ADAP-KOOL 25 H7 Function description 06-2001.… · For users of AKM system software the complete...

Function description

ADAP-KOOL®

RC.1N.P1.02 ��RC.1N.P2.02 06-2001

Controller for capacity regulationof brine installation

AKC 25H7

2 Function description RC.1N.P2.02 © Danfoss 06/2001 AKC 25H7

This function description is make out in June 2001 and applies to AKC 25H7 with code num-bers 084B2022 and 084B2023

Validity

Contents

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

Application ......................................................................... 3

Systeminformation ............................................................. 4

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

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

Application ............................................................................ 5

Control of cold brine temperature ....................................... 6

General description ........................................................... 6

Control reference .............................................................. 6

Capacity regulation of compressor .................................... 9

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

Hourmeter ....................................................................... 12

Forced control of compressor capacity ........................... 12

Other functions belonging to the compressor operation13

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

Accumulation of ice ......................................................... 13

Compressor control, - but not condenser control ............ 13

Injection signal ................................................................ 13

Start-up procedure .......................................................... 14

Defrost ............................................................................. 14

Pump control ....................................................................... 16

Cold side ......................................................................... 16

Warm side ....................................................................... 17

Control of warm brine temperature ................................... 18

General description ......................................................... 18

Control of condenser temperature .................................. 18

Control of heat recovery .................................................. 20

Limitations ....................................................................... 21

Examples of setup of references and limitations............. 21

Capacity regulation of condenser ..................................... 23

Choice of system structure .............................................. 23

Regulation ....................................................................... 24

Neutral zone .................................................................... 25

Fan definition ................................................................... 25

Time delays for cutins and cutouts .................................. 25

How to prevent that fans get stuck .................................. 25

Signal from the fans’ safety controls ............................... 26

Hourmeter ....................................................................... 26

Forced control of condenser capacity ............................. 26

Condenser control, but not compressor control .............. 26

Use of special functions..................................................... 27

Thermostat function ........................................................... 27

Monitoring............................................................................ 28

Monitoring of maximum discharge pressure ................... 28

Monitoring of minimum suction pressure ........................ 29

Monitoring of temperatures ............................................. 30

Monitoring of ON/OFF functions ..................................... 31

Sensor failure .................................................................. 32

General information ............................................................ 33

Supply voltage ................................................................. 33

Function switch (Main Switch) ......................................... 33

Clock function .................................................................. 33

Access codes .................................................................. 34

Refrigerant ....................................................................... 35

Service ................................................................................ 36

Measurements ................................................................. 36

Forced control of outputs ................................................ 36

System measurements/data .............................................. 37

AKA 21 operation ............................................................ 37

PC operation ................................................................... 37

Forced control of outputs ................................................ 37

Alarms and messages ........................................................ 38

The importance is indicated by means of the follow ....... 38

This is how the various messages are transmitted: ........ 38

Who are the alarm receivers? ......................................... 39

Example of setup of controller .......................................... 40

Connections ........................................................................ 44

Survey of the controller's terminals ................................. 44

Brief description of the individual terminals ..................... 45

Technical data ..................................................................... 46

Dimensions .......................................................................... 46

Ordering ............................................................................... 47

Installation considerations ................................................ 47

List of literature ................................................................... 47

AKC 25H7 Function description RC.1N.P2.02 © Danfoss 06/2001 3

Introduction ApplicationAKC 25H7 is a complete brine cooler control unit that has been developed for indirectrefrigerating systems in supermarkets.AKC 25H7 can be used together with other controllers from Danfoss’ programme of ADAP-KOOL® refrigeration control system.

The controller’s main function is to control compressors and condensers in such a way that therequired brine temperature is maintained on the cold and warm side of the compressor system.

The controller contains all the functions required for the control of a brine cooler:• The cold brine temperature can be controlled according to the shop temperature or the

enthalpy

• Day/night programmes for the temperature reference (economy control)

• Alarm limits and delays on forward and return flow temperatures

• Capacity control and monitoring of compressors distributed on one or two groups

• Sequential control or time equalisation of compressors

• Frost cutout for monitoring of suction pressure P0

• Peak load limitation via external signal

• Central defrost control or weekly programme (stop based on temperature or time)

• Signal given when injection is permitted

• Control and monitoring of single pump or twin pump on cold and warm brine

• Built-in operating time equalisation between twin pumps

• Automatic pump change when pump is defective

• Control and monitoring of air-cooled or brine-cooled condenser

• Condenser can be controlled based on pressure (Pc) or warm brine temperature (S7)

• Monitoring of max. condensing pressure

• Step regulation or speed regulation of fans

• Condensing pressure can be controlled according to outdoor temperature and an external

voltage signal

• Control of heat recovery temperature with built-in safeguard against too low condensing

pressure

• Heat recovery temperature can be controlled according to outdoor temperature and an

external voltage signal

• Monitoring of the compressors’ safety circuit can be supplemented with alarm module type

AKC 22H

The controller’s terminals are shown at the end of the document.


SysteminformationController type AKC 25H7 is a unit in the ADAP-KOOL® refrigeration control system. Thecontroller can be linked up with other controllers in the system via a two-core connection - theDANBUSS Data Communication. Through this connection information can be transmittedbetween the units, like settings, measurements, alarms etc.

Remote serviceThe different messages and alarms can, via the telephone network, be transmitted by modemsto, say, a service company.

Address codingAn 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 theinstallation instructions for the data communication cable (literature No. RC.0X.A).

Connection of control panel type AKA 21A plug for the connection of control panel AKA 21 is mounted right on the front plate of AKC25H7. (If the control panel is to be used in any other place, a terminal box will have to beinstalled (cf. the installation instructions for the data communication cable, literature No.RC.0X.A).)

Data communicationTo obtain correct data communication it is important that the installation instructions for the datacommunication cable be adhered to (literature No. RC.0X.A).

OperationThe controller can be operated in two different ways. Either by using control panel type AKA 21or by means of a PC with system software type AKM.

AKA 21 operationSetting of the different functions is performed via a menu system. The menu system is built upon several levels where you change around between the different menus by means of arrowkeys.

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

PC operationOperation takes place from a PC where Microsoft-Windows and System Software type AKMhave 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 “Menuoperation via AKM”. (Cf. list of literature).

LanguageThere are three languages in the controller. Depending on the code number selected, thelanguages are either: English, German and French or English, Danish and Swedish.When the required language has been selected, the individual functions will be shown in thislanguage, 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 setbefore an upload of the controller’s data is carried out to the AKM programme (it is the setlanguage that will be picked up by the AKM programme). Select one of the controller’s threelanguages by means of the following settings:0: English1: German2: French3: Danish6: SwedishActivate the selected language by pushing "Enter" and then push "Clear".


The control has been designed for one of the following three applications:

1 Control of one compressor group based on “S4” and one condenser based on “Pc” (Appl. Mode = 1).

Used where the condenser is air-cooled, or where there is one brine-cooled condenser.

2 Control of one compressor group based on “S4” or one or two condensers based on brinetemperature “S7”. Pc used for monitoring (Appl. Mode = 2).

Used where one or more condensers are brine-cooled and connected to the same brinecircuit.

3 Control of two compressor groups according to “S4” and two condensers based on brinetemperature “S7” (Appl. Mode = 3)

Used where there are two separate compressor groups.

In addition to the three basic applications, further functions may be selected, as mentionedearlier in the introduction.

Setting: INPUT Configuration - Application mode - Appl. Mode_____

Application

Hint!The controller can also be used in systems with direct expansion and application modes 1 and2. The heat exchanger and S4 are not mounted, so regulation will take place based on P0. (S4must not be used and the alarm destination for S4 must be set to 0).


General descriptionAKC 25H7 controls the cut-in compressor capacity, so that the temperature at the sensor (S4 orP0) corresponds to the reference temperature. The actual regulation of the compressors takesplace by means of a neutral zone controller which adjusts the cut-in compressor capacity to theactual load of the connected cooling/freezing points.

• AKC 25H7 can control and monitor one or two compressor groups with max. 11 compressorsteps distributed on max. eight compressors.

• The suction pressure is constantly monitored and protects the evaporator against freezing.• AKC 25H7 can control and monitor two twin pumps.• AKC 25H7 contains functions that will ensure a correct correlation between compressors,

pumps and injection when the system is started.• Central defrost.

Control referenceRegulation of the cold brine temperature (S4 or P0 in connection with DX application) takesplace on the basis of a reference value comprising a set value plus a number of functions thatwill be added to this value. Displacement functions are used for adjusting the referencetemperature to the actual load.

Cold Ref = Cold SP Set value (setpoint)+ DT.Night Contribution from day/night function+ K1 x (U Cold - UrefCold)Contribution from external voltage signal, if applicable+ K2 x (S3 - Tref Cold) Contribution from S3 temperature, if applicable

All changes of the reference (except for the night setback function) are filtered over a period oftime, so that there will be no “leaps” in the reference.

In order to prevent that the reference value becomes too high or too low, limiting factors can beput in.

Below we give you a description of the individual contributions and the limitation function:

Set valueSetting of setpoint value for S4 (P0) temperature:Setting: Compressor Capacity Ctrl. - Cold Temp. Control - Cold SP__

Contribution from day/night functionWith this function the reference can be displaced by up to 25 K in positive or negativedirection. When a night lid is placed on the appliances, the load will drop considerably, andthe function may therefore be used for raising the brine temperature during the night.The function can also be used for cold accumulation when the brine temperature has to belowered during periods where the price of electricity is low.The relay output DO9 can be defined to follow the controller’s day/night function. During thenight the output will be activated.

Setting: Compressor Capacity Ctrl. - Cold Temp. - Dt.Night K ___If the function is not to be used, arrange setting = 0.

Control of cold brinetemperature


The function can be activated in two ways:

1) Signal on NIGHT inputWhen 230 V is fed to this input, the night setback function will be activated.

2) Internal time scheduleThe controller contains a clock function that can transmit a signal that will activate the nightsetback function.Start and stop times must be set for each day of the week.

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 setbackthe 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 thatday and night.

Setting: Day/Night Clock - Day/Night Setting - Mo day h ___ (+more)


Contribution from an external voltage signalWith a 0 - 10 V d.c. voltage signal on the U COLD input the reference can be displaced byup to 50 K in positive or negative direction.The signal may be supplied from a transmitter or another general control giving a signal onthe air’s enthalpy or relative humidity.

Setting: Compressor Capacity Ctrl. - Cold Temp. Control - K1 ___ , UrefCold V___

If the function is not to be used, set K1 at 0.

Example:- Brine reference to be displaced based on the air’s relative humidity.- A transmitter is mounted in the shop which measures the air’s relative humidity in the

range 0 - 100%, corresponding to an output signal of 0 - 10 V d.c.

- At 60% relative humidity no displacement of the reference will be required (60% relativehumidity corresponds to an output signal of 6 V, i.e. Uref Cold = 6).

- For each 10% increase of the relative humidity (corresponding to 1 V), the referenceshould be lowered by 2 K, that is to say, K1 = - 2

The contribution to the reference will therefore be: -2 (“voltage signal at Ucold input” - 6).

Contribution from a temperature signalWith this function it is possible to displace the reference on the basis of a measuredtemperature S3. The sensor can for instance be placed in the brine’s return flowtemperature or on the business premises. A reference is obtained in this way which shouldbe adjusted to the actual load.

Setting: Compressor Capacity Ctrl. - Cold Temp. Control - K2 ___ , TrefCold °C___

If the function is not to be used, set K2 at 0.

Example:- Brine reference temperature to be displaced based on the shop temperature.- At 18°C no displacement of the reference is required, i.e. TrefCold = 18.- For each 1°C increase of the shop temperature the reference should be lowered by 1 K,

i.e. K2 = -1.The contribution to the reference will therefore be: -1 (“S3 signal” - 18).


Limitation of referenceTo prevent that the sum of the contributions from day/night, voltage signal and temperaturesignal will result in a too big displacement, a permissible working range must be stated forthe reference. This is accomplished by setting a max. permissible reference and a min.permissible reference.

Both the max. value and the min. value are set as absolute values.Setting:C ompressor Capacity Ctrl. - Cold Temp. Control - Cold Max°C ___ , Cold Min°C___

Capacity regulation of compressorThe step regulator can control up to 11 capacity steps distributed on max. eight compressors.This controller has been designed, so that the connected compressor steps are the same size,but this is not a requirement.

The cut-in compressor capacity is controlled by the actual brine temperature measured with theS4 sensor and based on whether the temperature is rising or falling. Or with the P0 pressuretransmitter if S4 has not been mounted, for instance in connection with control of a system bymeans of direct expansion.

The control is performed by a neutral zone controller.- 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 temperature is

rising or falling. Cut ins/cut outs takes place with the selected time delays.- In the “++zone” and “--zone” bands cut in/cut out takes place with the selected time delays,

whether the temperature is rising or falling.

Settings:Neutral zon is set+ Zone and - Zone bands are setTime delay in +Zon e and - Zone band is setTime delay in ++Zone and –Zone band is set

Compressor Capaciy Ctrl. - Compressor Step Control - NZ___ , etc.

Compressor definitionAll the relay outputs can be used for compressors and fans, but you may also select a thirdfunction which is specific for the given output.It is necessary, for example, to clarify which of these special functions are to be used beforeoutputs for compressors and fans can be selected. Reference is made to the paragraphabout the use of special functions.

The controller can control one or two compressor groups with up to 11 compressor stepsdistributed on max. eight compressors.

When relay outputs for compressors are fitted, it must be defined by means of the setting: DOType = “1” (fan defined with “2” and special functions with “3”).


Each compressor must be defined with a number, and this is done with setting DO Dev. No.”_”(“1” is used for compressor number 1, “2” for compressor number 2, and so on).

For compressors with several steps the relay outputs belonging to the same compressor mustbe defined with the same number. The controller knows in this way which step belongs to agiven compressor. Based on the same settings the controller will then use the relay output withthe lowest number for starting and stopping the compressor.Setting: OUTPUT Configuration - DO Relay No.1 - DO1Type___

- DO1Dev.No___

Example:A system consists of three compressors. One compressor with three steps and two compressors with one step each. Definition is carried out,as follows:

OUTPUT Configuration DO Relay No.1 DO1 Type = 1 (1 = compressor)DO1 Dev. No = 1(compressor 1, step 1)

DO Relay No. 2 DO2 Type = 1 (1 = compressor)DO2 Dev. No = 1(compressor 1, step 2)

DO Relay No. 3 DO3 Type = 1 (1 = compressor)DO3 Dev.No = 1 (compressor 1, step 3)

DO Relay No. 4 DO4 Type = 1 (1 = compressor)DO4 Dev.No = 2 (compressor 2, step1)

DO Relay No. 5 DO5 Type = 1 (1 = compressor)DO5 Dev.Nro= 3 (compressor 3, step1)

If the controller is to control two groups of compressors (A and B), there are two things to beconsidered.- The controller’s use must be defined for two groups (“Application mode” must be set at “3”).- The compressors’ numbers must be defined on the basis of the following requirements:

Odd numbers must belong to group A (DO Dev No. = 1, 3, 5 etc.).Even numbers must belong to group B (DO Dev No. = 2, 4, 6 etc.).

Example:System consisting of two groups. Each group consists of two compressors. One compressor with two steps and one compressor with one step.The definition can be made, as follows:

“Application mode” to be set at “3”.

OUTPUT Configuration DO Relay No.1 DO1 Type = 1 (1 = compressor)DO1 Dev. No = 1(compressor A1, step 1)

DO Relay No.2 DO2 Type =1 (1 = compressor)DO2 Dev. No =1 (compressor A1, step 2)

DO Relay No.3 DO3 Type = 1 (1 = compressor)DO3 Dev. No=2 (compressor B1, step 1)


DO Relay No.5 DO5 Type = 1 (1 = compressor)DO5 Dev. No=3 (compressor A2, step 1)


Time delay for cutins and cutoutsTo protect the compressor motor against frequent cutins and cutouts two time delays can be putin.- A minimum restart time (min. time between two starts).- A minimum ON time (min. operating time before the compressor can be stopped again.

The time delays only apply to start and stop of the compressor motors. The outputs controllingthe cutin and cutout of the unloaders will not be affected.

The setting range is 0 - 25 minutes.

Settings:

OUTPUT Configuration - DO Relay No.( ) - DO( ) Recy m____ , DO( )ON m___


Sequence for cutin and cutout of capacityThe sequence for cutin and cutout of compressor capacity can be defined in two ways. Eitherwith a fixed sequence or automatic equalisation of the operating time between thecompressors.

1) Sequential cutin and cutout (Step Mode = 1)CutinCutin of compressor capacity will take place in the sequence defined for the compressors.The compressor with the lowest “DO() Dev. No.” number will be started before the compres-sor with the subsequent number.If compressors with several steps are included, all steps of one compressor will be cut inbefore the next compressor is started.

If the controller has been set to control two compressor groups, cutin of the compressorcapacity will take place alternately between groups A and B, so that there will be an evendistribution of capacity between the two groups. Within the individual group cutin ofcompressor capacity will still take place in the sequence defined for the compressors.

CutoutThe sequence for cutout of compressor capacity will depend on the compressor type:- Compressor with one step

Last step cut in will be the first cut out.- Compressors with several steps

At cutout the steps on the border between the two compressors will be reorganised. Thisfunction sees to it that the last cut-in compressor will not stop until the previous compressorhas cut out one unloader.

- Compressor groupsIf two compressor groups are used, cutout of the steps will take place alternately betweengroup A and group B. Within the individual group cutout of compressor capacity will followthe rules described above.

2) Automatic equalisation (Step mode = 2):With this setting the controller will perform an automatic operating time equalisation betweenthe compressors.- The compressor with the lowest number of operating hours will be cut in first.- The compressor with the highest number of operating hours will be cut out first.

Cut in Cut out

Cut in Cut out


- For compressors with several steps there will be no reorganisation of the steps, as the caseis for sequential coupling. The result is that there will only be one compressor at a time withcut-out unloaders.

- If two compressor groups are used, equalisation of the operating time will take place withineach group, but not between the groups.

Settings:

Compressor Capacity Ctrl. - Compresssor Step Control - Step Mode___

Signal from the compressor's safety controlsAll digital alarm inputs (DI1 - DI8) can be used for monitoring of compressors and fans, or forthe individual inputs a third function. This third function is specific for a given input. In otherwords, the use of these specific functions must be clarified before inputs for the compressors(and fans) are selected. Refer to the paragraph about special functions).

The controller must have a signal on the status of each individual compressor’s safety circuit.The signal is taken directly from the safety circuit and connected to a digital alarm input (DI1 -DI8). The digital alarm inputs DI1 - DI8 are all 230 V a.c. inputs.

If the compressor’s safety circuit is cut out, the controller will cut out all output relays for thecompressor in question and give alarm (for the sake of safety the safety circuit must stop thecompressor without the assistance of AKC 25H7). Regulation continues for the remainingcompressors.

When a digital alarm input is mounted, the purpose must first be defined. When a compressorhas to be monitored, the setting must be “1” (i.e. “DI( )Type” = 1 for the input in question).

Then the compressor’s number must be set:DI( )Dev. No. = 1 (Here the input will monitor compressor No. 1).DI( )Dev. No. = 2 (Here the input will monitor compressor No. 2).

Thirdly, a time delay has to be set. The time delay counts from the time the safety circuit is cutout and until AKC 25H7 reacts to the alarm.

Settings:INPUTConfiguration - Setting of Alarm input 1..8 - DI( )Type___ , DI( )Dev.No___ , DI( )Del. s___ etc.

HourmeterAn hourmeter is attached to all relay outputs. The hourmeter registers the time the output inquestion has been activated since it was last zeroset. The hourmeter range is from 0 to 30,000hours.Readout/Setting:

OUTPUT Configuration - DO Relay No.( ) - DO( ) Time____

Forced control of compressor capacityThere can be forced control of the capacity where the normal regulation and the safety functionare disregarded. The capacity is set in per cent of the regulated capacity.Setting:Compressor Capacity Ctrl. - Compressor Step Control - Man.Cap___, Man Cap. %____


Peak load limitationThis function may limit the energy consumption during certain periods where the cut-in capacitymust be kept below a certain level. The level is set as a per cent of the total compressorcapacity.The limitation is active when the LOAD SHED input is shortcircuited.This activation of the input must be performed by other controls which monitor the actualenergy consumption.Setting:Compressor Capacity Ctrl. - Compressor Step Control - LoadShed. %____

Accumulation of iceThe analog “AO” output will provide a 0 to 10 V signal, if the output is not used for controllingthe condenser capacity. The signal will then represent the cut-in compressor capacity (0 to100%). The signal may be used by other automatic controls, e.g. for controlling theaccumulation of ice.

In periods where the price of electricity is low and the compressor capacity not fully utilised, forexample, other automatic controls may allow accumulation of ice.

Compressor control, - but not condenser controlThe controller is normally used for controlling both the compressor and the condenser. How-ever, if the controller is only used for controlling the compressor, a lack of signal to pressuretransmitter input PcA may produce the result that the alarm will sound. But the alarm functionmay be cancelled by setting the alarm destination for “PcA/P0B” and “HP Max” at 0. Pleaserefer to the section named alarms and messages.Settings:Alarm destinations Sensor Alarms PcA/PoB = 0 (0= No alarm)

Other Alarms HP Max = 0 (0=No alarm)

Injection signalInjection into the evaporator must be synchronised with the compressor operation. The injectionmust start at the same time as the first compressor starts, and it must stop at the same time asthe last compressor stops.The DO7 and DO6 outputs have been prepared for synchronisation of the injection.DO7 is used for compressor group A (one or two compressor groups).DO6 is used for compressor group B (only two compressor groups).A voltage signal is via output DO connected to either the solenoid valve or the relay activatingthe injection control on an AKC 24P (or AKC 24P2).

But in those cases where the controller’s outputs are used for other functions, the signal maybe generated in other ways.- Either directly from the compressor relay, if sequential cutin and cutout of the compressor is

used.- Or in the following way, if time equalisation is used between the compressors (when there is

time equalisation, it is not known which compressor will start first/stop last:All relays that start/stop the compressor must have an auxiliary switchAll auxiliary switches from the same compressor group must be connected in parallel.

Other functions belongingto the compressoroperation


A voltage signal is via the in-parallel connected auxiliary switches connected to the solenoidvalve or to the relay activating the injection function on AKC 24P/AKC 24P2.

The outputs are defined, as follows:DO6 is set to Type = 3 (injection signal B)DO7 is set to Type = 3 (injection signal A)

Start-up procedureThe controller contains functions ensuring a correct interaction between pumps, compressorsand injection during start-up.

PumpsDuring start-up the pumps must accelerate a large amount of brine to normal flow velocity,before the compressors are allowed to start.A time delay of 60 seconds has therefore been built into the controller, the time delay requiredbefore the first compressor can start.The time can only be changed via software type AKM.

Capacity limitationIf too much compressor capacity is cut in during the start-up phase, the compressors will dropout on low pressure. To prevent this, a time delay of 120 seconds has been placed between thefirst and the subsequent capacity step.The time can only be changed via software type AKM.

InjectionThe signals from DO6 and DO7 will not release the injection until the suction pressure hasdropped to a value which will ensure that the compressors are not overloaded. The injection willonly be released at a suction pressure corresponding to a value of 5 K above the referencevalue for the cold brine temperature.The value can only be changed via software type AKM.

DefrostThe controller can carry out central defrost of the whole cold brine circuit. When a defrost isinitiated, the compressors will stop, but the pumps will continue to circulate the cold brine.Defrost can be stopped based on time, or when the cold brine has reached a set temperature.When the defrost has stopped, the compressors will start again.

Relay output DO8 can be defined to follow the defrost function. The output will then beactivated during the defrost:Define relay output DO8 to follow the defrost function by means of the setting: Type = 3.


Defrost startDefrost can be started in three ways:

1. Manual defrostManual defrost is started via control panel AKA 21 or a PC. The setting automatically returnsto OFF when the defrost has been completed.Start with the setting: Man.Def. = ON

2. Signal on input DEFRWhen 230 V a.c. is received on input DEFR, the defrost will start. The signal must be a pulsesignal of at least 2 sec. duration. If the external signal remains active 30 minutes after theresumption of refrigeration, there will be an alarm. The alarm is cancelled, when the defrostsignal is removed.

3. Internal time scheduleDefrost is started via a weekly programme which has been set in the controller. The timesrelate to the controller’s clock function.Use of the time schedule is defined with setting: Def.Sched. = ON.

Three individual time schedules with up to four defrosts each may be programmed. Next,define which weekdays are to follow which schedule.

Schedule 1 No. Per Day.Def 1 Sc1 Hour

Min

Def 2 Sc1 HourMin

etc.


Minetc.


Minetc.

Def. Schedule Day selection Mon Sched. 1/2/3Tue Sched. 1/2/3etc.

Defrost stopYou may choose between two kinds of defrost stop:

1. Stop based on temperature with time as a safety factor.The temperature of the cold brine is measured here. When the temperature is equal to theset stop temperature, the defrost will stop, and cooling will be resumed.

You may choose whether defrost stop is to be based on the S4 or the S3 temperature.

If the defrost time exceeds the set max. defrost time, the defrost will stop. This will happen,even if the temperature for defrost stop has not been reached. At the same time as thedefrost is stopped, the alarm message “Defrost time exceeded” will appear. The alarm willstop automatically after five minutes.Settings:Defrost Control -Defrost stop Method Temp/Time____ (1= stop on temperature)

MaxDef Time___Def.Stop °C___DefStop Sx___

2. Stop on timeA fixed defrost time is set here. When this period of time has elapsed, the defrost will stopand cooling will be resumed.Settings:Defrost Control -Defrost stop Method Temp/Time____ (2 = stop on time)

MaxDefTime___


Cold sideThe controller can control and monitor one or two pumps circulating the cold brine. If twopumps are used and equalisation of operating time is selected, the controller can also alternatebetween the two pumps in case of operational alarms.

Connection and definition

- Cold pump 1 must be connected to relay output DO1.- If a cold pump 2 is connected, it must be to relay output 3.- The outputs must be defined, so that the controller knows that they are used for pumps. DO(1

and 3, if applicable): Type is set at 3 (3 = cold pump).

Choice of pumpIt is possible to choose:- whether one of the pumps should operate- whether both pumps should operate, or- whether you want to alternate between the pumps (then there will be equalisation of operating

time and change-over to the other pump, if the first one fails)Choice of pump is carried out with the following settings:0: both pumps are stopped1: pump 1 put into operation2: pump 2 put into operation3: both pumps put into operation4: automatic change-over between pumps allowedSetting:Pump Control - Pump Cold Brine - CPump Ctrl___

Automatic change-over between the pumps (only when setting = 4). With this setting theoperating times of the two pumps will automatically be equalised. Set the required workingperiod for the pump. When this working period has elapsed, the other pump will be started. (Atstart-up is is however always pump 1 which starts).When you change over to the other pump, the inactive pump will be started before the activepump is stopped. Set the required overlap time.

Setting:Pump Control - Pump Cold Brine - CPumpDel.s___Pump Control - Pump Cycle - PumpCycl.h___

Monitoring of pumpsGeneralIf the controller is to monitor the pump operation, the controller’s digital alarm input DI1 mustbe connected to a signal from, for example, a flow switch.It has to be input DI1, as this is the only input which can be used for the cold brine pumps. Ifthe input is used for monitoring the pumps, the input must be defined by means of setting“4” (DI1 Type = 4).A time delay for when the alarm is to be activated must also be set. The time delay is theperiod of time between the moment the input loses the signal and the controller’s alarm.

Especially where there is equalisation of operating time whenthe pumps are operating with automatic equalisation of operating time, the controller willcarry out a change-over between pumps when the flow is insufficient (the change of pumpwill however not take place until the time delay for the alarm has expired). Depending onwhether the change of pump cancels the alarm situation or not, the following will happen:

1) Change of pump will cancel the alarm situation.If the change of pump cancels the alarm situation, the faultless pump now operating willkeep on running until the normal cycle has ended. Now change back to the “faulty pump”,as it must be presumed that it has been repaired. At the same time zeroset the alarm

Pump control


situation (alarm is cancelled). If the faulty pump has not been repaired, another alarm willbe released, and there will be another change-over to the faultless pump. This processwill be repeated, until the situation has been remedied.

2) Change of pump does not cancel the alarm situation.If the alarm however remains active after the change of pump, the controller will also givean alarm for the other pump. At the same time, both pump outputs are activated in anattempt to create so much flow that the alarm situation will be cancelled. The controllerwill now have both pump outputs activated until the alarm signal disappears.

Separate alarm priorities can be set for drop-out of one pump and for drop-out of bothpumps. Please read the section named Alarms and Messages.

Warm sideThe controller can control and monitor one or two pumps circulating the warm brine. The controland monitoring is in principle the same as mentioned in the section about cold brine, but thereare a few exceptions as regards the connections - they are, as follows:- Hot pump 1 must be connected to relay output DO2.- If a warm pump 2 is connected, it must be to relay output DO4.- The outputs must be defined, so that the controller knows that they are used for pumps. DO(2

and 4, if applicable): Type set at 3 (3 = warm pump).- If the controller is to monitor whether the warm brine pumps are operating, the controller’s

digital alarm input DI2 must be connected to a signal from, for example, a flow switch.It has to be input DI2, as this is the only input which can be used for the warm brine pumps.

Setting:Pump Control - Pump Warm Brine - WPump Ctrl___

Pump Warm Brine - WPumpDel.s___Pump cycle - PumpCycl.h___


General descriptionAKC 25H7 can control air-cooled as well as brine-cooled condensers. Capacity control can takeplace with various functions, e.g. step coupling or speed control of fans and control of a by-passvalve.During normal operation the cut-in condenser capacity will then control the cut-in condensercapacity, so that the condensing temperature measured with S7 or with Pc sensor willcorrespond to the reference temperature.During heat recovery the cut-in condenser capacity will then control the forward flowtemperature (Saux), so that the warm brine is adjusted to the actual load in the heat recoverycircuit.The condenser pressure, expressed either by Pc or S7, is monitored constantly, and it isensured that the pressure will not exceed the min. and max. limits (also during heat recovery).AKC 25H7 can control and monitor two twin pumps (refer to section “Pumps”).

Control of condenser temperature

ReferenceThe condenser temperature is controlled by the S7 or Pc sensor, depending on the applicationchosen.Control takes place according to a reference value consisting of a set value (setpoint) and avariable contribution from an external voltage signal.Warm Ref.°C = Warm SP°C + K3 (U warm - UrefWarm).When K3 is an amplification factor, U warm is the voltage signal to the controller, and the lastlink is the value against which the voltage signal should be compared.

The contribution from the voltage signal is filtered over a period of time, so that there will no“leaps” in the reference.

It is possible to have the condenser temperature follow the outdoor temperature, so that it as aminimum will always have a fixed differential above the outdoor temperature (measured withSout).(Warm Ref°C > Sout + Min tm K).

Finally it is possible to limit the condenser temperature with absolute max. and min. limits.

A description of the settings and limitations to the references is given below.

Set value (setpoint)Set the basic value of the referenceSetting: CondenserCapacity Ctrl. - Warm Temp. control - Warm SP°C__

Control of warm brinetemperature


Contribution from an external voltage signalWith a 0 - 10 V d.c. voltage signal on input “U WARM” the reference can be displaced byup to 50 K in positive or negative direction. The signal can be supplied from a transmitteror another general control unit.

Settings: Condenser Capacity Ctrl. -Warm Temp. control - K3___ , UrefWarm V___If the function is not to be used, arrange setting K3 = 0.

Limitation of reference:Absolute max. and min. limits

To avoid that the condenser pressure becomes too high or low, max. and min. limitscan be set.

These max. and min. limits will also apply to heat recovery.Settings: Condenser Capacity Ctrl. -Warm Temp. control - Pc/S7 Max°C___ , Pc/S7 Min°C___

In relation to the outdoor temperatureIt is possible to have the condenser reference follow the outdoor temperature, so thatit as a minimum will always be a few degrees above the outdoor temperature(measured with Sout). The result is that if the outdoor temperature rises to thereference value for the condenser temperature, the reference value will be raised bythe set value. The value could for instance be the temperature differential accordingto which the condenser or brine cooler has been dimensioned.The advantage of this function is that it permits a smaller cut-in fan capacity in therange with partload.The function cannot displace the reference above the set max. limit.

Settings: Condenser Capacity Ctrl. -Warm Temp. control - Min tm K___If the function is not used, setting should be -25K.


Control of heat recoveryDuring normal operation the condenser temperature is controlled according to S7 or Pc. Whenheat recovery is activated, the reference is changed, and the controller will now control on thebasis of the Saux sensor.

Activation of heat recoveryThe heat recovery function must be activated by a signal on input DI8 (230 V a.c.). The DI8input must be defined, so that it can be used for the heat recovery function.Setting: INPUT Configuration - Setting of Alarm input 1..8 - DI 8 Type 4 (4 = heat recovery)

Definition of outputRelay output DO11 can be defined to follow the heat recovery function. The output can forinstance start a pump in the heat recovery circuit when the heat recovery function is active.Setting: OUTPUT Configuration - DO Relay No. 11 Type 3 (3= Heat recovery)

ReferenceWhen the heat recovery function is activated, the controller changes reference sensor to Saux.At the same time the reference value is changed, as follows:

Heat Ref°C = Warm SP°C Set setpoint+ Dt Heat K Contribution from heat recovery function+ K4 (Uwarm - UrefWarm) Contribution from voltage signal+ K5 (Sout - TrefWarm°C) Contribution from outdoor temperature

The contributions from the external voltage signal and the Sout temperature are filtered over aperiod of time, so that there will no “leaps” in the reference.

The reference value for the heat recovery is indirectly limited inasmuch as the limitations on thecondenser temperature are also active during heat recovery.

The three contributions are the following:- Contribution from the heat recovery function

With this function the reference can be displaced by up to 50 K in positive direction.

Setting: Condenser Capacity Ctrl. - Warm Temp. control - Dt Heat K___

- Contribution from external voltage signalWith a voltage signal of 0 - 10 V d.c. on the “Uwarm” input the reference can be displacedby up to 50 K in positive or negative direction. The signal will typically come from anoverriding control unit. Please note: it is the same voltage signal which is part of thereference for the condenser temperature (the only difference being the constant K4). Thecontribution can be expressed, as follows: K4(Uwarm - Uref warm).

Setting: Condenser Capacity Ctrl. - Warm Temp. control - K4___ , UrefWarm___If the function is not used, set K4 to 0.


- Contribution from outdoor temperatureThe function is used for displacing the brine’s forward flow temperature (Saux) in relationto the outdoor temperature. As the need for heat recovery normally depends on theoutdoor temperature, the function will adjust the heat recovery temperature to the actualload. The contribution is: (Sout - TrefWarm°C).

Setting: Condenser Capacity Ctrl. - WVarm Temp. control - K5___ , TrefWarm°C___If the function is not used, set K5 to 0.

LimitationsWhen the heat recovery function is activated, the controller, as mentioned, will control theforward flow temperature of the warm brine (Saux), but the controller also still controls thecondenser temperature (S7 or Pc). So if one of the set nax./min. values is exceeded, thefollowing will happen:

Pc/S7 max. limitationThe controller will control the condenser temperature (Pc/S7) with a reference corresponding tothe “Pc/S7 Max.” value.The controller will change back to the Saux reference when the condenser temperature (Pc/S7)again drops below “Pc/S7 Max.”.(The heat recovery output DO11 will not be cut out at any time).

Pc/S7 min. limitationThe controller cuts out the heat recovery output DO11 if the condenser temperature dropsbelow the min. limit, i.e. the pump in the heat recovery circuit will be cut out.The controller will continue working according to Saux.

The heat recovery is restarted when the condenser temperature has risen to 2 K above thelimitation temperature.

Examples of setup of references and limitations

Example 1

Requirements to control of condenser temperature (Pc/S7). / Setting- The condenser temperature must be controlled by the outdoor temperature. The brine cooler is

dimensioned, so that there will as a minimum be a temperature differential of 5 K between the outdoortemperature and the brine temperature. / Setting: Min tm K = 5 K.

- The reference temperature must be 15°C. / Setting: Warm SP°C = 15°C.- The reference temperature must not exceed 35°C. / Setting: Pc/S7Max°C = 35°C.- An external voltage signal is used for displacing the reference. / Setting: K3 = 0.

Requirements to control of heat recovery. / SettingHeat recovery function to be used. / Setting: DI8 Type = 4.- Reference for Saux temperature to be 30°C. / Setting: Dt Heat K = 15 K.- It must be possible to displace the reference with an external voltage signal:

0 V must give a displacement of 0 K. / Setting: UrefWarm = 0 V.10 V must give a 10 K displacement. / Setting: K4 = 1.0.


- Heat recovery not to be compensated in relation to the outdoor temperature. / Setting: K5 = 0.- Output DO11 is used for start and stop of the pump in the heat recovery circuit. / Setting: DO11 Type = 4.- Heat recovery to be cut out, if the condenser temperature (Pc/S7) drops below 10°C. / Setting: Pc/

S7Min°C = 10°C.

By inserting the above settings in the formulation of the references, you obtain:- Warm Ref°C = 15°C- Warm Ref°C > Sout + 5K- Heat Ref°C = 30°C + 1.0 x Uwarm- The condenser temperature is furthermore limited between 10 and 35°C.

Example 2

Requirements to control of condenser. / Setting- Condenser temperature to be controlled on the basis of a setpoint of 20°C /

Setting: Warm SP°C = 20°C- The reference must not be overridden by the outdoor temperature. / Setting: Min tm K = -25K- There is no overriding from an external voltage signal. / Setting: K3 = 0

Requirements to control of heat recovery. / Setting- Heat recovery function is to be used. / Setting: DI8 Type = 4- DO11 output to be used for start and stop of the pump in the heat recovery circuit. / Setting: DO11 Type = 4- Reference for heat recovery to be 35°C. / Setting: Dt Heat K = 15 K- There is no overriding from an external voltage signal. / Setting: K4 = 0- Heat recovery to be compensated in relation to the outdoor temperature:

The displacement must be 0 K at 18°C. / Setting: TrefWarm°C = 18 °CFor each 10°C reduction of the outdoor temperature, the heat recovery must be increased by 4 K. /Setting: K5 = -0,4

- When the heat recovery function is activated, the condenser temperature must not exceed 40°C or bebelow 15°C. / Setting: Pc/S7Max°C = 40°C and Pc/S7Min°C = 15°C.

By inserting the above settings in the formulation of the references, you obtain:- Warm Ref°C = 20°C- Heat Ref°C = 35°C - 0.4 (Sout - 18°C)- The condenser temperature is furthermore limited between 10 and 40°C.

Pc/S7 Max.

Warm SP

Pc/S7 Min.

Heat RefWarm Ref °C

Pc/S7Max.

Warm SP

Pc/S7Min.

Heat Ref°CWarm Ref °C


Choice of system structureRegulation of the condenser capacity can be accomplished in various ways. The type ofregulation is defined through setup of analog output “AO”.Choose between one of the following options:1. Condenser capacity controlled exclusively by the fans’ step regulation. (AO Type = 1).

The condenser capacity is controlled exclusively by the fans defined on the DO outputs (theanalog output ”AO” will produce a voltage between 0 and 10V corresponding to the cut-incapacity).

2. The capacity is regulated by means of a 0 to 10V signal in one of the following two ways(AO Type = 2):

a) Speed control of fans

A 0 - 10V signal is picked up from analog output “AO”.The min. and max. speeds of the fans are set in the frequency transformer.

b) Control of by-pass valve (three-way valve) and step regulation of fans

The lower end of the capacity regulation is handled by the by-pass valve, and stepregulation of the fans will not start until the valve is completely closed.A 0-10V signal is downloaded from the analog output ”AO” for control of the valve.The fans are controlled via the DO outputs.

Capacity regulation ofcondenser

Capacity

Capacity

Capacity

By-pass

Closed

Open

Heatrecovery

PI-control ofby-pass valve

NZ control offans


3. The capacity is controlled by a combination of by-pass valve action and speed regulation of fans.(AO Type = 3)

The 0 - 10 V signal from analog output “AO” is used here both by the by-pass valve and thespeed regulation for the fans:0-5 V is used for the by-pass valve5-10 V is used for the speed regulationThe lower end of the capacity regulation is handled by the by-pass valve, and speedregulation of the fans will not start until the valve is completely closed.The min. and max. speeds of the fans are set in the frequency transformer.

NB. In the chosen frequency transformer it must be possible to define that 5 V correspondsto the minimum speed of rotation.

4. Inverted AO signal. (AO Type = 4)This setting gives an inverted function of the linear signal shown under ”AO Type = 2”

RegulationThe condenser capacity is controlled by the actual condenser or heat recovery temperature.

When the controller regulates the capacity with the by-pass valve or by means of speedregulation, the controller will function as a PI regulator. Here it will constantly try to adjust thecapacity so that the temperature will correspond to the reference temperature.

When the controller controls the capacity by means of step regula-tion of the fans, the controllerwill function exclusively as a neutral zone regulator.

- When the temperature is outside the neutral zone, there will be no cutin or cutout of fans.- If the temperature is in the + zone or - zone, the cutin and cutout of fans will depend on

whether the temperature is rising or falling.- If the temperature is in the ++ zone or the -- zone, the cutin and cutout of the fans will take

place whether the temperature is rising or falling.

Capacity

By-pass

Closed

Open

Heatrecovery

PI-control ofby-pass valve

PI-control offans


A function has been incorporated in the controller which adjusts the time delays for cutins andcutouts of fans. The time delays depend among other things on the deviation between theactual temperature and the required temperature. If the deviation between the actualtemperature and the reference is big, the controller will operate with short time delays. If thedeviation is small, the controller will operate with longer time delays.The time delay is defined at the transition to the +zone and –zone.Setting: Condenser Capacity Ctrl. - Warm Temp. control - Zone delay___

Neutral zoneThe width of the neutral zone will affect the time delays for cutin and cutout of fans. The width ofthe neutral zone should therefore not be set at a too high or too low value. Normally a neutralzone width of 2 to 5 K will be appropriate.Setting: Condenser capacity Ctrl. - Condenser Step Control - NZ K___

Fan definitionAll the relay outputs can be used for compressors and fans, but you may also select a thirdfunction which is specific for the given output.

It is therefore necessary to clarify which of these special functions are to be used beforeoutputs for compressors and condensers are selected. Please read the paragraph about theuse of special functions.When relay outputs for fans are set up, they must be defined with the setting: DO Type = “2”(compressors are defined with “1” and special functions with “3”).

The fans must be defined in the sequence in which they are to be cut in and out. The fan withthe lowest “DO()Dev.No.” will be cut in first. Then follows the fan with the following number, etc.Cutout takes place in the opposite sequence. Consequently, the last cut-in step will be cut outfirst.

Example:A system with three fan steps can be defined, as follows:

OUTPUT Configuration DO Relay No. 5 DO5 Type = 2 (2 = fan)DO5 Dev. No = 2

DO Relay No. 6 DO6 Type = 2 (2 = fan)DO6 Dev. No. = 1

DO Relay No. 9 DO9 Type = 2 (2= fan)DO9 Dev. No. = 3

This will give the following cutin and cutout sequence: DO6-DO5-DO9, DO9-DO5-DO6

Hint:As the first cut-in fan in some fan units has a much greater effect than the last one, it would bean advantage to divide the fans into groups. In this way we obtain a better regulation of thecapacity. E.g.:

1st step: 1 fan2nd step: 2 fans3rd step: 4 fans4th step: 8 fans5th step: etc.

Time delays for cutins and cutoutsValues for minimum ON and OFF times for fans cannot be defined. In the controller greaterimportance has been attached to the accuracy of the regulation than to the start/stop sequencefor the fans.

How to prevent that fans get stuckIf a fan is never started for a long period of time, there is a risk that it will get stuck. To preventthis, the controller contains a function that will check once a day (around noon) whether the fanoutputs have been activated during the past 24 hours. The fan outputs which have not beenactivated will then be activated one by one (for five seconds each).


Signal from the fans’ safety controlsAll digital alarm inputs (DI1 - DI8) can be used for monitoring of fans or compressors, but for afew inputs there can be a third function. The third function is specific for a given input. Thismeans that the use of these specific functions has to be clarified before inputs for fans (andcompressors) are selected. Please read the paragraph about use of special functions).

The controller can receive signals about the status of each condenser step’s safety circuit. Thesignal is obtained directly from the safety circuit and connected to a digital alarm input (DI1 -DI8). The digital alarm inputs DI1 - DI8 are all 230 V a.c. inputs.

If the safety circuit is cut out, the controller will cut out the output of the fan and give an alarm(for reasons of safety the safety circuit must stop the fan without the assistance of thecontroller). Regulation is carried on with the remaining fan steps.

When digital alarm inputs are set up, the purpose must first be defined. When a fan has to bemonitored, the setting must be “2” (i.e. DI( ) Type = 2 for the input in question).

Then the number of the step to be monitored must be set:DI()Dev.No=1 (Here the input monitors step 1)DI()Dev.No=2 (Here the input monitors step 2)

Thirdly, a time delay has to be set. The time delay applies from the moment the safety circuit iscut out and until AKC 25H7 gives alarm.Settings: INPUT Configuration - Setting of Alarmi input 1...8 - DI ( )Type___ , DI( )Dev.No___ , DI( ) Del. s___

HourmeterAn hourmeter is attached to all relay outputs. The hourmeter registers the time the output inquestion has been activated since it was last zeroset.The hourmeter range is from 0 to 30,000 hours.Setting: OUTPUT Configuration - DO Relay no.( ) - DO( ) Time___

Forced control of condenser capacityThere can be forced control of the capacity where the normal regulation and safety function aredisregarded. The capacity is set in per cent of the total capacity.Setting: Condenser capacity Ctrl. - Condenser Step Control - Man Cap. ON/OFF , Man Cap. %___

Condenser control, but not compressor controlThe controller is normally used for controlling both compressors and condensers. If the control-ler is only used for controlling condensers, a lack of signal on the pressure transmitter side POAmay produce the result that the alarm is sounded. To avoid this, the alarm destinations for thePO alarm and the suction pressure alarm “LP Min” may be put in pos. “0”.Settings:Alarm destinations Sensor Alarms P0A = 0 (0= no alarm)

Other Alarms LP Min = 0 (0=no alarm)


Use of special functions All relay outputs DO1 to DO11 and digital alarm inputs DI1 to DI8 can be used for compressorsand fans.But beyond that there are special functions belonging to a certain output/input. The use of thesespecial functions must be clarified before outputs and inputs for compressors and fans areselected.In the survey below the special functions are shown in the last two columns:

Output Type 1 Type 2 Type 3 Type 4DO1: Comp. Fan Cold pump 1DO2: Comp. Fan Warm pump 1DO3: Comp. Fan Cold pump 2DO4: Comp. Fan Warm pump 2DO5: Comp. FanDO6: Comp. Fan Injection function BDO7: Comp. Fan Injection function ADO8: Comp. Fan DefrostDO9: Comp. Fan Night setbackDO10: Comp. Fan ThermostatDO11: Comp. Fan Heat recovery

DI1: Comp. Fan Other monitoring Cold pump 1 and 2DI2: Comp. Fan Other monitoring Warm pump 1 and 2DI3: Comp. Fan Other monitoringDI4: Comp. Fan Other monitoringDI5: Comp. Fan Other monitoringDI6: Comp. Fan Other monitoringDI7: Comp. Fan Other monitoringDI8: Comp. Fan Other monitoring Heat recovery on/off.

The controller contains a separate thermostat function which may be used, as required. It is forexample capable of starting a fan in the compressor room, if the temperature exceeds a setvalue.

It is possible to select thermostat sensor and cutin and cutout limits, but it is only output DO10that can be defined to follow the thermostat function’s ON/OFF performance.

The sensor is defined with settings 1 to 7:1) PoA2) PcA/PoB3) S34) S45) S76) Sout7) SauxSetting: INPUT Configuration - Thermostat input sensor - Th.Sensor___

Relay output DO10 is defined to follow the thermostat function with setting Type = 3.Setting: OUTPUT Configuration - DO Relay No. 10 - DO10 Type___

Thermostat settings:- Thermostat's cutin value in °C- Thermostat's cutour value in °CSettings: Thermostat / Temp. Alarms - Thermostat - ThCutin°C____ , ThCutout°C___

Thermostat function


Monitoring of maximum discharge pressure (safety function)The function cuts in condenser steps and gradually cuts out compressor steps, if thecondensing pressure exceeds the permitted value. The cut out limit can be defined in the rangebetween -30 and +70�C.The condenser pressure is measured with:- PcA, if the controller only controls one compressor group (S7, if a pressure transmitter is not

mounted).- S7, if the controller controls two compressor groups.

The function starts at a value that is 3 K below the set value. At this point the entire condensercapacity is cut in at the same time as half of the compressor capacity is cut out. The alarmfunction is activated. There is now a 30 second wait and if the pressure is still in the criticalrange, half of the actual compressor steps are again cut out. This continues until the pressurehas dropped below the critical limit or all compressor steps have been cut out.

If the temperature (pressure) rises to the set limit value, the following happens:- all compressor steps are immediately cut out- the condenser capacity remains cut in

The alarm ceases when the following conditions are complied with:- the temperature (pressure) has dropped to the 3 K below the limit value for 60 seconds- the time delay has expired (see later).

Renewed cut in of compressor steps is allowed when the following conditions are compliedwith:- the alarm has stopped (the time delay has expired)- the time delay for “Minimum time between start of compressors” has expired (adjustable).- the time delay for restart has expired (next paragraph).

Setting: Safety functions - Limits with 1. Priority- HP Max°C ___

Monitoring

HP Max.

Alarm

Cond. Cap.

Comp. Cap.


Monitoring of minimum suction pressure (safety function)The function immediately cuts out all compressor steps if the suction pressure becomes lowerthan the permitted value. The cut out limit can be defined in the range between -70 and +30�C.The suction pressure is measured with:- P0A, if the controller controls one compressor group- P0A and PcA/P0B, if the controller controls two compressor groups. (A cutout of a compressor

group will immediately produce the result that the lost capacity will be cut in in the othercompressor group).

Cut outs activate the alarm function.

The alarm ceases when the following conditions are complied with:- the pressure (temperature) is above the cut out limit- the time delay has expired (see later).

Renewed cut in of compressor steps is allowed when the following conditions are compliedwith:- the alarm has stopped (the time delay has expired)- the time delay for “Minimum time between start of compressors” has expired (adjustable).- the time delay for restart has expired (see below)

Setting: Safety functions - Limits with 1. Priority - LP Min°C ___

Time delay for restartThe time delay for restart is common to the two safety functions.

After a cutout the compressors cannot be cut in again, until the time delay period has expired.The time delay can be defined in the range between 0 and 30 minutes.Setting : Safety functions - Limits with 1. Priority - Restart m ___

LP Min.

AlarmComp.

HP Max

LP Min


Monitoring of temperaturesThe function will sound the alarm if the set temperature limits are exceeded on the followingsensors: S3, S4 and Saux.Reference: Thermostat / Temp. Alarms - S( ) Temperaturalarms

It is possible to set alarm limits for high and low temperature:Setting: Thermostat / Temp. Alarms - S( ) Temperature alarms - High S( )°C____ , Low S( )°C____

An alarm will be given if the set limit is exceeded, but not until the time delay period hasexpired. Three time delays have to be set (in minutes):- For too high temperature:

High1Del.m: Time delay for restart and after defrostThe time delay will apply until the actual temperature has dropped belowthe upper alarm limit.

High2Del.m: Time delay during normal regulation.- For too low temperature:

Low Del.m: Time delay during normal regulation.Setting: Thermostat / Temp. Alarms - S( ) Temperature alarms - High1Del.m___ , High2Del.m___ , LowDel.m____

Example

High / Low Alarm limit for high temperature and low temperatureS: Alarm ceases

Curve 1: Cooling stage(1): time delay "High1Del.m" has been exceeded. Alarm becomes active.

Curve 2: Normal regulation where the temperature becomes too high(2): time delay "High2Del.m" has been exceeded. Alarm becomes active.

Curve 3: Temperature becomes too low(3): Time delay "Low Del.m" has been exceeded. Alarm becomes active.

High

Low

High1Del.m High2Del.m Low Del.m


Monitoring of ON/OFF functionsThe controller is provided with eight digital alarm inputs DI1 - DI8. Some of the inputs are usedfor compressors, condenser steps, pumps, etc. The remaining inputs may be used for otherpurposes to the extent required.

Various elements in the compressor’s safety circuitA simple monitoring of compressors, condensers andpumps has been described in the respectiveparagraphs, but the monitoring of a compressor can beextended from being a simple monitoring process todifferentiated monitoring of several elements of thesafety circuit.

This will require that the controller is linked up with analarm module type AKC 22H. This alarm module willthen receive signals from the different elements of thesafety circuit, and in this way deliver an accurate reportas to where in the circuit the problems can be found.

The connection must be established in this way:

The connections and the individual alarm messages are fixed and cannot be changed:- Compr. No ( ) oil press. cut out (too low oil pressure)- Compr. No ( ) current cut out (motor overload cut out)- Compr. No ( ) motor prot. cut out (too high temperature in motor winding)- Compr. No ( ) disch. temp. cut out (too high pressure gas temp.)- Compr. No ( ) disch. press. cut out (too high discharge pressure)

- Compr. No ( ) safety cut out (signal missing from alarm module)- Compr. No ( ) not in auto (switch in manual mode)Carry out the settings mentioned in the earlier section “Signal from compressors safetycontrols”.

All alarm modules are double, i.e. one module can monitor two safety circuits. Each circuit isconnected to a DI input on AKC 25H7.


Other purposesIf an input is used for monitoring other automatic controls, the input in question must be set to“DI Type” = 3. An alarm text may then be chosen which is to be transmitted when the input iscut out. Choose between the following texts when setting:Setting: INPUT Configuration - Setting of Alarm input 1...8 - DI( ) Type = 3 (3 = other alarm monitoring)DI( ) Dev.No.___ 1: Olil pressure fault

2: High pressure fault3: Low pressure fault4: Fan fault5: Phase fault6: Low liquid level7: Liquid flow switch8: Refrigerant leak

Time delays are defined for the individual alarm inputs.Setting: INPUT Configuration - Setting of Alarm input 1...8 - DI( ) Del. m___

Sensor failureIf a missing signal from one of the connected temperature sensors or pressure transmitters isregistered, an alarm will be given.Normally the functions attached to the defective/missing sensor will disappear. But in certaincases the controller will try to maintain the function by using alternative sensors.

Defect on S4:If a defect arises on sensor S4, the controller will instead use suction pressure P0 for capacityregulation of the compressors. The result will be that the cold brine temperature will rise by acouple of degrees.If there are defects on both S4 and P0, the entire compressor capacity will be cut out.

Defect on Pc or S7:If Pc is used as regulating sensor for the condenser and defects arise on it, the controller willinstead use S7. The controller will then control the S7 temperature based on a reference whichis 5 K below the normal reference.If S7 is used as regulating sensor for the condenser and defects arise on it, the controller willinstead use pressure measurement Pc. The controller will then control the Pc temperaturebased on a reference which is 5 K above the normal reference.If there are defects on both S7 and Pc, the controller will cut in the entire condenser capacity.


Supply voltageThe controller must be supplied with 230 V a.c., with live connected to terminal No. 2. It is arequirement that the controller has earth connection. It is installed at the terminal next to themains connection.

In the controller there is a built-in 1 A slow-blowing Ø5 x 20 mm fuse.

Function switch (Main Switch)The controller has two functions that can start and stop the regulation.- A function switch inside the unit that can be set via the control function.- An external input that can be connected to a switch.

InterntalThe switch has three positions:- Normal regulation (setting = +1)- Regulation stopped (setting = 0)- Service function. (setting = -1)Setting: Main Function - Main function settings - Main switch +1/0/-1

If the switch is set in pos. 0 or -1, all the controller’s functions are inactive. An alarm with thetext “Standby mode” is generated to indicate that regulation has stopped. If the switch is in pos.+1, regulation has started

ExterntalIf the external function switch is used, a switch for the “Main Switch” input must be connected. Ifit is not used, the input must be shortcircuited. There are two menu groups that only can beset when the MAIN SWITCH input is interrupted. The two groups are the following: “InputConfiguration” and “Output Configuration”.

The combination of internal and external switch is, as follows:- Regulation is only carried out when both switches are in pos. ON (internal = +1 and external =

shortcircuited).- Service settings can be made when the internal switch is put in pos. “Service Function”

(setting = -1) External = shortcircuited.- All other combinations will stop the regulation.

Clock functionThe controller contains a clock function. Setting of days, hours and minutes can be performedhere.AKC 25H7 Adr: -- Clock day: 1-7 (1=Monday, 7=Sunday)AKC 25H7 Adr: -- Clock hour: 0-23AKC 25H7 Adr: -- Clock min: 0-59

Note:If the controller is connected to an installation with gateway, type AKA 243/244, the gateway willreset the clock function after a power failure.

General information


Access codesThe controller can be operated with system software type AKM and control panel type AKA 21.Both operating modes may give access to several levels, depending on the user’s knowledgeof the various functions.

System software type AKM:The different users are defined here with initials and passwords. Access is now granted toexactly the functions the user is allowed to operate.The operation is described in the AKM manual.

Control panel type AKA 21:Access can be given to three user levels here:1) Access without use of password.

See alarms. Display selected temperatures. Start defrost.2) Access via code 1

Setting of selected functions, acknowledgement of alarms.3) Access via code 2

All settings in the menu system can be performed.The operation is described in “Menu operation via AKA 21”.

If access code is set in pos. “0” (factory setting), there is free access to the system without theuse of a password.AKC 25H7 Adr.: -- Chg. Code1 ___

Chg. Code 2 ___


Before regulation can be commenced, the refrigerant must be defined.You may select one of the following refrigerants:1 R12 9 R500 17 R5072 R22 10 R503 18 R402A3 R134a 11 R114 19 R404A4 R502 12 R142b 20 R407C5 R717 (ammonia) 13 User-defined 21 R407A6 R13 14 R32 22 R407B7 R13b1 15 R227 23 R410A8 R23 16 R401A

The refrigerant is selected by keying a figure between 1 and 23. If you push 0, no refrigeranthas been selected.

Warning: Incorrect selction of refrigerant can cause damage to the compressor.Main Function - Main Function Settings - Rfg. Type R ___

A subsequent change of refrigerant can only be performed in this way:- Select new type- The controller reports an error- Interrupt supply voltage to the controller- Wait five seconds- Reconnect supply voltage- Regulation can be started again

Other refrigerants?The function has been prepared for the definition of a refrigerant that differs from the abovementioned types. This definition can be made by keying the figure “13” plus a number ofsubsequent parameters. This setting can only be made with assistance from Danfoss.

Refrigerant


The function is used in connection with installation, service and trouble-shooting on the system.With this function, the connected functions can be checked, e.g. temperature sensors, pressuretransmitters, ON/OFF inputs and alarm function.

MeasurementsThe following functions can be read and checked here:- sensor values- voltage signals- status of the different ON/OFF input signals- status of the different ON/OFF output signals(Refer also to the menu operations)

Forced control of outputsComponents connected to the controller’s outputs can be controlled.NB! There is no monitoring when the outputs are subject to forced control.

Man. Ctrl. (access requirements)To use this service function, two settings have to be made:1. The function switch is put in pos. Service

Main Function - Main Function settings - Main switch= -1

(This will trigger an alarm message “Standby mode” to indicate that regulation hasstopped, and that all outputs are in pos. OFF).

2. “Manual control” is put in pos. ONService Mode - Manual Control of Outputs - Man. Ctrl. = ON

(Service function is activated).The individual outputs can now be controlled by force.

DO1 RelayON/OFF setting of relay outputs DO1 .... DO11If a compressor with unloaders has been connected, one of the outputs will control thecompressor while the remaining relays will control the unloaders.Service Mode - Manual Control of Outputs - DO( ) Relay OFF/ON

Alarm RelayON/OFF setting of alarm outputOFF activates the alarm (interrupted output = active alarm).Service Mode - Manual Control of Outputs - Alarm Relay: OFF/ON

AO VoltForced control of analog output “AO”Service Mode - Manual Control of Outputs - AO Volt ___

When operation with forced control is terminated (the service function is abandoned and the settingof the function switch is changed (Main Switch = 0 or 1), “Man. ctrl.” will automatically be put in pos.OFF.

Service


System measurements/data

Functions and measurements pertaining to the refrigerating system can be shown on thecontrol panel’s display or on the PC screen by system software type AKM.Displayed temperatures are indicated in °C or K, and functions with ON or OFF.

AKA 21 operationPlease refer to the menu operation - sections: controller information, compressor capacityregulation, condenser capacity regulation, etc.

A display with ***** indicates that there is a defective sensor or that a sensor has not beenmounted.

Constant updatingIf constant display of a menu is required, e.g. a temperature value, the display on the controlpanel can be locked to the menu.Procedure: Show the required menu on the display, push the ENTER key for three seconds.The function is cancelled by pushing one of the arrow keys.

PC operationPlease refer to the menu operation.

Connection of separate displayA separate display can be connected to the controller, and you can change between various typesof display by operating a switch.

The display is type AKA 14 or AKA 15 and the switch a 10-step 1 K ohm switch with 100 ohm intervalsbetween steps.The following data can be displayed at the various steps:1 (0 ohm) Cold reference2 (100 ohm) S4°C3 (200 ohm) S3°C4 (300 ohm) P0A°C5 (400 ohm) P0B / PcA°C6 (500 ohm) Status defrost7 (600 ohm) Warm reference8 (700 ohm) S7°C9 (800 ohm) Sout°C10 (900 ohm) Saux°C

If no switch is connected (open input), the display will show the actual cold reference.

If there is an error on the sensor whose value is to be shown, "AL.1" will be displayed to indicatean alarm situation.

AKC 25H7


In connection with the controller’s functions there are a number of alarms and messages whichbecome visible in case of a fault or incorrect operation.

Distinction is made between important information and not so important information. Thedegree of importance is set by the factory, but can be changed as per your wishes (see menudescription).

The importance is indicated by means of the following setting:

1. "Alarms"This is important information from the controller.- The controller’s alarm output is activated.- Information is transmitted on the DANBUSS network together with status value 1.- If a gateway type AKA 243/244 is connected and it is defined as master, its relay output

DO2 will be activated for two minutes.- Later, when the alarm is discontinued, the same information will be repeated, but this time

with status value 0.

2. "Messages"This is less important information from the controller.- The information is transmitted on the DANBUSS network together with status value 2.- Later, when the “message” is discontinued, the same information will be repeated but this

time with status value 0.

3. "Alarms"As "1", but DO2 output on a master gateway will not be activated.

0. “Suppressed information”This information stops at the controller. It is not transmitted anywhere.

List of alarm activities

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mralaoN NO FFO NO

0mralA NO FFO NO

mralaoN NO FFO NO

This is how the various messages are transmitted:Information is in principle sent twice.1) An alarm message when the error is discovered.2) A message about cancellation of the alarm situation, when the error disappears again.(In connection with a sensor alarm, there may be 10 minutes between the two messages).This procedure has a different influence on the below-mentioned systems:

Single systems (systems with control panel type AKA 21)Information can be shown on the screen, when an “E” (error) is observed.The error message cannot be removed from AKA 21, as long as the cause of the errorhas not been removed. When the cause of the error message has been removed, theerror message will remain visible in AKA 21 until it is acknowledged by pushing “Enter”.

Network (Systems with PC or AKA 243/244 with printer and control panel type AKA 21)Here the information can be transmitted to the PC or the printer. Accompanying thismessage is indication whether it is a new error or an earlier error that has been transmit-ted. On control panel type AKA 21 only “new” alarms can be seen in this situation. Olderrors that are transmitted cannot be seen.

Alarms and messages


To use this function, you have to make a setting in the controller. This setting can onlybe made from a PC.

The "Auto reset" setting is put in position "ON".The individual messages will now be sent to the printer or the PC along with a statuswhich is either 1, 2, 3 or 0.1 means that it is new and important information (information defined with setting = 1)2 means that it is new, but not quite so important information (information defined with

setting = 2)3 means that is is new and important information (information defined with setting = 3)0 means that the error has been deleted.

Who are the alarm receivers?Single systems

Control panel type AKA 21 will here be the receiver of alarms from the connected units.- Each controller is given an address, so that the unit is defined in the system. Setting of

the address is performed directly in each controller via a number of switches (cf.instructions).

Network systemsA defined PC or AKA 243/244 with printer will here be the receiver of alarms for theconnected units.- Each controller is given an address, so that the unit is defined in the system. Setting of

the address is performed via a number of switches (cf. instructions).- Each controller is given a system address. A system address consists of a network

number and an address (the address is the same as the one set in in the controller).The network number must be set via the PC.

- The addresses of the receivers of all alarms must be set on each controller. There aretwo kinds of settings which can only be carried out via the PC.• The system address of the nearest gateway type AKA 243/244 which has to

retransmit alarms and messages.• The system address of the final receiver of alarms and messages.

Alarm output on AKC 25H7The output will only be activated when the setting is [1] and [3] (see above). Activationtakes place as long as the error is active.

The output is a “change-over function” to which the following applies:No alarm: Terminals 50 and 51 are short circuited.Alarm: Terminals 51 and 52 are short circuited.


All the controllers’ inputs and outputs can be defined for compressor and condenser steps. Beyond that,most of the outputs and a few inputs may be set up for a special function which only is attached to theparticular output or input.

When the controller has to be set, you must first clarify which of the special functions are to be used. Afterthat, the remaining inputs and outputs can be used for compressor and condenser steps. We shall have alook below at an example of an arrangement of DO and DI connections:

Operating mode- The controller to control one compressor group.- S7 to be used as regulating sensor of the condenser temperature.Setting: INPUT Configuration - Application mode - Appl. Mode= 2

It is a brine-cooled condenser, and the condenser capacity must be controlled by means of a by-pass valveplus step regulation of the fans.Setting for by-pass vavlve:OUTPUT Configuration - AO Output - AO Type = 2

Relay output setupThe controller has eleven relay outputs which in the example below are used, as follows:- three for the three compressors without unloaders- three for the seven fans that are connected in binary groups, i.e. 1, 2, 4- one for the pump in the heat recovery circuit- two for the two pumps in the cold brine circuit- two for the two pumps in the warm brine circuit

Special functionsIt must first be clarified which special functions are to be used on the outputs (refer to theparagraph “Use of special functions”). Used in this example are:DO1: for Cold pump 1DO2: for Warm pump 1DO3: for Cold pump 2DO4: for Warm pump 2DO11: for Heat recovery pumpSetting:Relay output: DO1 DO2 DO3 DO4 DO11DO( ) Type: 3 3 3 3 3

CompressorsThe three compressors may now freely be defined among the remaining outputs. Outputs 5, 6 and7 are used here.The compressors must have a min. ON time of three minutes and a min. restart time of fiveminutes.Setting:Relay output: DO5 DO6 DO7DO( ) Type: 1 1 1DO( ) Dev. No: 1 2 3DO( ) Recy m: 5 5 5DO( ) ON m: 3 3 3

Example of setup ofcontroller


Exampel - continued FansThe fans may now be defined on the last three outputs.One fan is connected to DO8 => to start as step 1Two fans are connected to DO9 => to start as step 2Four fans are connected to DO10 => to start as step 3Setting:Relay output: DO8 DO9 DO10DO( ) Type: 2 2 2DO( ) Dev. No: 1 2 3

Input setupThe controller has eight digital alarm inputs which are used, as follows:

- Monitoring of the cold pumps with a flow switch- Monitoring of the warm pumps with a flow switch- Monitoring of each compressor’s safety circuit, i.e. three circuits- Monitoring of external high-pressure pressure control- Monitoring of external low-pressure pressure control- Start/stop of heat recovery

Special functionsWe must first clarify which of the inputs are provided with special functions.DI1: Cold pumpsDI2: Warm pumpsDI8: Start/Stop of heat recoveryThe time delay for the pump alarms is set at 0 seconds.Setting:Input: DI1 DI2 DI8DI( ) Type: 4 4 4DI( ) Del. s: 0 0 0

CompressorsThe three compressors may now freely be defined among the remaining inputs.Compressor 1 is connected to DI 3Compressor 2 is connected to DI 4Compressor 3 is connected to DI 5The time delay for compressor alarms is set at 120 seconds.Setting:Input: DI3 DI4 DI5DI( ) Type: 1 1 1DI( ) Dev. No: 1 2 3DI( ) Del. s: 120 120 120

Other automatic controlsThe external high and low-pressure pressure controls are defined on the last two outputs.High-pressure pressure control for DI6 with a time delay of 0 secondsLow-pressure pressure control for DI7 with a time delay of 0 secondsSetting:Input: DI6 DI7DI( ) Type: 3 3DI( ) Dev. No: 2 3DI( ) Del. s: 0 0

Electric connectionsThe connections to the inputs and outputs are, as follows:


Example - continued

Example - end


(Empty page)


Connections Survey of the controller's terminals


Brief description of the individual terminals

Inputs

Pressure transmitter inputs P0A and PcA/P0B:For one compressor group the two inputs are used for measurement of suction pressureP0A and condensing pressure PcA, respectively.For the control of two compressor groups the two inputs are used for measurement of thesuction pressure in each of the compressor groups, P0A and P0B.

Temperature sensor S3:The S3 sensor is a monitoring sensor which is normally placed in the return flow of the coldbrine.

Temperature sensor S4:The cold brine temperature is controlled by the S4 sensor. The S4 sensor will normally beplaced so that it measures the forward flow temperature of the cold brine.

Analog voltage input Ucold:Used for displacing the reference temperature for cold brine.

Temperature sensor S7:During normal operation the controller controls the warm brine temperature with the S7sensor. The S7 sensor will be placed, so that it will measure the return flow temperature ofthe warm brine.

Temperature sensor Sout:Measures the outdoor temperature at the air supply for condenser/brine cooler.

Analog voltage input Uwarm:Used for displacing the reference temperature for warm brine.

Temperature sensor Saux:During heat recovery the controller controls the forward flow temperature with the Sauxsensor. The Saux sensor must be placed, so that it measures the forward flow temperatureof the warm brine.

Main switch input:Low-voltage switch input used for start/stop of the controller.

Load shed input:Low-voltage switch input used for activation of peak load limitation.

Disp. Select input:Determines which readout is to be shown on the AKA 14 display.

Digital high-voltage input DEFR:Used for start of defrost.

Digital high-voltage alarm inputs DI1 - DI8:Eight high-voltage alarm inputs that can be defined for monitoring of compressors, fans,pumps, or other ON/OFF signals

Digital high-voltage input NIGHT:Used for start of night programme.

Outputs

Relay outputs DO1 - DO11:Eleven relay outputs, each one of which can be defined for compressor steps, condensersteps or a special function.

Relay output Alarm:Relay output activated by alarms.

DISPLAY:Output for AKA 14 / AKA 15 display.

Analog output AO:Analog 0 - 10 volt output that can be defined for high-speed regulation of fans, forcontrolling a shunt valve, or a combination of both.

Displays

LED indication:At the front there is a panel with built-in light-emitting diodes showing the status of the individualoutputs.


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Dimensions

AKC 25H7 AKC 22H


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Installation considerations Accidental damage, poor installation, or site conditions, can give rise to malfunctions of thecontrol system, and ultimately lead to a plant breakdown.

Every possible safeguard is incorporated into our products to prevent this. However, a wronginstallation, for example, could still present problems. Electronic control is no substitute fornormal, good engineering practice.

Danfoss wil not be responsible for any goods, or plant components, damaged as a result of theabove defects. It is the installer's responsibility to check the installation thoroughly, and to fit thenecessary safety devices.Particular attention is drawn to the need for a “force closing” signal to controllers in the event ofcompressor stoppage, and to the requirement for suction line accumulators.

Your local Danfoss agent will be pleased to assist with further advice, etc.

List of literature Function description AKC 25H7 (this document) ......................................................... RC.1N.P

Catalogue: Pressure transmitters, Temperature sensors ............................................ RK.00.H

Installation guide for data communication cablel ......................................................... RC.0X.A

Mounting instruction AKC 25H7 (bypacked unit) ......................................................... RI.1N.G

Montageinstruktion AKC 22H (bypacked unit) ............................................................. RI.1J.U

Menu operation via AKA 21 ......................................................................................... RC.1N.M

Menu operation via AKM.............................................................................................. RC.1N.N

Table for entry of menu settings (bypacked unit) ......................................................... RI.1N.H


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 toproducts already on order provided that such alternations can be made without subsequential changes being necessary in specifications 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.

RC

-ET

ADAP-KOOL 25 H7 Function description 06-2001.… · For users of AKM system software the complete...

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