AK-PC781_eng.pdf

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Design Guide
Capacity controller with
heat recovery function
AK-PC 781
ADAP-KOOL® Refrigeration control systems
Contents
1. Introduction .............................................................................3
Application.................................................................................................. 3
Principles...................................................................................................... 4
2. Design of a controller ..............................................................7
Module survey ........................................................................................... 8
Common data for modules .................................................................10
Controller ...........................................................................................12
Extension module AK-XM 101A .................................................14
Extension module AK-XM 102A / AK-XM 102B .....................16
Extension module AK-XM 103A .................................................18
Extension module AK-XM 204A / AK-XM 204B .....................20
Extension module AK-XM 205A / AK-XM 205B .....................22
Extension module AK-XM 208C ................................................24
Extension module AK-OB 110 ....................................................26
Extension module AK-OB 101A..................................................27
Extension module EKA 163B / EKA 164B / EKA 166 ............28
Graphic display AK-MMI ...............................................................28
Power supply module AK-PS 075 / 150 / 250 ........................29
Communication module AK-CM 102 .......................................30
Preface to design ....................................................................................32
Functions............................................................................................32
Connections ......................................................................................33
Limitations .........................................................................................33
Design of a compressor and condenser control .........................34
Procedure: ..........................................................................................34
Sketch ..................................................................................................34
Compressor and condenser functions ....................................34
Connections ......................................................................................35
Planning table ..................................................................................37
Length .................................................................................................38
Linking of modules .........................................................................38
Determine the connection points ............................................39
Connection diagram ......................................................................40
Supply voltage ................................................................................42
Ordering .....................................................................................................43
3. Mounting and wiring.............................................................45
Mounting ...................................................................................................46
Mounting of analog output module ........................................46
Mounting of extension module on the basic module .......47
Wiring..........................................................................................................48
4. Configuration and operation ................................................51
Configuration ...........................................................................................52
Connect PC ........................................................................................52
Authorization....................................................................................54
Unlock the configuration of the controllers ..........................55
System setup ....................................................................................56
Set plant type ...................................................................................57
Set control of compressors ..........................................................58
Set oil management .......................................................................61
Setup control of condenser fans ...............................................63
Setup control of high pressure...................................................65
Setup control of receiver pressure ............................................66
Setup control of heat recovery..................................................67
Setup Display ....................................................................................70
Setup Functions for General purpose......................................71
Separate thermostats.............................................................72
Separate pressostats ..............................................................72
Separate voltage signals .......................................................73
Separate alarm inputs ............................................................73
Separate PI functions .............................................................74
Configuration of inputs and outputs .......................................75
Set alarm priorities..........................................................................77
Lock configuration ..........................................................................79
Check configuration.......................................................................80
Check of connections ............................................................................82
Check of settings.....................................................................................84
Schedule function ..................................................................................86
Installation in network ..........................................................................87
First start of control ................................................................................88
Start the control...............................................................................89
Manual capacity control ...............................................................90
5. Regulating functions .............................................................91
Suction group ..........................................................................................92
Controlling sensor selection .......................................................92
Reference ...........................................................................................93
Capacity control of compressors ...............................................94
Capacity distribution methods ...........................................96
Power pack types – compressor combinations ............97
Compressor timers ................................................................101
The capacity from the digital scroll compressor ........101
Load shedding ........................................................................102
Cascade systems – coordination and injection ..........103
Injection ON ............................................................................105
Liquid injection in suction line .........................................106
Safety functions .............................................................................106
Oil management............................................................................108
Condenser ...............................................................................................110
Capacity control of condenser .................................................110
Reference for condensing pressure ........................................110
Capacity distribution ...................................................................112
Step regulation ......................................................................................112
Speed regulation ..................................................................................112
Condenser couplings ...................................................................113
Safety functions for condenser ................................................113
EC motor...........................................................................................113
CO2 transcritical system and heat recovery ........................114
Circuit for heat recovery or hot tap water ....................115
Circuit for recovery for heating.........................................116
Circuits for control of CO2 gas pressure ........................119
Receiver control .....................................................................121
Parallel compression ............................................................122
General monitoring functions .........................................................124
Miscellaneous ........................................................................................126
Appendix A – Compressor combinations and coupling pat-
terns ...........................................................................................................130
Appendix B - Alarm texts ...................................................................136
Appendix C - Recommended connection - AK-PC 781 ...........138
2
Capacity controller
RS8GG602
©
Danfoss
2015-03
AK-PC 781
1. Introduction
Application
AK-PC 781 is complete regulating units for capacity control of
compressors and condensers in refrigeration systems. The con-
troller is with oil management, heat recovery function and CO2
gas pressure control.
In addition to capacity control the controllers can give signals to
other controllers about the operating condition, e.g. forced clos-
ing of expansion valves, alarm signals and alarm messages.
Examples
Traditional capacity control
SW = 4.5x
Booster control with 2 controls
The controller’s main function is to control compressors and
condensers so that operation all the time takes place at the
energy-optimum pressure conditions. Both suction pressure
and condensing pressure are controlled by signals from pressure
transmitters.
Capacity control can be carried out by suction pressure P0, media
temperature S4 or separate control pressure Pctrl (for cascade).
Among the different functions are:
- Capacity control of up to 8 compressors
- Up to 3 unloaders for each compressor
- Oil management. Either shared or individual for all of the com-
pressor's oil valves. Receiver pressure control.
- Speed control of one or two compressors
- Up to 6 safety inputs for each compressor
- Option for capacity limitation to minimize consumption peaks
- When the compressor does not start, signals can be transmitted
to other controllers so that the electronic expansion valves will
be closed
- Regulation of liquid injection into suction line
- Start/stop of liquid injection in heat exchanger (cascade)
- MT/LT - coordination between controllers in cascade control
- Safety monitoring of high pressure / low pressure / discharge
temperature
- Capacity control of up to 8 fans
- Floating reference with regard to outside temperature
- Heat recovery function
- CO2 gas cooler control and receiver control
- Parallel compression on transcritical CO2 system
- Step coupling, speed regulation or a combination
- Safety monitoring of fans
- The status of the outputs and inputs is shown by means of light-
emitting diodes on the front panel
- Alarm signals can be generated via data communication
- Alarms are shown with texts so that the cause of the alarm is
easy to see.
- Plus some completely separate functions that are totally inde-
pendent of the regulation – such as alarm, thermostat ,pressure
and PI-regulating functions.
(For pure booster control without MT cooling, the intermediate pressure
must be connected to the receiver to prevent Pmin and Pmax cut-outs
during the start-up).
Heat recovery functions, controlling the condensing pressure and
receiver pressure of a CO2 plant
AK-PC 781
Capacity controller
RS8GG602
©
Danfoss
2015-03
3
Principles
The great advantage of this series of controllers is that it can be
extended as the size of the plant is increased. It has been devel-
oped for refrigeration control systems, but not for any specific
application – variation is created through the read-in software and
the way you choose to define the connections.
It is the same modules that are used for each regulation and the
composition can be changed, as required. With these modules
(building blocks) it is possible to create a multitude of various
kinds of regulations. But it is you who must help adjusting the
regulation to the actual needs – these instructions will assist you
to find your way through all the questions so that the regulation
can be defined and the connections made.
Advantages
• The controller’s size can “grow” as systems grow
• The software can be set for one or more regulations
• Several regulations with the same components
• Extension-friendly when systems requirements are changed
• Flexible concept:
- Controller series with common construction
- One principle – many regulation uses
- modules are selected for the actual connection requirements
- The same modules are used from regulation to regulation
Controller
Extension modules
Top part
Bottom part
The controller is the cornerstone of the regulation. The module has inputs and
outputs capable of handling small systems.
• The bottom part – and hence the terminals – are the same for all controller types.
• The top part contains the intelligence with software. This unit will vary according
to controller type. But it will always be supplied together with the bottom part.
• In addition to the software the top part is provided with connections for data
communication and address setting.
If the system grows and more functions have to be controlled, the regulation can be
extended.
With extra modules more signals can be received and more relays cut in and out –
how many of them – and which – is determined by the relevant application.
Examples
A regulation with few connections can
be performed with the controller module
alone
If there are many connections one or more exten-
sion modules have to be mounted
4
Capacity controller
RS8GG602
©
Danfoss
2015-03
AK-PC 781
Direct connection
Setup and operation of an AK controller must be accomplished via
the “AK-Service Tool” software program.
The program is installed on a PC, and setup and operation of
the various functions are carried out via the controller’s menu
displays.
Displays
The menu displays are dynamic, so that different settings in one
menu will result in different setting possibilities in other menus.
A simple application with few connections will give a setup with
few settings.
A corresponding application with many connections will give a
setup with many settings.
From the overview display there is access to further displays for
the compressor regulation and the condenser regulation.
At the bottom of the display there is access to a number of general
functions, such as “time table”, “manual operation”, “log function”,
“alarms”, and “service” (configuration).
Network linking
The controller can be linked up into a network together with other
controllers in an ADAP-KOOL® refrigeration control system. After
the setup operation can be performed at a distance with, say, our
software program type AKM.
Users
The controller comes supplied with several languages, one of
which can be selected and employed by the user. If there are sev-
eral users, they may each have their choice of language. All users
must be assigned a user profile which either gives access to full
operation or gradually limits the operation to the lowest level that
only allows you “to see”.
Language selection is part of the service tool settings.
If the language selection is not available in the service tool for the
current regulator, English texts will be displayed.
External display
An external display can be fitted in order for P0 (Suction) and Pc
(Condensing) readings to be displayed.
A total of 4 displays can be fitted and with one setting it is pos-
sible to choose between the following readings: suction pressure,
suction pressure in temperature, Pctrl, S4, Ss, Sd, condenser pres-
sure, condenser pressure in temperature, S7 gas cooler tempera-
ture, hot tap water at heat recovery and heat exchanger tempera-
ture at heat recovery.
A graphical display with control buttons can also be fitted.
AK-PC 781
Capacity controller
RS8GG602
©
Danfoss
2015-03
5

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