Danfoss Compressor pack controllers type AKC 25H5Vers. 1.3x Installation guide

Brand: Danfoss

Model: Compressor pack controllers type AKC 25H5Vers. 1.3x

Type: Installation guide

RC.1J.51.02 ® RC.1J.53.02 06-2000

Compressor Pack Controller

AKC 25H5

ADAP-KOOL

Function description

2 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5

Contents

Introduction ................................................................................................................................ 3

System information ................................................................................................................... 4

Operation .................................................................................................................................... 4

Language .................................................................................................................................... 4

Capacity regulation of compressor ......................................................................................... 5

Regulation ........................................................................................................................ 5

Regulation reference ........................................................................................................ 5

Neutral zone and regulating band .................................................................................... 9

Compressor definition ...................................................................................................... 9

Time delays for cut ins and cut outs .............................................................................. 10

Sequence for cut in and cut out of capacity .................................................................. 10

Signal from the compressor's safety controls ................................................................ 12

Temperature sensor ....................................................................................................... 13

Compressor control, but no condenser control ............................................................. 13

Peak load limitation ........................................................................................................ 13

Liquid injection into the suction line ................................................................................ 14

Capacity regulation of condenser ......................................................................................... 15

Regulation ......................................................................................................................15

Regulation reference ...................................................................................................... 15

Neutral zone and regulating band .................................................................................. 18

Condenser definition ...................................................................................................... 18

Time delays for cutins and cutouts ................................................................................ 18

Signal from the condenser's safety controls .................................................................. 19

Hourmeter ...................................................................................................................... 19

Condenser control, but no compressor control ............................................................. 19

Speed regulation ...................................................................................................................... 20

Valve function .......................................................................................................................... 22

Liquid injection into the suction line ................................................................................ 22

Heat recovery function ................................................................................................... 22

Overriding ................................................................................................................................. 23

Monitoring ................................................................................................................................ 24

Monitoring of maximum discharge gas temperature ..................................................... 24

Monitoring of maximum discharge pressure .................................................................. 24

Monitoring of minimum suction pressure ....................................................................... 25

Monitoring of suction gas superheat .............................................................................. 25

Monitoring of the different parts of the compressor's safety circuit ............................... 26

Monitoring of other automatic controls .......................................................................... 26

Supply voltage ......................................................................................................................... 28

Function switch ....................................................................................................................... 28

Clock function .......................................................................................................................... 28

Refrigerant ................................................................................................................................ 29

Service ...................................................................................................................................... 30

System measurements/data ................................................................................................... 32

Alarms and messages .............................................................................................................34

Access codes ........................................................................................................................... 38

Supporting text ........................................................................................................................ 38

Installation considerations ....................................................................................................38

List of literature ....................................................................................................................... 39

This function description was revised in May 2000 and applies to AKC 25H5 with code

numbers 084B2020 and 084B2021.

Validity

AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 3

Introduction AKC 25H5 is a complete control unit for capacity regulation of compressors and condensers

in commercial refrigeration.

The controller can be used in combination with other controllers in the Danfoss ADAP-KOOL

refrigeration control system.

In addition to capacity regulation the controller can transmit signals to other controllers about

operating conditions, e.g. forced closing of expansion valves, alarm signals and alarm

messages.

The controller’s main function is to control the compressors and condensers, so that they will

constantly operate at the optimum pressure conditions from an energy point of view. Both

suction pressure and condensing pressure will be controlled by signals from pressure

transmitters type AKS 32.

Among the various functions can briefly be mentioned:

- It can control a total of nine capacity steps distributed on compressor steps and condenser

steps, as required. One of the nine steps can be used for infinitely variable speed

regulation.

- There are nine digital imputs for monitoring the various automatic controls. The inputs can

be defined to monitor compressors, condensers or other ON/OFF signals, at your option. If

failure of a compressor is registered, the controller will control the capacity with the

remaining compressors.

- When the compressors stop, signals may be transmitted to the electronic expansion valves,

so that they close.

- LED’s on the front plate show the status of outputs and inputs.

- Alarm signals can be generated directly from the controller and via DANBUSS Data

Communication.

- Alarms are displayed with texts, so that it is easy to see the cause of the alarm.

The monitoring of a compressor’s safety

circuit may be extended from being a simple

type of monitoring to a more differentiated

monitoring of several parts of the safety

circuit. To achieve this, the controller must

be linked up with an alarm module type AKC

22H. This alarm module will then receive

signals from the different parts of the safety

circuit and will subsequently give an exact

report on the exact location of the problems

in the circuit.

4 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5

Controller type AKC 25H5 is a unit in the ADAP-KOOL

refrigeration control system. The

controller can be linked up with other controllers in the system via a two-core connection - the

DANBUSS Data Communication. Through this connection information can be transmitted

between the units, like settings, measurements, alarms etc.

Remote service

The different messages and alarms can, via the telephone network, be transmitted by modems

to, say, a service company.

Address coding

An address code must be set by means of a number of switches on the controller’s front plate.

There are seven switches for the coding. How coding is performed is explained in the

installation instructions for the data communication cable (literature No. RC.0X.A).

Connection of control panel type AKA 21

A plug for the connection of control panel AKA 21 is mounted right on the front plate of AKC

25H5. (If the control panel is to be used in any other place, a terminal box will have to be

installed (cf. the installation instructions for the data communication cable, literature No.

RC.0X.A).)

Data communication

To obtain correct data communication it is important that the installation instructions for the

data communication cable be adhered to (literature No. RC.0X.A).

The controller can be operated in two different ways. Either by using control panel type AKA

21 or by means of a PC with system software type AKM.

AKA 21 operation

Setting of the different functions is performed via a menu system. The menu system is built up

on several levels where you change around between the different menus by means of arrow

keys.

The complete list of menus is contained in the document “Menu operation via AKA 21”. (Cf. list

of literature).

PC operation

Operation takes place from a PC where Microsoft-Windows and System Software type AKM

have been installed. (The PC is connected to the system via Gateway type AKA 243/244).

Setting of the different functions is performed by means of rolling menus and dialogue boxes.

Settings can either be made via the keyboard or by using a mouse.

For users of AKM system software the complete list of menus is found in the document “Menu

operation via AKM”. (Cf. list of literature).

System information

Operation

There are three languages in the controller. Depending on the code number selected, the

languages are either: English, German and French or English, Danish and Spanish.

When the required language has been selected, the individual functions will be shown in this

language, both when there is operation via AKA 21 and system software type AKM.

NB! When you operate system software type AKM it is important that the language code is

set before an upload of the controller’s data is carried out to the AKM programme (it is the set

language that will be picked up by the AKM programme). Select one of the controller’s three

languages by means of the following settings:

0: English

1: German

2: French

3: Danish

4: Spanish

Activate the selected language by pushing "Enter" and then push "Clear".

Main Function Main Function Settings Language

___

Language

AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 5

The step regulator in the controller can control up to nine capacity steps that can be distributed

on one, two or more compressors. (The controller has a total of nine relay outputs that have to

be distributed between compressor steps and condenser steps).

Regulation

The cut in compressor capacity is controlled by the actual value of the suction pressure and

whether the pressure is rising or falling.

Regulation is performed by an I-controller when the compressors are cut in/out, and by a PI-

controller when they are controlled by means of speed regulation.

The user interface has been designed as for neutral zone setting.

- In the neutral zone there is no cut in/cut out of capacity steps.

- In the “+zone” and “-zone” bands cut in/cut out will depend on whether the pressure is rising

or falling. Cut in/cut out takes place with the selected time delays.

- In the “++zone” and “--zone” bands cut in/cut out takes place with the selected time delays.

- Refrigeration is stopped at pressures that are lower than the set “limit” value. (Cf. section on

“monitoring”).

- Cutin of steps is also adapted to the size of the next step to be cut in. A small step is cut in

earlier than a bigger one.

- Cutout of capacity steps is performed with a hysteresis corresponding to the smallest defined

capacity.

Regulation reference

Regulation is based on a set value which can be displaced with a number of functions to constitute

a general regulation reference. This general regulation reference is subsequently included in the

regulation together with the pressure measured by pressure transmitter P0.

The reference can be displaced in several different ways according to the required application.

Altogether the reference is composed of the following functions:

P0 SP Set reference

+ night setback Night setback value that can be started by two functions

1) Short-circuit of input “S6”

2) Internal time schedule

+ k1(EXT.REF./10) Value from external voltage signal

+ k2(t

a ref

-S6) Value from temperature signal

_________________

Total regulation reference

As equation:

Total regulation reference = P0 SP + Night Ref + k1 (EXT.REF./10) + k2(ta Ref - S6)

(The individual functions are described on the following pages).

NB!

When the night setback function is active, the contributions from the other functions will not be

included.

Capacity regulation of

compressor

6 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5

When regulation is performed, all functions are filtered over a period of time so that the

variation of the regulation reference is smoothed away. The change can be max. 0.2K/sec.

Set reference

Basic setting of suction pressure in °C.

Compressor Capacity Ctrl. Settings Compressor Ctrl. P0 SP

C___

Night setback

With this function the reference can be displaced by up to 25 K in a positive or negative direction.

(For night setback at a higher suction pressure a positive value must be set).

Compressor Capacity Ctrl. Settings Compressor Ctrl. Night Ref. K___

The function can be activated in three ways:

1) Short-circuit of the S6 input.

When the S6 input is short-circuited, the night setback function is activated.

2) A setting in the controller

Compressor Capacity Ctrl. Settings Compressor Ctrl. Forced Nght OFF/ON ___

(This setting can also be made from a master gateway’s override function).

3) Internal time schedule

The controller contains a clock function that can transmit a signal that will activate the night

setback function.

Start and stop times must be set for each day of the week.

Principle

AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 7

Definitions:

Night: Time when the night setback starts.

Day: Time when the night setback stops.

Night = 0 or Day = 0:

When one of the two times is set at 0, or when both are set at 0, there will be no night setback

the day and night in question.

Night = 1 and Day = 1:

When the two settings are set at the same time, there will be night setback throughout that day

and night.

Settings:

Compressor Capacity Ctrl. Special funct.Compressor Ctrl. Mo day h

___

Mo night h

___

Tu day h

___

Tu night h

___

We day h

___

We night h

___

Th day h

___

Th night h

___

Fr day h

___

Fr night h

___

Sa day h

___

Sa night h

___

Su day h

___

Su night h

___

8 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5

External voltage signal

Simple voltage signal

The voltage signal is sent to terminal “EXT.REF”. The voltage must be 0-10 V. With this signal

the reference can be displaced by up to 50 K in a positive or negative direction. 10 V provides

max. displacement. (K1 indicates the displacement in Kelvin at max. voltage = 10 V).

Reference displacement = k1(EXT.REF./10).

Compressor Capacity Ctrl. Special funct.Compressor Ctrl. P0 Ref. md = 1

Compressor Capacity Ctrl. Settings Compressor Ctrl. K1 Gain K ___

Measurement of relative humidity

Signals can be received from a separate electronic unit that registers the relative humidity. The

signal must be connected, as shown above, but other settings have to be made.

Reference displacement = k1(RH ref %/ 100 - EXT.REF./10).

Compressor Capacity Ctrl. Special funct.Compressor Ctrl. P0 Ref. md = 2

RH ref %

___

Settings Compressor Ctrl. K1 Gain K ___

If the external voltage input is not used, the function can be cancelled with setting K1 = 0. With setting

K1 = 10 there will be an influence of 0.1 K for each % the relative humidity changes (provided that

the moisture sensor’s signal is 0 V at 0% RH and 10V at 100% RH).

Temperature signal

A temperature sensor is connected to input S6.

A reference temperature is set in the controller. The temperature difference between the set

temperature and the measured temperature can now displace the reference by up to 10 K in both

positive and negative direction.

Reference displacement = k2(ta Ref.-S6).

Compressor Capacity Ctrl. Special funct.Compressor Ctrl. P0 Ref. md = 2

K2 Gain ___

ta Ref

C ___

AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 9

Limitations

When the reference is displaced by means of signals on the voltage input and the temperature

signal input, respectively, values for the permitted displacement must be set. Both a max. permitted

increase and a max. permitted decrease must be set. The values will not affect the value of the night

setback function.

Compressor Capacity Ctrl. Special funct.Compressor Ctrl. P0 Ref Max K ___

P0 Ref Min K ___

Neutral zone and regulating band

Neutral zone is set.

+zone and -zone bands are set.

Time delay in +zone and -zone band is set.

Time delay in ++zone and --zone band is set.

If all capacities are identical the set values are used. If the capacities however differ, the times

will apply to the average capacity in such a way that a small capacity is cut in faster and a big

capacity slower.

Compressor Capacity Ctrl. Settings Compressor Ctrl. NZ K

___

+zone K

___

+zone s

___

++zone s

___

-zone K

___

-zone s

___

- -zone s

___

Compressor definition

The controller can regulate up to nine compressor steps distributed on one, two or more

compressors. (If all nine steps are used for compressor control, there is no room left for the

control of condenser steps).

The controller can operate with capacity steps of varying sizes. In the definition of each capacity

step, the size of the capacity must be indicated with a percentage of the system’s total capacity.

The compressor steps must be defined in groups, so that the controller will know which steps

belong to compressor 1, which to compressor 2, etc. This definition is made by setting relay

outputs DO1 to DO9. Always use DO1 and up without skipping a relay output. If you skip one

or more, the showing of DI-alarms may cause problems.

For each relay output you select the compressor that is to belong to it. If several are selected

with the same compressor number, it will be the relay with the lowest number that stops and

starts the compressor. The subsequent relays will control the individual unloaders.

Output Configuration DO Relay No. ( ) DO( ) Type

= 1(1=compressor)

DO( ) Dev. No___

DO( ) Cap %___

The total capacity need not necessarily be 100% as long as it is close to 100%. The controller

itself calculates the value based on the defined values.

NB! If there are compressors with identical capacities, they must be set with the same value,

e.g. three identical units must be set with 33%, 33% and 33%.

Regarding infinitely variable speed regulation: See separate paragraph on page 20.

10 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5

Example:

A system consists of three compressors of the same size. One with three steps, and two without

steps.

The definition here is performed, as follows:

Output Configuration DO Relay No. 1 DO1 Type

= 1(1=compressor)*

DO1 Dev. No

= 1

DO1 Cap % = 11

DO Relay No. 2 DO2 Type

= 1(1=compressor)

DO2 Dev. No

= 1

DO2 Cap % = 11

DO Relay No. 3 DO3 Type

= 1(1=compressor)

DO3 Dev. No

= 1

DO3 Cap % = 11

DO Relay No. 4 DO4 Type

= 1(1=compressor)*

DO4 Dev. No

= 2

DO4 Cap % = 33

DO Relay No. 5 DO5 Type

= 1(1=compressor)*

DO5 Dev. No

= 3

DO5 Cap % = 33

The three relay outputs marked with a * will start and stop the compressors, and the others will

cut in and cut out the unloaders.

Time delays for cut ins and cut outs

To protect the compressor motor against frequent restarts, two time delays can be set.

- a minimum period which shall pass from a compressor starts till it can be restarted.

- a minimum period (on-time), during which the compressor must be operating, before it can be

stopped again (to avoid a cutout before the suction pressure has had time to become stable).

The setting ranges are from 0 to 25 minutes.

If the output is used for cutins and cutouts of unloaders, the settings will automatically be

zeroset.

Output Configuration DO Relay No. ( ) DO( ) Recy m ___

DO( ) ON m ___

Sequence for cut in and cut out of capacity

The sequence for cut in and cut out of capacity can be defined in two ways. Either there is a

fixed defined sequence, or the controller itself checks the defined capacity size and then

defines the sequence. The sequence will be established by the following setting:

1. Sequential (step mode = 1).

In general the numbers with which the different compressors are defined will establish the

sequence for the cut ins (the compressor defined with a low number will start before a

compressor with the next number).

The sequence for the cut outs will furthermore be established by the compressor type:

Compressors with one step

The sequence is not changed (last cut in step will be cut out first, when the required

capacity drops again).

Compressors with several steps

When there are cut outs, the steps on the borderline between the two compressors will

be changed around. The function will produce the effect that the last started compressor

will not stop until the control has cut out the “last” step of the previous compressor.

AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 11

Example:

Cut in Cut out

2. Automatic equalisation of operating time or capacity-based regulation (Step mode = 2).

With this setting the controller itself examines whether the set capacity steps are of the same

size, or whether they differ in size.

When the capacity steps have been defined to be

identical

The compressor performs an automatic equalisation of operating time between the compres-

sors.

- At the different starts, the compressor with the lowest amount of run time will be started

first.

- At the different stops, the compressor with the highest amount of run time will be

stopped first.

- For compressors with several steps there will be no changes of the steps, as is the case

with sequential cut ins and cut outs.

- For compressors with more steps, there can only be one compressor at a time with cut-

out unloaders.

When all capacity steps have

not

been defined to be identical:

The controller now registers the actual capacity steps according to size. The controller will

subsequently cut in and cut out the individual capacity steps, so that the calculated capacity

requirement is covered in the best possible way.

If a part of the compressors of the same size without unloaders have been defined, these

compressors will take part in a rota arrangement, so that the operating times are equalised.

Compressor Capacity Ctrl. Settings Compressor ctrl. Step Mode

1 / 2

12 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5

Signal from the compressor's safety controls

The controller requires a signal on the status of each compressor’s safety circuit. The signal

taken directly from the safety circuit is connected to a “DI” input. This input is a 230 V a.c. input.

(The safety circuit must stop the compressor without the help of AKC 25H5).

If the safety circuit is broken, the controller will cut out all output relays for the compressor in

question and give an alarm. The other compressors will continue the regulation. (A broken

circuit at the DI input will interrupt the output).

An input from a compressor and the compressor’s number are defined.

Input Configuration Alarm input No. 1..9 DI( ) Type

= 1(1=compressor)

DI( ) Dev. No. ___

(compressor No.)

A time delay has to be defined in connection with all alarms. It covers the period of time from

the cut out moment until the alarm is registered.

Input Configuration Alarm input No. 1..9 DI( ) Del. m ___

The alarm message concerning a failure in the safety circuit can be extended into a more

concrete message by using alarm module type AKC 22H. Read the later section on

monitoring.

Hourmeter

The run time of a compressor motor is constantly registered. It can be shown on the display

how many hours the compressor has been operating since the hourmeter was last reset, and

how many starts there have been during the past 24 hours. (About resetting, see later).

Compressor status Compressor No.( ) ( ) Run time

Compressor status Compressor No.( ) ( ) Cut / 24 h

All relay outputs are registered by a counter. The run time is registered here for whatever has

been connected to the output. This registration can be shown on the display, and reset, if

required.

Output Configuration DO Relay No.( ) DO( ) Time h

The hourmeter range is from 0 to 30,000 hours.

AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 13

Temperature sensor

The controller has three inputs for temperature measurements. Their application is primarily, as

follows:

S6: Reference displacement of suction pressure and/or night setback signal when the input is short-

circuited.

S7: Reference control of the condensing pressure with a temperature signal from the condenser’s

inlet air.

S8: Reference temperature for a heat recovery function utilising the condenser heat.

Depending on whether the inputs are used for their primary purpose or not, the registered

measurements may be logged.

Only if the S6 input is used for a night setback signal is simultaneous logging of data not possible.

If the sensors are used for random temperature registration, which is not their primary function, no

alarm message will be sent in case of a sensor error.

The service function is used for displaying the temperature values.

Service mode Measurements of input terminals S6

Forced control of compressor capacity

There can be forced control of the capacity where the normal regulation and the safety

function are disregarded. The capacity is set in per cent of the regulated capacity.

Compressor Capacity ctrl. Settings Compressor ctrl Man. Cap OFF/ON

Man. Cap. % ___

Compressor control, but no condenser control

The controller is normally used for controlling both the compressor and the condenser. If the

controller is only used for controlling the compressor, a missing signal at the pressure

transmitter input Pc will trigger an alarm signal. To avoid this alarm, a signal can be picked up

from pressure transmitter PO. Connect terminal 72 to 76 (“s” to “s”). The monitoring function for

PCmax must be set at the highest possible value.

Peak load limitation

The controller has an input that can receive signals from other automatic controls when they register

a max. limit value for the momentary power consumption.

When the controller input “LOAD SHED” is short-circuited, it will start a function in the regulation

ensuring that the cut-in compressor capacity will not be higher than a set value. This value is set

as a percentage of the whole compressor capacity.

Compressor Capacity Ctrl. Special funct.Compressor Ctrl. Load Shed %___

If further adaptation of the capacity is required, the input can be fitted with, say, a

potentiometer.

- when R < 50 ohm the capacity will be as mentioned above.

- when 50 < R < 1000 ohm the capacity will be linear between the set value and 100%

capacity.

- when R > 1000 ohm the function will be inactive

Liquid injection into the suction line

14 Function description RC.1J.53.02 © Danfoss 06/2000 AKC 25H5

The pressure gas temperature can be kept down by means of liquid injection into the suction line.

The function is controlled on the basis of the superheat measured by Ss and Po. Two values are

set in the controller: Max. superheat and a value for when liquid injection has to be started. The

value is set as the difference from the set max. superheat.

Re valve connection: Read the section “Valve function” on page 22.

Compressor Capacity Ctrl. Special funct.Compressor Ctrl. Inj. Diff. K ____

AKC 25H5 Function description RC.1J.53.02 © Danfoss 06/2000 15

The step regulator in the controller can control up to nine capacity steps that may be

distributed on one or more condensers. (The controller has nine relay outputs that may be

distributed between compressor steps and condenser steps).

Regulation

The cut in condenser capacity is controlled by the actual value of the condensing pressure,

and on whether the pressure is rising or falling.

Regulation is performed by a I controller when the condenser fans are cut IN/OUT, and by a PI-

controller when they are controlled by means of speed regulation.

The user interface has been designed as for neutral zone setting.

- In the neutral zone there is no cut in/cut out of capacity steps.

- In the “+zone” and “-zone” bands cut in/cut out depends on whether the pressure is rising or

falling.

Cut in/cut out takes place with the selected time delays.

- In the “++zone” and “--zone” bands cut in/cut out takes place with the selected time delays.

- Cutin of steps is also adapted to the size of the next step to be cut in. A small step is cut in

earlier than a bigger one.

- Cutout of capacity steps is carried out with with a hysteresis corresponding to the smallest

defined capacity.

Regulation reference

The reference for regulation can be defined in two ways. Either as a fixed set reference or as a

reference that varies according to the outdoor temperature.

Fixed set reference

The reference function is defined and the condensing pressure set in °C.

Condenser Capacity Ctrl. Special function Condenser Ctrl. PcRef.md. =

Condenser Capacity Ctrl. Settings Condenser Ctrl. Pc SP

___

Capacity regulation of

condenser

Variable reference

This function permits a change of condensing pressure reference within a defined range. A basic

value for the condensing pressure is set, and a max. and a min. limit based on this value are set.

The reference function is defined with setting Pc Ref. md. = 2.

Condenser Capacity Ctrl. Settings Condenser Ctrl. Pc SP

___

Condenser Capacity Ctrl. Special function Condenser Ctrl. PcRef.md. =

Condenser Capacity Ctrl. Pc Ref Max K ___

Pc Ref Min K ___

NB! When the heat recovery function is used, this function may raise the reference, so that it will

be higher than the set max. value.

Within the set limits the condensing temperature can now vary, based on contributions from 3

functions. These functions will all be included in the regulation reference and subsequently in the

regulation, and be compared to the pressure measured by pressure transmitter Pc.

PC ref = min

+ variable contribution + S7 temperature + contribution from the TC function.

All changes of the reference are filtered over a period of time, so that the change is distributed on

this period (this, however, does not apply to changes of set values). The period of time is set in

minutes.

Condenser Capacity Ctrl. Special function Condenser Ctrl. Pc Ref Del m ___

1. The condensing pressure is reduced as a function of the cut-in compressor capacity.

It is based on:

- dimensioned condenser capacity (temperature difference between air temperature and

condensing temperature)

- how large a part of the compressor capacity has been cut in

Set the required temperature differential (min. tm) at minimum load (fx 7 K). Set the dimensioned

differential (dim tm) at maximum load (fx 15 K). The controller will now contribute with a value

to the reference that depends on how large a share of the compressor capacity has been cut

in.

Condenser Capacity Ctrl. Special function Condenser Ctrl. min. tm K

___

dim. tm K

___

Cut-in

compressor capacity

2. The condensing pressure is reduced as a function of the outdoor temperature

A sensor is connected to the S7 input.

The temperature value is used directly in the reference. When the measured temperature rises

by one degree, the condensing temperature is increased by one degree.

3. The condensing pressure is reduced as a function of the expansion valve's opening degree (Tc

signal)

The function can be used in systems where controllers with a Tc output type AKC 114D-116D

have been installed.

All the relevant Tc outputs are connected in series and then connected to AKC 25H5, so that

it will receive a 230 V signal.

When the expansion valve on one of the connected controllers opens so much that it reaches

a set opening degree, it will break the signal.

The reference for the condensing temperature will then start rising, and hence increase the

system’s capacity. When a signal is again received at the Tc input, this will result in a drop of

the reference value.

If regulation is carried out with a variable reference and the Tc function is

not

used,

230 V a.c.

must

be connected to the Tc function’s terminals.

Neutral zone and regulating band

The neutral zone is set.

The +zone and -zone bands are set.

The time delay for the +zone and -zone bands is set.

The time delay for the ++zone and --zone bands is set.

If all capacities are identical the set values are used. If the capacities however differ, the times

will apply to the average capacity in such a way that a small capacity is cut in faster and a big

capacity slower.

Condenser Capacity Ctrl. Settings Condenser Ctrl. NZ K

___

+zone K

___

+zone s

___

++zone s

___

-zone K

___

-zone s

___

- -zone s

___

Condenser definition

The controller can control several condenser steps that are cut in and out sequentially.

The condenser steps must be defined in a sequence so that the controller will know which

output belongs to condenser step 1, which output to condenser step 2, etc. The individual

compressor steps will control the capacity defined for the output, and they will be cut in and out

in sequence. The steps defined with the lowest number will be cut in first, then the step defined

with a higher number, etc. Cut out takes place in the opposite sequence. Thus, the last cut in

step will be cut out first.

Output Configuration DO relay No. ( ) DO( ) Type 2

(2=condenser)

DO( ) Dev. No

DO( ) Cap % ___

Re speed regulation: Read the separate paragraph on page 20.

Example:

A system consists of three condenser steps. Here the definition can be made, as follows:

Output Configuration DO relay No. ( ) DO5 Type

= 2 (2=

condenser

)

DO5 Dev. No

= 2

DO5 Cap % = 33

DO6 Type

= 2 (2=

condenser

)

DO6 Dev. No

= 1

DO6 Cap % = 33

DO9 Type

= 2 (2=

condenser

)

DO9 Dev. No

= 3

DO9 Cap % = 33

Here the cut in and cut out sequence will be, as follows: 1, 2, 3 - 3, 2, 1.

I.e., the relay outputs will be activated in this sequence: DO6, DO5, DO9 - DO9, DO5, DO6.

Time delays for cutins and cutouts

Output Configuration DO Relay No. ( ) DO( ) Strt m ___

DO( ) ON m ___

Once a day (at 13:00 hrs) all steps will be activated for one minute.

Signal from the condenser's safety controls

The controller can receive signals on the status of each condenser step’s safety circuit. The

signal is taken directly from the safety circuit and is connected to a “DI” input.

This input is a 230 V a.c. input.

If the safety circuit is broken, the controller will cut out the output relay for the relevant step and

give an alarm. The remaining steps will continue the regulation. (A broken connection on the

DI input will cut out the output).

An input from a condenser step and the number of the condenser step are defined.

Input configuration Alarm input No. 1..9 DI( ) Type

= 2 (2= condenser)

DI( ) Dev. No. ___

A time delay must be defined for the period from the alarm is registered until it is transmitted.

Input Configuration Alarm input No. 1..9 DI( ) Del. m ___

Hourmeter

The run time of the different outputs is registered by a counter. This registration can be

displayed and reset, if required.

Output Configuration DO Relay No.( ) DO( ) Time h

The hourmeter’s range is from 0 to 30,000 hours.

Forced control of condenser capacity

Forced control of the capacity can be arranged, where the normal regulation is disregarded.

The capacity is set in per cent of the regulated capacity.

Condensor Capacity ctrl. Settings Condenser ctrl. Man. Cap OFF/ON

Man. Cap. % ___

Condenser control, but no compressor control

The controller is normally used for controlling both compressors and condensers. If the

controller is only used for controlling condensers, a missing signal from pressure transmitter

input PO will trigger an alarm signal. To avoid this alarm, a signal may be picked up from

pressure transmitter Pc. Connect terminal 72 to 76 (“s” to “s”). The monitoring function for

POmin is now set at the lowest possible value.

One of the defined capacity steps for either the compressor regulation or the condenser regulation

can be linked up with a speed regulation that for example can be a frequency converter type VLT

(Compressors with step unloading

cannot

be speed-regulated).

The DO9 output is defined the normal way, with indication of the connected capacity and the setting

determining whether it is a compressor or a condenser that is to be regulated. The output is

connected to the frequency converter’s ON/OFF input, and the analog “AO” output for the frequency

converter’s analog input is connected at the same time.

The ON/OFF signal will start and stop the frequency converter, and the analog signal will indicate

the speed.

Two values must be set in the motor control - one for the max. speed and another for the min.

speed. They are both based on the nominal value, the max. value being, say, 1.3 times the

nominal value and the min. value, say, 0.8 times the nominal value.

When the step is in operation it will consist of a fixed capacity and a variable capacity. The

fixed capacity will be the one that is cut in when the frequency converter starts up, and the

variable capacity will lie in between the min. and max. speed. To obtain the best possible

regulation the variable capacity must be bigger than the “biggest gap” to be covered during

regulation. (The “gaps” will typically be bigger during sequential operation than during binary

operation, as the binary operation will itself find the optimum cutin/cutout pattern. If there are

many short variations in the system’s capacity requirement it will increase the need for

variable capacity.

The definition is based on the capacity produced by the compressor at max. speed. This value

is now used in conjunction with the system’s other capacity for determining the setting of the

step’s capacity.

Example: Three compressors of 5, 5, and 10 kW, respectively, where the 10 kW unit is speed-

regulated at between 0.8 and 1.3 times the nominal speed. The capacity here will be 1.3 x 10

= 13 kW. This will give a setting of 56% (13 x 100/(5+5+13) = 56).

Min. capacity at 0 V must be defined, as follows:

The setting is a value based on the step’s min. capacity seen in relation to the step’s max.

capacity. It can be calculated in the following manner:

Value = min. speed/max. speed (e.g. 0.8/1.3 = 0.62).

This is how steps are cut in and out

Speed regulation

Max.

Nominel

Min.

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Danfoss Compressor pack controllers type AKC 25H5Vers. 1.3x Installation guide

Danfoss Compressor pack controllers type AKC 25H5Vers. 1.3x Installation guide

Danfoss Compressor pack controllers type AKC 25H5Vers. 1.3x Installation guide

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