-overview.pdf/


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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

Danfoss Turbocor Compressors Inc. 1

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


ECD-00014-U-R09

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


ECD-00014-U-R09

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


ECD-00014U-R09

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

Danfoss_Turbocor_Inc.Carel_ControllerVer.0.0.110


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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

Danfoss_Turbocor_Inc.Carel_Controller

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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

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