Danfoss AK-PC 551 Design guide

AK-PC 551 Refrigeration Controller

Technical brochure

2 Technical brochure RC8CF102 © Danfoss 08-2014 AK-PC 551

Content

Introduction �� 4

Applications 4 Compressor combinations 5 Condenser combinations 5 Inputs and outputs 5

Basic Operation �� 6

Status 6 Password 6 Logout 6 Setup & service 6 View parameters 8 Change parameters 8 Day / night schedule 8

First time start up �� 9

Conguration 9

Example: Application �� 10

Application: Digital scroll 10

Example: Wiring Diagram �� 11

Electrical wiring 11 Connection, lower level 11 Electrical diagram 11 Connection, upper level 11

Example: Wizard �� 12

Wizard setup 12

Example: Check IO conguration �� 14

Wizard assignment of inputs and outputs (I/0) 14 Assignment of inputs and outputs 14 IO conguration error 15

Example: Add extra I/O �� 16

Example: Check I/O wiring �� 17

Initialize the controllers IO conguration 17

Network setup �� 18

Example: Quick conguration �� 19

Quick conguration 19 Application table 20

Frequently asked questions (FAQ) �� 22

AK-PC 551 Technical brochure RC8CF102 © Danfoss 08-2014 3

Introduction

This technical brochure will give you a short introduction to the AK-PC 551 pack controller� With an application example, it is shown how easy the controller is congured and operated through the graphical display�

The AK-PC 551 is a pack controller for 1 or 2 suction groups of compressors and a common condenser�

AK-PC 551 supports a variety of compressor combinations including variable speed, Digital scroll and Stream 4 cylinder compressors� Additionally it oers a large number of energy saving functions and optimization features�

AK-PC 551 can be fully congured through a LCD display� The LCD display can be built in and/or be a remote connected display�

AK-PC 551 has a compact size of 8 DIN modules� All inputs and outputs can be congured for a variety of functions making the controller highly adaptable to any pack application�

AK-PC 551 can be connected into a MODBUS communication network and is available with 24 Vac or 110-230 Vac power supply�

Applications

AK-PC 551 is used for capacity control of compressors and condenser fans on small to medium sized refrigeration systems� It covers the following main applications:

• One compressor group (max� 8 relays) and one condenser group

• Two compressor groups (max� 4 relays per group) and a common condenser

4 Technical brochure RC8CF102 © Danfoss 08-2014 AK-PC 551

Introduction

Compressor combinations

The compressor capacity can be controlled according to the suction pressure Po or a media temperature sensor S4� AK-PC 551 covers a variety of compressor combinations�

Condenser combinations

The condenser capacity can be controlled according to the condensing pressure Pc or a media temperature sensor S7 The condenser can be controlled in two ways:

• Speed control of all fans

• Step control of single fans

Inputs and outputs

All in- and outputs of an AK-PC 551 controller can be congured for various functions and signal types:

• 8 analogue inputs for pressure transmitters and temperature sensors�

• 6 digital relay outputs for compressors, fans, alarm�

• 2 digital solid state outputs for PWM control of Digital scroll or Stream compressor� If not used for this purpose they can be used as normal relay outputs�

• 2 analogue outputs for speed control of compressors and condenser fans�

Speed control of all fans Step control of all fans

AK-PC 551 Technical brochure RC8CF102 © Danfoss 08-2014 5

Basic Operation

Conguration and daily operation of AK-PC 551 is done via the built-in display or via a remote connected display� The display supports multiple languages and engineering units�

For a full description of the controller parameters please see the manual RS8GY

Status

Get an overview of how the system is running in the status screens� Use the LEFT / RIGHT buttons to view the status screens�

Suction statusHome Condenser status Active alarms Cleared alarms Controller information

Password

Parameters and menus are protected by a password that gives access on 3 dierent user levels�

Level 0: See parameters (000) Level 1: Change weekly schedule (100) Level 2: Change control setpoints (200) Level 3: Change conguration setpoints (300)

The password cannot be reset, so please remember the (level 3) password�

Logout

Go to the "Home" screen and hold down the X key for 5 seconds to logout�

Setup & service

In the main menu you will nd all control parameters divided into sub menus�

From any status screen press ENTER for 2 sec� to access main menu

Press ESCAPE to go back to status Press UP to decrease digit Press DOWN to increase digit

Press LEFT / RIGHT to go to next / previous digit

Press ENTER to login

Press ESCAPE to go one level back

6 Technical brochure RC8CF102 © Danfoss 08-2014 AK-PC 551

Basic Operation

The number of status screens and the presented data depends upon the congured application�

Home

Number of compressors running

(1 of 2 compressors is running)

Suction control sensor readout

Suction reference

Condenser reference

Condenser control sensor readout

Number of fans running

(1 of 2 fans is running)

Suction status

Running compressor capacity

Condenser control sensor

Condenser status

Condenser control sensor

Condenser reference Suction control sensor

Suction reference

Active alarms

Active alarm

Press ENTER to see alarm details

Alarm text Alarm priority Alarm activated at

To clear an alarm press ESC (X) for 2 sec�

Running fan capacity

Condenser reference

Cleared alarms

? temperature

Cleared alarm

Press ENTER to see cleared alarm details

Alarm text

Alarm priority

Alarm activated at

Alarm cleared at

Controller information

Technical controller information like code number and software version etc�

AK-PC 551 Technical brochure RC8CF102 © Danfoss 08-2014 7

Basic Operation

View parameters

The display will only present parameters that are valid for the congured application e�g� if 4 compressors are selected only 4 are showed�

A partly highlighted row indicates that a parameter can be viewed and not changed�

Press ENTER

Control status menu

Change parameters

A full highlighted row indicates that a parameter can be changed� A changable parameter has a frame around the setting�

to select control status

Control status readout

Press ESCAPE to go back one level

Press DOWN to see next parameter

Control settings menu

Day / night schedule

System menu

to select setpoint

Press ENTER to select weekly schedule

Setpoint readout

Setpoint selected

Weekly schedule

Monday open time

Press ESCAPE to go one level back

Press DOWN to see next parameter Press ENTER to edit a parameterPress ENTER

Press ESCAPE to go one level back Press UP to increace the setpoint Press DOWN to decrease the setpoint Press ENTER to save the setpoint

Press ENTER to select day

Press ESCAPE to go one level back Press UP to increace the time Press DOWN to decrease the time

Press LEFT / RIGHT to go to hour / minute

Press ENTER to save the setting

8 Technical brochure RC8CF102 © Danfoss 08-2014 AK-PC 551

First time start up

Conguration

After installation the controller must be congured for an application� Once power is applied to the controller, the "Power on" screen will appear�

Use one of the three options to congure the controller:

• Setup wizard

• Quick configuration

• Parametric setup

Setup wizard

Setup wizard is a step by step up and running guideline, setting

up inputs and outputs automatically�

Quick conguration

Quick conguration is a series of precongured applications,

setting up inputs and outputs automatically�

Parametric setup

Parametric setup is for the expert user, who wants to set each parameter individually, adjust or netune settings�

Power on screen

Quick start

Press ENTER for 2 sec� and enter password (300) to access quick start

AK-PC 551 Technical brochure RC8CF102 © Danfoss 08-2014 9

Example: Application

Application: Digital scroll

The conguration and daily operation of the AK-PC 551 will be explained via an application example:

AK-PC 551 controls a refrigeration system with two suction groups of compressors and a common air cooled condenser�

Refrigerant: R404A

Suction group MT: 1 digital scroll compressor 2 single step scroll compressors Control according to suction pressure Po Set point -15 °C Monitoring of discharge temperature of digital scroll

Suction group LT: 2 single step scroll compressors Control according to suction pressure Po Set point -30°C

Condenser: Speed control of 4 fans Common safety monitoring of fans Relay output for start/stop of VSD Control according to condensing pressure Pc Floating reference according to Sc3 outdoor temp�

10 Technical brochure RC8CF102 © Danfoss 08-2014 AK-PC 551

Example: Wiring Diagram

Electrical wiring

The electrical wiring is laid out according to the wizard rules for assigning functions to the inputs and outputs

DO Function DI Function AO Function AI Function

DO1 Com� 1A DI1 Comp� 1A safety AO3 Fan VSD AI1 PoA suction pressure

DO2 Comp� 2A DI2 Comp� 2A safety AO4 AI2 PoB suction pressure

DO3 Comp� 3A DI3 Comp� 3A safety AI3 Pc condensing pressure

DO4 Comp� 1B DI4 Comp� 1B safety AI4 Sc3 outdoor temp�

DO5 Comp� 1A PWM DI5 Comp� 2B safety AI5 Sd Comp� 1A

DO6 Comp� 2B DI6 Fan safety AI6

DO7 Fan VSD DI7 AI7

DO8 DI8 AI8

Connection, lower level

Electrical diagram

Connection, upper level

AK-PC 551 Technical brochure RC8CF102 © Danfoss 08-2014 11

Example: Wizard

Wizard setup

In this example we will use the wizard to congure the controller�

Press ENTER for 2 sec� and enter password (300) to access quick start

Press ENTER to select the wizard

General

In the rst general screens you must select how data are presented in the display� Please note that the “Control setup unit” decides whether the control set points are presented in pressure units or temperature units (saturated temperature)�

Press ESCAPE to leave the wizard

Press ENTER to start the wizard

Wizard screens: Settings:

Language: English Control setup unit: Sat. temp Temperature units: °C Pressure units: Bar

Plant type

Select the overall application of the controller and the refrigerant type�

Suction A and B

Set the compressor combination as well as the compressor sizes, control sensor and set point� The pressure range of the pressure transmitter can be set�

Select plant type: 2 comp + 1 cond Refrigerant type: R404A

Suction A Po sensor max� range: 12.0 bar Po sensor min� range: -1.0 bar Setpoint: -15 °C Compressor mode: Digital scroll No� of compressors: 3 Lead compressor size: 5 kW Comp� size: 5 kW

Suction B Po sensor max� range: 12 bar Po sensor min� range: -1.0 bar Setpoint: -30 °C Compressor mode: Single step No� of compressors: 2 Comp� size: 3 kW

12 Technical brochure RC8CF102 © Danfoss 08-2014 AK-PC 551

Example: Wizard

Condenser

Set the condenser control as well as control sensor and reference settings� The pressure range of the pressure transmitter can be set�

Extra

Select whether to use an alarm relay and Modbus network address�

Pc sensor max� range: 34.0 bar Pc sensor min� range: -1.0 bar Reference mode: Floating Setpoint: 30 °C Min� reference: 15 °C Max� reference: 45 °C Capacity ctrl� mode: Speed No� of fans: 1 VSD Start via DO: Yes Monitor fan safety: Common

Alarm output: No relay Modbus address: 100

Summary

Get an overview of the inputs and outputs generated by the wizard�

Apply wizard settings

Press ENTER to apply the wizard settings to the controller including automatic assignment requested inputs and outputs�

Next step

Select which main menu to go to� Press DOWN to go to the selected menu�

It is recommended to check the IO (input / output) conguration before starting the controller�

Press DOWN to go to the selected menu and nish the wizard

AK-PC 551 Technical brochure RC8CF102 © Danfoss 08-2014 13

Example: Check IO conguration

Wizard assignment of inputs and outputs (I/0)

Once the wizard is applied, the IO functions are automatically assigned to hardware inputs and outputs�

The screens below shows how the IO functions are assigned according to the example�

Press ENTER to select

Main menu IO conguration menu

Digital outputs Digital inputs Analog outputs Analog inputs

I/O conguration

Press ENTER to select digital and analog I/O

Assignment of inputs and outputs

The table indicates rules for assignment of inputs and outputs via the wizard�

Digital outputs (DO1-DO8) Digital inputs (DI1-DI8) Analog outputs (AO3 – AO4) Analog inputs(AI1-AI8)

PWM outputs for capacity control of Digital scroll or Stream 4 compressor are placed on the solid state relays DO5 and DO6

Starting from DO1: Fan safety inputs Speed control of condenser Pc condensing pressure is

Compressor start relays followed by unloading valves for respectively suction group A and B

Condenser fan HP safety switch* S4A and S4B suction media

Injection ON for A/B * LP safety switch * S7 condenser media

Alarm relay Night setback * Sd komp� 1 discharge temp�

Compressor safety inputs for respectively suction group A and B

External Main switch (ON/ OFF) *

Heat recovery * Ss suction gas temperature for

Load shedding * Sd discharge temperature for

General alarm inputs 1-3 * Saux for general thermostat *

Speed control of compressor for respectively suction group A and B

PoA og PoB suctionpressure are placed on AI1 and AI2

placed on AI3

Sc3 outdoor temperature is placed on AI4

temperature sensors *

temperature sensor *

sensor for digital scroll/Stream compressor for suction A and B

suction group A and B *

suction A and B *

* Special features to be enabled through conguration screens. Not part of the wizard setup.

14 Technical brochure RC8CF102 © Danfoss 08-2014 AK-PC 551

Example: Check IO conguration

IO conguration error

If you get an “IO conguration error” alarm after setting main switch in ON position, the reasons can be:

• Not all enabled IO functions have been assigned to a hardware input or output

• The number of enabled IO functions exceeds the number of available inputs or outputs of the controller

IO summary

Go to Main menu -> IO Status -> IO summary

If the number of enabled IO functions exceeds the maximum number supported by the hardware, an exclamation mark “!” will be shown at the IO type in question� This means that you will have to disable some of the IO functions via the conguration menus of the suction groups and condenser in order not to exceed the maximum available inputs or outputs�

If no exclamation mark is shown it means that at least one IO function has not been assigned to a hardware input or output� This means that you will have to go into the IO conguration menu of each IO type, select a free input/output and select the missing function (if a function is selectable this is the reason for the IO conguration error alarm)�

Alarm: IO conguration error

I/O summary

An exclamation mark is shown when max. number of IO is exceeded !

AK-PC 551 Technical brochure RC8CF102 © Danfoss 08-2014 15

Example: Add extra I/O

Add extra I/O

The wizard covers all basic functions of the AK-PC 551 pack controller� Additional features can be set through the conguration screens of the suction group or the condenser�

In this example we will add a Sd discharge temperature monitoring of both suction groups�

1. Enable Sd temperature monitoring in suction group A and B

Go to Main menu -> Suction A ->Conguration

2. Assign the two Sd discharge temperature sensors to free analog inputs

Go to Main menu -> IO conguration of analog inputs (AI)

Conguration menu

Sd discharge temp.

3. Select the Sd A and Sd B discharge sensors for respectively AI6 and AI7

Please notice that it is only functions that are enabled in the suction/condenser conguration menus that are selectable in the IO conguration�

PWM outputs for Digital scroll or Stream compressors can only be selected on the solid state relays DO5 and DO6�

Pressure transmitters with current signals of 0-20mA or 4-20mA are only supported on AI1-AI4�

If a function has been assigned to an input or output and the same function has been deselected in the suction/condenser conguration afterwards, the IO conguration will show an exclamation mark at the function� This is done in order to show that an IO point is occupied by a function which is not used by the controller�

Analog inputs menu

Analog input (AI) no. 6

AI no. 6 function

Analog inputs

An exclamation mark is shown when an IO point is occupied by a function which is not used by the controller.

In this situation you should either enable the function again in the suction/condenser conguration menus or deselect the function in the IO conguration�

16 Technical brochure RC8CF102 © Danfoss 08-2014 AK-PC 551

Example: Check I/O wiring

Initialize the controllers IO conguration

1. Set main switch in ON position

Go to Main menu -> Start/Stop

Set main switch ON

2. Check correct reading of inputs and outputs in the IO status menus

Go to Main menu -> IO Conguration -> Analog/Digital inputs

Check correct status of all inputs�

3. Check correct wiring of the outputs via the IO manual control menus

Go to Main menu -> IO Conguration -> Analog/Digital outputs

Check correct electrical wiring by manually overriding the outputs�

Main switch menu

Analog inputs Digital inputs

The stars "****" indicates that sensor error is detected or not intialized (main switch ON).

Digital outputs

Digital output 1 ON

AK-PC 551 Technical brochure RC8CF102 © Danfoss 08-2014 17

Network setup

AK-PC 551 can be integrated into a Modbus communication network� It is important that the installation of the communication cable is done correctly� Also remember correct termination at both ends of the cable� Please refer to separate literature no� RC8AC

When AK-PC 551 is integrated into an ADAP-KOOL® network with a system manager of the types AK-SC 355 or AK-SM 850 it is important that some settings are set correctly�

1. Set unit of setpoints

Go to Main menu -> Plant type

The "Unit of setpoints" has to be set up before the controller is scanned on the network� This is required in order for the front end (AK-SC 355 or AK-SM 850) to present settings/readings in the correct units (saturated temperature or pressure)�

2. Set network address

Go to Main menu -> System -> Network

3. Set the Modbus address in the range 1-199

- assuring that the selected address is not occupied by another controller on the network�

Unit of setpoints

Network

4. Make sure that the Baud rate of the controller is set to “384”

(38400 bits per second)

5. Make sure that the serial mode is set “8E1”

When a network scan is carried out the controller will be identied as:

• "AK-PC 551 - xxxx (MC250000)" - if the control setup unit is saturated temperature�

• "AK-PC 551 - xxxx (MC250001)" - if the control setup unit is pressure�

You can check the scanned controller in the front end in the menu entry: Conguration -> Network Nodes -> Scan Status

The AK-SM 850/AK-SC 355 must have software version G03�090 or higher in order to support AK-PC 551� The software version can be found in menu entry: Info -> Information -> SW version

Modbus address and Baudrate

Scanned controllers shown in the front end

18 Technical brochure RC8CF102 © Danfoss 08-2014 AK-PC 551

Example: Quick conguration

Quick conguration

As an alternative to the wizard, the controller can be set up by selecting one of the precongurations dened in the controller� Please refer to the application table (on page 18) for a full description of all selectable precongurations and the associated input and output wiring�

A quick conguration is done in ve steps:

1� Select a quick setting 2� Set language 3� Set unit of setpoints 4� Set refrigerant type 5� Set main switch on

1. Select quick setting

Go to Main menu -> Quick setup or select Quick settings at start up�

In this example is used the preconguration number 17: 3CDA + 2CB+FS

Press ENTER to select

Quick Start menu

The Quick setup can (after rst time setup) be accessed from the main menu.

2. Set language

Go to Main menu -> System -> Display

the quick settings

Quick setting

No plant type selected

After pressing ENTER the selection goes back to "None" and the selected preconguration is loaded into the controller.

Plant type selected

Default is "English"

Language

3. Set unit of setpoints

Go to Main menu -> Plant type

Unit of setpoints

AK-PC 551 Technical brochure RC8CF102 © Danfoss 08-2014 19

Default is "Sat. Temp."

Example: Quick conguration

4. Set refrigerant type

Go to Main menu -> Plant type

By default the Quick conguration will assign AKS32R type pressure transmitters for the suction and condensing pressure with -1 to 12 bar and -1 to 34 bar pressure ranges�

It is recommended to check the IO (input / output) conguration before starting the controller�

5. Set main switch ON

Go to Main menu -> Start/Stop -> Main switch

Default is "None"

Refrigerant menu

Refrigerant type R404A

Start/Stop menu

Main switch on

Application table

The application table shows the selectable precongurations number, type of compressors and condensor fans� For more details see the quick conguration table�

App. no. Display views Suction group A Suction group B Condenser

Speed Digital

(Scroll / steam)

17 3CDA + 2CB + FS 1 2 2 x

16 2CDA + 2CB + 3F 1 1 2 3

15 3CSA + 2CB + FS 1 2 2 x

14 2CSA + 2CB + 3F 1 1 2 3

13 4CA + 3CB + FS 4 3 x

12 3CA + 2CB + FS 3 2 x

11 2CA + 2CB + 3F 2 2 3

10 4CDA + FS 1 3 x

9 3CDA + FS 1 2 x

8 3CDA + 3F 1 2 3

7 2CDA + 2F 1 1 2

6 4CSA + FS 1 3 x

5 4CA + FS 4 x

4 4CA + 4F 4 4

3 3CSA + FS 1 2 x

2 3CA + FS 3 x

1 3CA + 3 F 3 3

0 None After selection the setting returns to "None"

1-step 1-step Step Speed

20 Technical brochure RC8CF102 © Danfoss 08-2014 AK-PC 551

Quick conguration table

Fan

safe�

Fan

safe�

Fan

safe�

Fan

safe�

Fan

Sw�

C1A C2A C3A C1B C2B Main

C1A C2A C1B C2B Main

Digi

safe�

Fan

safe�

Fan

safe�

Fan

safe�

Fan

safe�

Fan

safe�

Fan

safe�

Fan

safe�

Fan

safe�

Fan

safe�

Fan

safe�

Fan

safe�

Sw�

C1 C2 C3 C4 Main

C1 C2 C3 Main

C1 C2 Main

Digi

On/O Analog Analog Digital

DO1 DO2 DO3 DO4 DO5 DO6 DO7 DO8 AO3 AO4 AI1 AI2 AI3 AI4 AI5 AI6 AI7 AI8 DI1 DI2 DI3 DI4 DI5 DI6 DI7 DI8

PoA PoB Pc Sc3 SdA

Alarm Fan

C2B Fan

Speed

VSD

Fan1 Fan2 Fan3 PoA PoB Pc Sc3 SdA

PWM

PoA PoB Pc Sc3 C1A C2A C3A C1B C2B Main

Fan

Alarm C1A

PoA PoB Pc Sc3 C1A C2A C1B C2B Main

Speed

VSD

PoA PoB Pc Sc3 C1A C2A C3A C4A C1B C2B C3B Fan

Speed

PoA PoB Pc Sc3 C1A C2A C3A C1B C2B Main

Speed

Alarm Fan

Speed

VSD

PoA Pc Sc3 SdA

Alarm Fan

Fan

PoA Pc Sc3 SdA

Speed

Alarm Fan

VSD

Fan

PWM

Speed

VSD

Fan2 Fan3 Alarm PoA Pc Sc3 SdA

PWM

Alarm PoA Pc Sc3 SdA

PWM

PoA Pc Sc3 C1 C2 C3 C4 Main

Fan

Alarm C1

PoA Pc Sc3 C1 C2 C3 C4 Main

Speed

Alarm Fan

VSD

Speed

VSD

PoA Pc Sc3 C1 C2 C3 Main

Fan

Alarm C1

PoA Pc Sc3 C1 C2 C3 Main

Speed

Alarm Fan

VSD

Speed

VSD

App. no. Display views Outputs Inputs

17 3CDA + 2CB + FS C1A C2A C3A C1B C1A

16 2CDA + 2CB + 3F C1A C2A C1B C2B C1A

15 3CSA + 2CB + FS C1A C2A C3A C1B C2B Fan

14 2CSA + 2CB + 3F C1A C2A C1B C2B Fan1 Fan2 Fan3 Alarm C1A

13 4CA + 3CB + FS C1A C2A C3A C4A C1B C2B C3B Alarm Fan

12 3CA + 2CB + FS C1A C2A C3A C1B C2B Fan

11 2CA + 2CB + 3F C1A C2A C1B C2B Fan1 Fan2 Fan3 Alarm PoA PoB Pc Sc3 C1A C2A C1B CB2 Main

10 4CDA + FS C1 C2 C3 C4 C1

9 3CDA + FS C1 C2 C3 C1

8 3CDA + 3F C1 C2 C3 Fan1 C1

7 2CDA + 2F C1 C2 Fan1 Fan2 C1

6 4CSA + FS C1 C2 C3 C4 Fan

5 4CA + FS C1 C2 C3 C4 Fan

4 4CA + 4F C1 C2 C3 C4 Fan1 Fan2 Fan3 Fan4 PoA Pc Sc3 C1 C2 C3 C4 Main

3 3CSA + FS C1 C2 C3 Fan

2 3CA + FS C1 C2 C3 Fan

1 3CA + 3 F C1 C2 C3 Fan1 Fan2 Fan3 Alarm PoA Pc Sc3 C1 C2 C3 Main

0 None

Frequently asked questions (FAQ)

Question Solution

How to connect variable speed drive (VSD)?

The analogue outputs AO3 and AO4 of the AK-PC 551 pack controller is galvanic separated from the other inputs and outputs of the controller� So if the AK-PC 551 controller is ordered for 24Vac supply voltage, you can use the same 24Vac transformer for power supply of the controller and for supply of the analogue outputs�

It is recommended to use a double isolated transformer (Class II) as this type does not need to be connected to protective earth on the secondary side� This will prevent any ground loops between the AK-PC 551 pack controller and the variable speed drive connected to AO3 or AO4�

Example: Variable speed drive connected to AO3

How to connect the PWM valve of a digital scroll compressor?

The Pulse Width Modulated valve (PWM) of a digital scroll compressor must be connected to one of the solid state relays (SSR) of AK-PC 551 - which are the outputs DO5 or DO6� The PWM valve function cannot be selected for any of the other digital outputs�

The PWM valve of the digital scroll compressor works in such a way that when voltage is supplied to the valve, the digital scroll compressor is unloaded and when no voltage is supplied to the valve, the digital scroll compressor is loaded�

When the PWM valve signal is selected for DO5 or DO6, the polarity of the output signal is by default inverted and thereby the PWM valve of the digital scroll compressor can be connected directly to the AK-PC 551 without any intermediate relays�

Example: Wiring of PWM valve of digital scroll compressor to DO5/DO6 of AK-PC 551

Question Solution

How to start and stop an AK-PC 551 pack controller?

The AK-PC 551 controller has two options for start/stop of control�

Parameter set via the display: The parameter “Main switch” is used to start/stop control (see screen dumps)

Optional start/stop via digital input signal: The AK-PC 551 controller can also be controlled via a digital input signal� This function is enabled in the Plant type menu and then set up in the IO conguration of digital inputs�

If any of the two “Main switch” signals is in OFF position, the AK-PC 551 will stop all control, set all outputs in standby position and clear all active alarms�

At the same time the controller will generate a special alarm “Standby mode alarm” in order to indicate that the controller has been stopped�

How to setup and connect a pressure transmitter with 0-20 mA or 4-20 mA current signals?

How does the wizard assign functions to inputs and outputs?

Pressure transmitters with current output signals of 0-20 mA or 4-20 mA MUST be connected to one of the analogue input terminals AI1, AI2, AI3 or AI4�

The signal type and signal range of the pressure transmitter is setup in the “IO conguration” menu for analogue inputs�

In the example the suction pressure signal for suction group A, has been selected for analogue input 1 and the signal type is selected as “4-20mA”� Please be aware that the minimum and maximum pressure ranges are set in relative pressure�

The power supply for pressure transmitters with current signal must be connected to the 12 Vdc terminal of AK-PC 551� The signal wire must be connected to the analogue input pin in question�

If the AK-PC 551 controller is congured via the wizard, the required functions are automatically assigned to inputs and outputs�

At the end of the Setup wizard, the user is asked whether the controller should apply the settings made in the wizard� Please be aware that the wizard will overwrite all previous congurations, if the user selects to apply the wizard settings�

Once the user selects to apply the wizard settings, the required functions are assigned to inputs and outputs based on simple priority rules� The rules can be seen in detail in the paragraph “Example: Check IO conguration”

Question Solution

How to connect a remote display?

The remote MMIGRS2 display is connected to the controller via a cable that can be ordered with dierent lengths�

When connecting the remote display, please remember to make a short circuit of the two rightmost terminals on the terminal block to the left of the cable connection – please refer to drawing�

When are alarms cleared?

Normally alarms are automatically cleared as soon as the alarm condition is cleared�

However, some safety alarms require that a safety restart delay has to expire before the alarm condition is cleared and normal control is resumed� This goes for the following safety alarms:

• High condensing pressure

• Low suction pressure

• High discharge temperature

Furthermore sensor alarms have a clearance delay of 10 minutes (default), which means that the sensor has to be OK for 10 minutes before the alarm is cleared� However normal control procedure will be resumed as soon as the sensor signal is OK� The reason for the delay is to avoid numerous alarms if a sensor has a bad electrical connection�

Alarms can also be cleared manually by entering the alarm detail picture and pressing the “X” button for 3 seconds� If the alarm condition of a manually cleared alarm is still active the alarm will be raised again�

Press the X (escape) button for 3 seconds to clear alarms manually

Danfoss can accept no responsibility for possible errors in catalogues, brochures and other printed material� Danfoss reserves the right to alter its products without notice� This also applies to products already on order provided that such alternations can be made without subsequential changes being necessary in specications already agreed� All trademarks in this material are property of the respecitve companies� Danfoss and Danfoss logotype are trademarks of Danfoss A/S� All rights reserved�

ADAP-KOOL®

Danfoss AK-PC 551 Design guide

Specifications and Main Features

Frequently Asked Questions

User Manual