Danfoss ADAP-KOOL AK-PC 781 Guide

Capacity controller with
heat recovery function
AK-PC 781
Design Guide
ADAP-KOOL®Refrigeration control systems

2 Capacity controller RS8GG602 © Danfoss 2015-03 AK-PC 781
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. Conguration and operation................................................51
Conguration...........................................................................................52
Connect PC........................................................................................52
Authorization....................................................................................54
Unlock the conguration 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
Conguration of inputs and outputs.......................................75
Set alarm priorities..........................................................................77
Lock conguration..........................................................................79
Check conguration.......................................................................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
CO2transcritical 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

AK-PC 781 Capacity controller RS8GG602 © Danfoss 2015-03 3
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.
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 dierent 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.
Examples
Traditional capacity control
1. Introduction
Booster control with 2 controls
Heat recovery functions, controlling the condensing pressure and
receiver pressure of a CO2 plant
SW = 4.5x
(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).

4 Capacity controller RS8GG602 © Danfoss 2015-03 AK-PC 781
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 specic
application – variation is created through the read-in software and
the way you choose to dene 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 nd your way through all the questions so that the regulation
can be dened 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
Top part
Extension modules
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
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.
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.
Examples

AK-PC 781 Capacity controller RS8GG602 © Danfoss 2015-03 5
External display
An external display can be tted in order for P0 (Suction) and Pc
(Condensing) readings to be displayed.
A total of 4 displays can be tted 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 tted.
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 dierent settings in one
menu will result in dierent 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” (conguration).
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 prole 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.

6 Capacity controller RS8GG602 © Danfoss 2015-03 AK-PC 781
Alarm
Error
Light-emitting diodes
A number of light-emitting diodes makes it possible to follow the
signals that are received and transmitted by the controller.
Log
From the log function you can dene the measurements you wish
to be shown.
The collected values can be printed, or you may export them to a
le. You can open the le in Excel.
If you are in a service situation you can show measurements in a
trend function. The measurements are then made real-time and
displayed instantly.
Alarm
The display gives you an overview of all active alarms. If you wish
to conrm that you have seen the alarm you can cross it o in the
acknowledge eld.
If you want to know more about a current alarm you can click on it
and obtain an information display on the screen.
A corresponding display exists for all earlier alarms. Here you can
upload information if you need further details about the alarm
history.
Trouble-shooting
The controller contains a function that continuously follows
a number of measurements and deals with them. The result
indicates whether the function is OK or whether an error may be
expected within a given period of time (“the trip down the roller
coaster has started”). At this time an alarm is transmitted about
the situation – no error has appeared as yet, but it will come.
One example may be slow clogging-up of a condenser. When the
alarm comes the capacity has been reduced, but the situation is
not serious. There will be time to plan a service call.
■Power
■Comm
■DO1 ■Status
■DO2 ■Service Tool
■DO3 ■LON
■DO4 ■I/O Extension
■DO5 ■Alarm
■DO6
■DO7
■DO8 ■Service Pin
Slow ash = OK
Quick ash = answer from gateway
Constantly ON = error
Constantly OFF = error
Flash = active alarm/not cancelled
Constant ON = Active alarm/cancelled

AK-PC 781 Capacity controller RS8GG602 © Danfoss 2015-03 7
2. Design of a controller
This section describes how the controller is designed.
The controller in the system is based on a uniform connection
platform where any deviations from regulation to regulation is
determined by the used top part with a specic software and
by which input and output signals the relevant application will
require. If it is an application with few connections, the controller
module (top part with belonging bottom part) may be sucient.
If it is an application with many connections it will be necessary to
use the controller module plus one or more extension modules.
This section will give you a survey of possible connections plus
assistance in selecting the modules required by your actual ap-
plication.

8 Capacity controller RS8GG602 © Danfoss 2015-03 AK-PC 781
Extension module with ad-
ditional analog inputs
Extension module with additional
relay outputs and additional ana-
log inputs.
The module with additional relay outputs is
also available in a version where the top part
is provided with change-over switches so
that the relays can be overridden.
Extension module with
2x analog output signals
Top part
Controller with analog inputs and
relay outputs.
External display for
suction pressure etc.
Bottom part
Module survey
• Controller module – capable of handling minor plant require-
ments.
• Extension modules. When the complexity becomes greater
and additional inputs or outputs are required, modules can be
attached to the controller. A plug on the side of the module will
transmit the supply voltage and data communication between
the modules.
• Top part
The upper part of the controller module contains the intelli-
gence. This is the unit where the regulation is dened and where
data communication is connected to other controllers in a big-
ger network.
• Connection types
There are various types of inputs and outputs. One type may, for
example, receive signals from sensors and switches, another may
receive a voltage signal, and a third type may be outputs with
relays etc. The individual types are shown in the table below.
• Optional connection
When a regulation is planned (set up) it will generate a need for
a number of connections distributed on the mentioned types.
This connection must then be made on either the controller
module or an extension module. The only thing to be observed
is that the types must not be mixed (an analog input signal must
for instance not be connected to a digital input).
• Programming of connections
The controller must know where you connect the individual
input and output signals. This takes place in a later congura-
tion where each individual connection is dened based on the
following principle:
- to which module
- at which point (”terminals”)
- what is connected (e.g. pressure transmitter/type/
pressure range)
If the row of modules needs to
be interrupted due to length or
external positioning, a communi-
cation module should be used.

AK-PC 781 Capacity controller RS8GG602 © Danfoss 2015-03 9
Type Analog
inputs
On/O outputs On/o supply voltage
(DI signal)
Analog
outputs
Stepper
output
Module with
switches
For sensors, pres-
sure transmitters
etc.
Relay
(SPDT)
Solid state Low voltage
(max. 80 V)
High voltage
(max. 260 V)
0-10 V d.c. For valves
with step
control
For override of
relay outputs
Controller 11 4 4 - - - -
Extension modules
AK-XM 101A 8
AK-XM 102A 8
AK-XM 102B 8
AK-XM 103A 4 4
AK-XM 204A 8
AK-XM 204B 8 x
AK-XM 205A 8 8
AK-XM 205B 8 8 x
AK-XM 208C 8 4
The following extension module can be placed on the PC board in the controller module.
There is only room for one module.
AK-OB 110 2
Type Function Application
Operation
AK-ST 500 Software for operation of AK controllers AK-operation
- Cable between PC and AK controller AK - Com port
-Cable between zero modem cable and AK controller /
Cable between PDA cable and AK controller AK - RS 232
- Cable between PC and AK controller AK - USB
Accessories Power supply module 230 V / 115 V to 24 V d.c.
AK-PS 075 18 VA
Supply for controllerAK-PS 150 36 VA
AK-PS 250 60 VA
Accessories External display that can be connected to the controller module. For showing, say, the suction pressure
EKA 163B Display
EKA 164B Display with operation buttons
EKA 166 Display with operation buttons and LED for function cut in
AK-MMI Graphic display with operation
-Cable between display and controller Length = 2 m, 6 m
Cable between graphic display and controller Length = 1.5 m, 3.0 m
Accessories Real time clock for use in controllers that require a clock function, but are not wired with data communication.
AK-OB 101A Real time clock with battery backup. To be mounted in an AK controller
Accessories Communication modules for controllers where modules cannot be connected continuously
AK-CM 102 Communication module Data communication for external extension
modules
Type Function Application
AK-PC 781 Controller for capacity control of compressors and condensers
8 compressors with up to 3 unloaders, 8 fans, max. 120 inputs/outputs
Compressor / Condenser / Both/
Oil management / Heat recovery / CO2 gas
pressure
1. Controller
2. Extension modules and survey of inputs and outputs
3. AK operation and accessories
On the following pages there is data specic to each module.

10 Capacity controller RS8GG602 © Danfoss 2015-03 AK-PC 781
Common data for modules
Supply voltage 24 V d.c./a.c. +/- 20%
Power consumption AK-__ (controller) 8 VA
AK-XM 101, 102, 103, 107, AK-CM 102 2 VA
AK-XM 204, 205, 208 5 VA
Analog inputs Pt 1000 ohm /0°C Resolution: 0.1°C
Accuracy: +/- 0.5°C
Pressure transmitter type AKS 32R / AKS
2050
AKS 32 (1-5 V)
Resolution:1 mV
Accuracy +/- 10 mV
Max. connection of 5 pressure transmitters on one module
Other pressure transmitter:
Ratiometric signal
Min. and Max. pressure must be set
Voltage signal 0-10 V
Contact function (On/O ) On at R < 20 ohm
O at R > 2K ohm
(Gold -plated contacts not necessary)
On/o supply voltage inputs Low voltage
0 / 80 V a.c./d.c.
O: U < 2 V
On: U > 10 V
High voltage
0 / 260 V a.c.
O: U < 24 V
On: U > 80 V
Relay outputs
SPDT
AC-1 (ohmic) 4 A
AC-15 (inductive) 3 A
UMin. 24 V
Max. 230 V
Low and high voltage must not be connected to the same
output group
Solid state outputs Can be used for loads that are cut in and
out frequently, e.g. :
Oil valves, fans and AKV valves
Max. 240 V a.c. , Min. 48 V a.c.
Max. 0,5 A,
Leak < 1 mA
Max. 1 AKV
Stepper outputs Used for valves with stepper input 20-500 step/s
Separate supply to stepper outputs : 24 a.c./d.c. / 13 VA
Ambient temperature During transport -40 to 70°C
During operation -20 to 55°C ,
0 to 95% RH (non condensing)
No shock inuences / vibrations
Enclosure Material PC / ABS
Density IP10 , VBG 4
Mounting For mounting on panel wall or DIN rail
Weight with screw terminals Modules in 100- / 200- / controller-series Ca. 200 g / 500 g / 600 g
Approvals EU low voltage directive and EMC require-
ments are complied with
LVD tested according to EN 60730
EMC tested
Immunity according to EN 61000-6-2
Emission according to EN 61000-6-3
UL 873, UL le number: E166834 for XM and CM-modules
UL le number: E31024 for PC-modules
The mentioned data applies to all modules.
If data is specic, this is mentioned together with the module in question.

AK-PC 781 Capacity controller RS8GG602 © Danfoss 2015-03 11
Dimensions
The module dimension is 72 mm.
Modules in the 100-series consist of one
module
Modules in the 200-series consist of two
modules
Controllers consist of three modules
The length of an aggregate unit = n x 72 + 8

12 Capacity controller RS8GG602 © Danfoss 2015-03 AK-PC 781
Controller
Function
There are several controllers in the series. The function is deter-
mined by the programmed software, but outwardly the control-
lers are identical – they all have the same connection possibilities:
11 analog inputs for sensors, pressure transmitters, voltage signals
and contact signals.
8 digital outputs, with 4 Solid state outputs and 4 relay outputs
Supply voltage
24 V a.c. or d.c. to be connected to the controller.
The 24 V must not be retransmitted and used by other control-
lers as it is not galvanically separated from inputs and outputs. In
other words, you must use a transformer for each controller. Class
II is required. The terminals must not be earthed.
The supply voltage to any extension modules is transmitted via
the plug on the right-hand side.
The size of the transformer is determined by the power require-
ment of the total number of modules.
The supply voltage to a pressure transmitter can be taken either
from the 5 V output or from the 12 V output depending on trans-
mitter type.
Data communication
If the controller is to be included in a system, communication
must take place via the LON connection.
The installation has to be made as mentioned in the separate
instructions for LON communication.
Address setting
When the controller is connected to a gateway type AKA 245,
the controller’s address must be set between 1 and 119. (If it is a
system manager AK-SM .., then 1-999).
Service PIN
When the controller is connected to the data communication
cable the gateway must have knowledge of the new controller.
This is obtained by pushing the key PIN. The LED“Status”will ash
when the gateway sends an acceptance message.
Operation
The conguration operation of the controller must take place
from the software program“Service Tool”. The program must be
installed on a PC, and the PC must be connected to the controller
via the network plug on the front of the unit.
Light-emitting diodes
There are two rows with LED’s. They mean:
Left row:
• Voltage supply to the controller
• Communication active with the bottom PC board (red = error)
• Status of outputs DO1 to DO8
Right row:
• Software status (slow ash = OK)
• Communication with Service Tool
• Communication on LON
• Communication with AK-CM 102
• Alarm when LED ashes
- 2 LED’s that are not used
• “Service Pin” switch has been activated A small module (option board) can be placed on the bottom part
of the controller. The module is described later in the document.
■Power
■Comm
■DO1 ■Status
■DO2 ■Service Tool
■DO3 ■LON
■DO4 ■I/O Extension
■DO5 ■Alarm
■DO6
■DO7
■DO8 ■Service Pin
PIN
Address Keep the safety
distance!
Low and high
voltage must not
be connected to
the same output
group
Slow ash = OK
Quick ash = answer from gateway
Constantly ON = error
Constantly OFF = error
Flash = active alarm/not cancelled
Constant ON = Active alarm/cancelled

AK-PC 781 Capacity controller RS8GG602 © Danfoss 2015-03 13
Point
Signal Signal
type
S
Pt 1000 ohm/0°C
S1
S2
Saux_
SsA
SdA
Shr
Stw
Sgc
Pt 1000
P
AKS 32R
AKS 32
P0A
P0B
PcA
PcB
Paux
Pgc
Prec
AKS 32R /
AKS 2050
-1 - xx bar
AKS 32
-1 - zz bar
U
...
0 - 5 V
0 - 10 V
On/O Ext.
Main
switch
Day/
Night
Door
Level
switch
Active at:
Closed
/
Open
DO
AKV
Comp 1
Comp 2
Fan 1
Alarm
Light
Rail heat
Defrost
Solenoid
valve
Active at:
On
/
O
Option Board Please see the signal
on the page with the
module.
Signal Module Point Terminal Signal type /
Active at
1
1(AI 1) 1 - 2
2(AI 2) 3 - 4
3(AI 3) 5 - 6
4(AI 4) 7 - 8
5(AI 5) 9 - 10
6(AI 6) 11 - 12
7(AI 7) 13 - 14
8(AI 8) 19 - 20
9(AI 9) 21 - 22
10 (AI 10) 23 - 24
11 (AI 11) 25 - 26
12 (DO 1) 31 - 32
13 (DO 2) 33 - 34
14 (DO 3) 35 - 36
15 (DO 4) 37 - 38
16 (DO 5) 39 - 40- 41
17 (DO6) 42 - 43 - 44
18 (DO7) 45 - 46 - 47
19 (DO8) 48 - 49 - 50
24 -
25 -
Terminal 15: 12 V
Terminal 16: 5 V
Terminal 27: 12 V
Terminal 28: 5 V
Terminal
17, 18, 29, 30:
(Cable screen)
Solid state outputs
on 12 - 15
Relay or AKV coil
fx 230 V a.c.
Relay outputs on
16 - 19
Analog
inputs
on 1 - 11
Point 1 2 3 4 5 6 7 8 9 10 11
Type AI1 AI2 AI3 AI4 AI5 AI6 AI7 AI8 AI9 AI10 AI11
Point 12 13 14 15 16 17 18 19
Type DO1 DO2 DO3 DO4 DO5 DO6 DO7 DO8
24 and 25 used
only when "Op-
tion board tted"
3: Brown
2: Blue
1: Black
3: Brown
2: Black
1: Red
AKV

14 Capacity controller RS8GG602 © Danfoss 2015-03 AK-PC 781
Extension module AK-XM 101A
Function
The module contains 8 analog inputs for sensors, pressure trans-
mitters, voltage signals and contact signals.
Supply voltage
The supply voltage to the module comes from the previous mod-
ule in the row.
Supply voltage to a pressure transmitter can be taken from either
the 5 V output or the 12 V output depending on transmitter type.
Light-emitting diodes
Only the two top LED’s are used. They indicate the following:
• Voltage supply to the module
• Communication with the controller is active (red = error)

AK-PC 781 Capacity controller RS8GG602 © Danfoss 2015-03 15
Signal Module Point Terminal Signal type /
Active at
1(AI 1) 1 - 2
2(AI 2) 3 - 4
3(AI 3) 5 - 6
4(AI 4) 7 - 8
5(AI 5) 17 - 18
6(AI 6) 19 - 20
7(AI 7) 21 - 22
8(AI 8) 23 - 24
Point
Signal Signal
type
S
Pt 1000 ohm/0°C
S1
S2
Saux
SsA
SdA
Shr
Stw
Sgc
Pt 1000
P
AKS 32R
AKS 32
P0A
P0B
PcA
PcB
Paux
Pgc
Prec
AKS 32R /
AKS 2050
-1 - xx bar
AKS 32
-1 - zz bar
U
... 0 - 5 V
0 - 10 V
On/O Ext.
Main
switch
Day/
Night
Door
Level
switch
Active at:
Closed
/
Open
Point 5 6 7 8
Type AI5 AI6 AI7 AI8
Point 1 2 3 4
Type AI1 AI2 AI3 AI4
Terminal 9: 12 V
Terminal 10: 5 V
Terminal 15: 5 V
Terminal 16: 12 V
Terminal
11, 12, 13, 14:
(Cable screen)
At the top the
signal input is
the left of the
two terminals.
At the bottom
the signal input
is the right of the
two terminals.
3: Brown
2: Blue
1: Black
3: Brown
2: Black
1: Red

16 Capacity controller RS8GG602 © Danfoss 2015-03 AK-PC 781
AK-XM 102B
Max. 230 V
On/O:
On: DI > 80 V a.c.
O: DI < 24 V a.c.
AK-XM 102A
Max. 24 V
On/O:
On: DI > 10 V a.c.
O: DI < 2 V a.c.
Extension module AK-XM 102A / AK-XM 102B
Function
The module contains 8 inputs for on/o voltage signals.
Signal
AK-XM 102A is for low voltage signals.
AK-XM 102B is for high voltage signals.
Supply voltage
The supply voltage to the module comes from the previous
module in the row.
Light-emitting diodes
They indicate:
• Voltage supply to the module
• Communication with the controller is active (red = error)
• Status of the individual inputs 1 to 8 (when lit = voltage)

AK-PC 781 Capacity controller RS8GG602 © Danfoss 2015-03 17
Signal Module Point Terminal Active at
1(DI 1) 1 - 2
2(DI 2) 3 - 4
3(DI 3) 5 - 6
4(DI 4) 7 - 8
5(DI 5) 9 - 10
6(DI 6) 11 - 12
7(DI 7) 13 - 14
8(DI 8) 15 - 16
Point
Signal Active at
DI Ext.
Main
switch
Day/
Night
Comp.
safety 1
Comp.
safety 2
Level
switch
Closed
(voltage on)
/
Open
(voltage o)
Point 5 6 7 8
Type DI5 DI6 DI7 DI8
Point 1 2 3 4
Type DI1 DI2 DI3 DI4
AK-XM 102A: Max. 24 V
AK-XM 102B: Max. 230 V

18 Capacity controller RS8GG602 © Danfoss 2015-03 AK-PC 781
Extension module AK-XM 103A
Function
The module contains :
4 analog inputs for sensors, pressure transmitters, voltage signals
and contact signals.
4 analog voltage outputs of 0 - 10 V
Supply voltage
The supply voltage to the module comes from the previous
module in the row.
Supply voltage to a pressure transmitter can be taken from either
the 5 V output or the 12 V output depending on transmitter type.
Galvanic isolation
The inputs are galvanically separated from the outlets.
The outlets AO1 and AO2 are galvanically separated from AO3 and
AO4.
Light-emitting diodes
Only the two top LED’s are used. They indicate the following:
• Voltage supply to the module
• Communication with the controller is active (red = error)

AK-PC 781 Capacity controller RS8GG602 © Danfoss 2015-03 19
Signal Module Point Terminal Signal type /Active at
1(AI 1) 1 - 2
2(AI 2) 3 - 4
3(AI 3) 5 - 6
4(AI 4) 7 - 8
5(AO 1) 17 - 18
6(AO 2) 19 - 20
7(AO 3) 21 - 22
8(AO 4) 23 - 24
Point
Signal Signal
type
S
Pt 1000 ohm/0°C
S1
S2
Saux
SsA
SdA
Shr
Stw
Sgc
Pt 1000
P
AKS 32R
AKS 32
P0A
P0B
PcA
PcB
Paux
Pgc
Prec
AKS 32R /
AKS 2050
-1 - xx bar
AKS 32
-1 - zz bar
U
... 0 - 5 V
0 - 10 V
On/O Ext.
Main
switch
Day/
Night
Door
Level
switch
Active at:
Closed
/
Open
AO
0-10 V
Terminal 9: 12 V
Terminal 10: 5 V
Terminal
11, 12:
(Cable screen)
Galvanic isolation:
AI 1-4 ≠ AO 1-2 ≠ AO 3-4
Point 5 6 7 8
Type AO1 AO2 AO3 AO4
Point 1 2 3 4
Type AI1 AI2 AI3 AI4
3: Brown
2: Blue
1: Black
3: Brown
2: Black
1: Red
At the top the
signal input is
the left of the
two terminals.
At the bottom
the signal input
is the right of the
two terminals.

20 Capacity controller RS8GG602 © Danfoss 2015-03 AK-PC 781
Extension module AK-XM 204A / AK-XM 204B
AK-XM 204A AK-XM 204B
Max. 230 V
AC-1: max. 4 A (ohmic)
AC-15: max. 3 A (Inductive)
Function
The module contains 8 relay outputs.
Supply voltage
The supply voltage to the module comes from the previous mod-
ule in the row.
AK-XM 204B only
Override of relay
Eight change-over switches at the front make it possible to over-
ride the relay’s function.
Either to position OFF or ON.
In position Auto the controller carries out the control.
Light-emitting diodes
There are two rows with LED’s. They mean:
Left row:
• Voltage supply to the controller
• Communication active with the bottom PC board (red = error)
• Status of outputs DO1 to DO8
Right row: (AK-XM 204B only):
• Override of relays
ON = override
OFF = no override
Fuses
Behind the upper part there is a fuse for each output.
Keep the safety distance!
Low and high voltage
must not be connected to
the same output group
AK-XM 204B
Override of relay
Note
If the changeovers are used to override the compressor operation,
it is necessary to wire a safety relay into the circuit for oil manage-
ment. Without this safety relay, the controller will fail to stop the
compressor if it should run out of oil. See Regulating functions.