Function description ADAP-KOOL. Controller for capacity regulation of brine installation AKC 25H7

Transcription

1 Function description ADAP-KOOL Controller for capacity regulation of brine installation AKC 25H7 RC.1N.P1.02 RC.1N.P

2 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 Hourmeter Forced control of compressor capacity Other functions belonging to the compressor operation13 Peak load limitation Accumulation of ice Compressor control, - but not condenser control Injection signal Start-up procedure Defrost Pump control Cold side Warm side Control of warm brine temperature General description Control of condenser temperature Control of heat recovery Limitations Examples of setup of references and limitations Capacity regulation of condenser Choice of system structure Regulation Neutral zone Fan definition Time delays for cutins and cutouts How to prevent that fans get stuck Signal from the fans safety controls Hourmeter Forced control of condenser capacity Condenser control, but not compressor control Use of special functions Thermostat function Monitoring Monitoring of maximum discharge pressure Monitoring of minimum suction pressure Monitoring of temperatures Monitoring of ON/OFF functions Sensor failure General information Supply voltage Function switch (Main Switch) Clock function Access codes Refrigerant Service Measurements Forced control of outputs System measurements/data AKA 21 operation PC operation Forced control of outputs Alarms and messages The importance is indicated by means of the follow This is how the various messages are transmitted: Who are the alarm receivers? Example of setup of controller Connections Survey of the controller's terminals Brief description of the individual terminals Technical data Dimensions Ordering Installation considerations List of literature Validity This function description is make out in June 2001 and applies to AKC 25H7 with code numbers 084B2022 and 084B Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

3 Introduction Application AKC 25H7 is a complete brine cooler control unit that has been developed for indirect refrigerating 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 the required 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. AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/2001 3

4 Systeminformation Controller type AKC 25H7 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 25H7. (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). Operation 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). Language 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 Swedish. 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 6: Swedish Activate the selected language by pushing "Enter" and then push "Clear". 4 Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

5 Application 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 brine temperature S7. Pc used for monitoring (Appl. Mode = 2). Used where one or more condensers are brine-cooled and connected to the same brine circuit. 3 Control of two compressor groups according to S4 and two condensers based on brine temperature 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 mentioned earlier in the introduction. Setting: INPUT Configuration - Application mode - Appl. Mode Hint! The controller can also be used in systems with direct expansion and application modes 1 and 2. The heat exchanger and S4 are not mounted, so regulation will take place based on P0. (S4 must not be used and the alarm destination for S4 must be set to 0). AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/2001 5

6 Control of cold brine temperature General description AKC 25H7 controls the cut-in compressor capacity, so that the temperature at the sensor (S4 or P0) corresponds to the reference temperature. The actual regulation of the compressors takes place by means of a neutral zone controller which adjusts the cut-in compressor capacity to the actual load of the connected cooling/freezing points. AKC 25H7 can control and monitor one or two compressor groups with max. 11 compressor steps 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 reference Regulation of the cold brine temperature (S4 or P0 in connection with DX application) takes place on the basis of a reference value comprising a set value plus a number of functions that will be added to this value. Displacement functions are used for adjusting the reference temperature 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 of time, 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 be put in. Below we give you a description of the individual contributions and the limitation function: Set value Setting of setpoint value for S4 (P0) temperature: Setting: Compressor Capacity Ctrl. - Cold Temp. Control - Cold SP Contribution from day/night function With this function the reference can be displaced by up to 25 K in positive or negative direction. When a night lid is placed on the appliances, the load will drop considerably, and the 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 be lowered 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 the night 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. 6 Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

7 The function can be activated in two ways: 1) Signal on NIGHT input When 230 V is fed to this input, the night setback function will be activated. 2) 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. 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. Setting: Day/Night Clock - Day/Night Setting - Mo day h (+more) AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/2001 7

8 Contribution from an external voltage signal With a 0-10 V d.c. voltage signal on the U COLD input the reference can be displaced by up to 50 K in positive or negative direction. The signal may be supplied from a transmitter or another general control giving a signal on the 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% relative humidity 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 reference should 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 signal With this function it is possible to displace the reference on the basis of a measured temperature S3. The sensor can for instance be placed in the brine s return flow temperature or on the business premises. A reference is obtained in this way which should be 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 = 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). 8 Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

9 Limitation of reference To prevent that the sum of the contributions from day/night, voltage signal and temperature signal will result in a too big displacement, a permissible working range must be stated for the 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 compressor The 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 the S4 sensor and based on whether the temperature is rising or falling. Or with the P0 pressure transmitter if S4 has not been mounted, for instance in connection with control of a system by means 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 set Time delay in +Zon e and - Zone band is set Time delay in ++Zone and Zone band is set Compressor Capaciy Ctrl. - Compressor Step Control - NZ, etc. Compressor definition All the relay outputs can be used for compressors and fans, but you may also select a third function which is specific for the given output. It is necessary, for example, to clarify which of these special functions are to be used before outputs for compressors and fans can be selected. Reference is made to the paragraph about the use of special functions. The controller can control one or two compressor groups with up to 11 compressor steps distributed on max. eight compressors. When relay outputs for compressors are fitted, it must be defined by means of the setting: DO Type = 1 (fan defined with 2 and special functions with 3 ). AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/2001 9

10 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 must be defined with the same number. The controller knows in this way which step belongs to a given compressor. Based on the same settings the controller will then use the relay output with the 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 be considered. - 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.4 DO4 Type = 1 (1 = compressor) DO4 Dev. No=2 (compressor B1, step 2) DO Relay No.5 DO5 Type = 1 (1 = compressor) DO5 Dev. No=3 (compressor A2, step 1) DO Relay No.6 DO6 Type = 1 (1 = compressor) DO6 Dev. No=4 (compressor B2, step 1) Time delay for cutins and cutouts To protect the compressor motor against frequent cutins and cutouts two time delays can be put in. - 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 controlling the 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 10 Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

11 Sequence for cutin and cutout of capacity The sequence for cutin and cutout of compressor capacity can be defined in two ways. Either with a fixed sequence or automatic equalisation of the operating time between the compressors. 1) Sequential cutin and cutout (Step Mode = 1) Cutin Cutin 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 compressor with the subsequent number. If compressors with several steps are included, all steps of one compressor will be cut in before the next compressor is started. Cut in Cut out If the controller has been set to control two compressor groups, cutin of the compressor capacity will take place alternately between groups A and B, so that there will be an even distribution of capacity between the two groups. Within the individual group cutin of compressor capacity will still take place in the sequence defined for the compressors. Cut in Cut out Cutout The 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. This function sees to it that the last cut-in compressor will not stop until the previous compressor has cut out one unloader. - Compressor groups If two compressor groups are used, cutout of the steps will take place alternately between group A and group B. Within the individual group cutout of compressor capacity will follow the rules described above. 2) Automatic equalisation (Step mode = 2): With this setting the controller will perform an automatic operating time equalisation between the 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. AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/

12 - For compressors with several steps there will be no reorganisation of the steps, as the case is for sequential coupling. The result is that there will only be one compressor at a time with cut-out unloaders. - If two compressor groups are used, equalisation of the operating time will take place within each group, but not between the groups. Settings: Compressor Capacity Ctrl. - Compresssor Step Control - Step Mode Signal from the compressor's safety controls All digital alarm inputs (DI1 - DI8) can be used for monitoring of compressors and fans, or for the individual inputs a third function. This third function is specific for a given input. In other words, 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 the compressor in question and give alarm (for the sake of safety the safety circuit must stop the compressor without the assistance of AKC 25H7). Regulation continues for the remaining compressors. When a digital alarm input is mounted, the purpose must first be defined. When a compressor has 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 cut out and until AKC 25H7 reacts to the alarm. Settings: INPUTConfiguration - Setting of Alarm input DI( )Type, DI( )Dev.No, DI( )Del. s etc. Hourmeter An hourmeter is attached to all relay outputs. The hourmeter registers the time the output in question has been activated since it was last zeroset. The hourmeter range is from 0 to 30,000 hours. Readout/Setting: OUTPUT Configuration - DO Relay No.( ) - DO( ) Time 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. Setting: Compressor Capacity Ctrl. - Compressor Step Control - Man.Cap, Man Cap. % 12 Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

13 Other functions belonging to the compressor operation Peak load limitation This function may limit the energy consumption during certain periods where the cut-in capacity must be kept below a certain level. The level is set as a per cent of the total compressor capacity. 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 actual energy consumption. Setting: Compressor Capacity Ctrl. - Compressor Step Control - LoadShed. % Accumulation of ice The analog AO output will provide a 0 to 10 V signal, if the output is not used for controlling the condenser capacity. The signal will then represent the cut-in compressor capacity (0 to 100%). The signal may be used by other automatic controls, e.g. for controlling the accumulation of ice. In periods where the price of electricity is low and the compressor capacity not fully utilised, for example, other automatic controls may allow accumulation of ice. Compressor control, - but not condenser control The controller is normally used for controlling both the compressor and the condenser. However, if the controller is only used for controlling the compressor, a lack of signal to pressure transmitter input PcA may produce the result that the alarm will sound. But the alarm function may be cancelled by setting the alarm destination for PcA/P0B and HP Max at 0. Please refer 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 signal Injection into the evaporator must be synchronised with the compressor operation. The injection must start at the same time as the first compressor starts, and it must stop at the same time as the 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 activating the 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 may be 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 switch All auxiliary switches from the same compressor group must be connected in parallel. AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/

14 A voltage signal is via the in-parallel connected auxiliary switches connected to the solenoid valve 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 procedure The controller contains functions ensuring a correct interaction between pumps, compressors and injection during start-up. Pumps During 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 required before the first compressor can start. The time can only be changed via software type AKM. Capacity limitation If too much compressor capacity is cut in during the start-up phase, the compressors will drop out on low pressure. To prevent this, a time delay of 120 seconds has been placed between the first and the subsequent capacity step. The time can only be changed via software type AKM. Injection The signals from DO6 and DO7 will not release the injection until the suction pressure has dropped to a value which will ensure that the compressors are not overloaded. The injection will only be released at a suction pressure corresponding to a value of 5 K above the reference value for the cold brine temperature. The value can only be changed via software type AKM. Defrost The controller can carry out central defrost of the whole cold brine circuit. When a defrost is initiated, 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 be activated during the defrost: Define relay output DO8 to follow the defrost function by means of the setting: Type = Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

15 Defrost start Defrost can be started in three ways: 1. Manual defrost Manual defrost is started via control panel AKA 21 or a PC. The setting automatically returns to OFF when the defrost has been completed. Start with the setting: Man.Def. = ON 2. Signal on input DEFR When 230 V a.c. is received on input DEFR, the defrost will start. The signal must be a pulse signal of at least 2 sec. duration. If the external signal remains active 30 minutes after the resumption of refrigeration, there will be an alarm. The alarm is cancelled, when the defrost signal is removed. 3. Internal time schedule Defrost is started via a weekly programme which has been set in the controller. The times relate 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 Def 2 Sc1 etc. Hour Min Hour Min Schedule 2 Schedule 3 No. Per Day. Def 1 Sc2 etc. No. Per Day. Def 1 Sc3 etc. Hour Min Hour Min Def. Schedule Day selection Mon Sched. 1/2/3 Tue Sched. 1/2/3 etc. Defrost stop You 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 the set 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 the defrost is stopped, the alarm message Defrost time exceeded will appear. The alarm will stop 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 time A fixed defrost time is set here. When this period of time has elapsed, the defrost will stop and cooling will be resumed. Settings: Defrost Control -Defrost stop Method Temp/Time (2 = stop on time) MaxDefTime AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/

16 Pump control Cold side The controller can control and monitor one or two pumps circulating the cold brine. If two pumps are used and equalisation of operating time is selected, the controller can also alternate between 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 pump It 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 stopped 1: pump 1 put into operation 2: pump 2 put into operation 3: both pumps put into operation 4: automatic change-over between pumps allowed Setting: Pump Control - Pump Cold Brine - CPump Ctrl Automatic change-over between the pumps (only when setting = 4). With this setting the operating times of the two pumps will automatically be equalised. Set the required working period for the pump. When this working period has elapsed, the other pump will be started. (At start-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 active pump is stopped. Set the required overlap time. Setting: Pump Control - Pump Cold Brine - CPumpDel.s Pump Control - Pump Cycle - PumpCycl.h Monitoring of pumps General If the controller is to monitor the pump operation, the controller s digital alarm input DI1 must be 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. If the 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 the period of time between the moment the input loses the signal and the controller s alarm. Especially where there is equalisation of operating time when the pumps are operating with automatic equalisation of operating time, the controller will carry out a change-over between pumps when the flow is insufficient (the change of pump will however not take place until the time delay for the alarm has expired). Depending on whether 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 fault- less pump now operating will keep 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 16 Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

17 situation (alarm is cancelled). If the faulty pump has not been repaired, another alarm will be released, and there will be another change-over to the faultless pump. This process will 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 give an alarm for the other pump. At the same time, both pump outputs are activated in an attempt to create so much flow that the alarm situation will be cancelled. The controller will 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 both pumps. Please read the section named Alarms and Messages. Warm side The controller can control and monitor one or two pumps circulating the warm brine. The control and monitoring is in principle the same as mentioned in the section about cold brine, but there are 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 AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/

18 Control of warm brine temperature General description AKC 25H7 can control air-cooled as well as brine-cooled condensers. Capacity control can take place with various functions, e.g. step coupling or speed control of fans and control of a by-pass valve. During normal operation the cut-in condenser capacity will then control the cut-in condenser capacity, so that the condensing temperature measured with S7 or with Pc sensor will correspond to the reference temperature. During heat recovery the cut-in condenser capacity will then control the forward flow temperature (Saux), so that the warm brine is adjusted to the actual load in the heat recovery circuit. The condenser pressure, expressed either by Pc or S7, is monitored constantly, and it is ensured 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 Reference The condenser temperature is controlled by the S7 or Pc sensor, depending on the application chosen. Control takes place according to a reference value consisting of a set value (setpoint) and a variable 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 last link 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 a minimum will always have a fixed differential above the outdoor temperature (measured with Sout). (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 reference Setting: CondenserCapacity Ctrl. - Warm Temp. control - Warm SP C 18 Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

19 Contribution from an external voltage signal With a 0-10 V d.c. voltage signal on input U WARM the reference can be displaced by up to 50 K in positive or negative direction. The signal can be supplied from a transmitter or 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. limits can 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 temperature It is possible to have the condenser reference follow the outdoor temperature, so that it 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 the reference value for the condenser temperature, the reference value will be raised by the set value. The value could for instance be the temperature differential according to 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 the range 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. AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/

20 Control of heat recovery During normal operation the condenser temperature is controlled according to S7 or Pc. When heat recovery is activated, the reference is changed, and the controller will now control on the basis of the Saux sensor. Activation of heat recovery The heat recovery function must be activated by a signal on input DI8 (230 V a.c.). The DI8 input must be defined, so that it can be used for the heat recovery function. Setting: INPUT Configuration - Setting of Alarm input DI 8 Type 4 (4 = heat recovery) Definition of output Relay output DO11 can be defined to follow the heat recovery function. The output can for instance 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) Reference When 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 a period 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 the condenser 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 signal With a voltage signal of 0-10 V d.c. on the Uwarm input the reference can be displaced by up to 50 K in positive or negative direction. The signal will typically come from an overriding control unit. Please note: it is the same voltage signal which is part of the reference for the condenser temperature (the only difference being the constant K4). The contribution 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 Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

21 - Contribution from outdoor temperature The function is used for displacing the brine s forward flow temperature (Saux) in relation to the outdoor temperature. As the need for heat recovery normally depends on the outdoor temperature, the function will adjust the heat recovery temperature to the actual load. 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. Limitations When the heat recovery function is activated, the controller, as mentioned, will control the forward flow temperature of the warm brine (Saux), but the controller also still controls the condenser temperature (S7 or Pc). So if one of the set nax./min. values is exceeded, the following will happen: Pc/S7 max. limitation The controller will control the condenser temperature (Pc/S7) with a reference corresponding to the 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. limitation The controller cuts out the heat recovery output DO11 if the condenser temperature drops below 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 the limitation 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 outdoor temperature 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. / Setting Heat 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. AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/

22 - 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 x Uwarm - The condenser temperature is furthermore limited between 10 and 35 C. Warm Ref C Heat Ref Pc/S7 Max. Warm SP Pc/S7 Min. 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 C For 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 be below 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 (Sout - 18 C) - The condenser temperature is furthermore limited between 10 and 40 C. Warm Ref C Heat Ref C Pc/S7Max. Warm SP Pc/S7Min. 22 Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

23 Capacity regulation of condenser Choice of system structure Regulation of the condenser capacity can be accomplished in various ways. The type of regulation 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). Capacity The condenser capacity is controlled exclusively by the fans defined on the DO outputs (the analog output AO will produce a voltage between 0 and 10V corresponding to the cut-in capacity). 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 Capacity 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 Capacity Heat recovery By-pass Closed Open PI-control of by-pass valve NZ control of fans The lower end of the capacity regulation is handled by the by-pass valve, and step regulation 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. AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/

24 3. The capacity is controlled by a combination of by-pass valve action and speed regulation of fans. (AO Type = 3) Capacity Heat recovery By-pass Closed Open PI-control of by-pass valve PI-control of fans The 0-10 V signal from analog output AO is used here both by the by-pass valve and the speed regulation for the fans: 0-5 V is used for the by-pass valve 5-10 V is used for the speed regulation The lower end of the capacity regulation is handled by the by-pass valve, and speed regulation 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 corresponds to 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 Regulation The 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 speed regulation, the controller will function as a PI regulator. Here it will constantly try to adjust the capacity 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 controller will 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. 24 Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

25 A function has been incorporated in the controller which adjusts the time delays for cutins and cutouts of fans. The time delays depend among other things on the deviation between the actual temperature and the required temperature. If the deviation between the actual temperature and the reference is big, the controller will operate with short time delays. If the deviation 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 zone The width of the neutral zone will affect the time delays for cutin and cutout of fans. The width of the neutral zone should therefore not be set at a too high or too low value. Normally a neutral zone width of 2 to 5 K will be appropriate. Setting: Condenser capacity Ctrl. - Condenser Step Control - NZ K Fan definition All the relay outputs can be used for compressors and fans, but you may also select a third function which is specific for the given output. It is therefore necessary to clarify which of these special functions are to be used before outputs for compressors and condensers are selected. Please read the paragraph about the use 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 with the 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 out first. 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 DO Relay No. 9 DO6 Type = 2 (2 = fan) DO6 Dev. No. = 1 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 be an advantage to divide the fans into groups. In this way we obtain a better regulation of the capacity. E.g.: 1st step: 2nd step: 3rd step: 4th step: 5th step: 1 fan 2 fans 4 fans 8 fans etc. Time delays for cutins and cutouts Values for minimum ON and OFF times for fans cannot be defined. In the controller greater importance has been attached to the accuracy of the regulation than to the start/stop sequence for the fans. How to prevent that fans get stuck If a fan is never started for a long period of time, there is a risk that it will get stuck. To prevent this, the controller contains a function that will check once a day (around noon) whether the fan outputs have been activated during the past 24 hours. The fan outputs which have not been activated will then be activated one by one (for five seconds each). AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/

26 Signal from the fans safety controls All digital alarm inputs (DI1 - DI8) can be used for monitoring of fans or compressors, but for a few inputs there can be a third function. The third function is specific for a given input. This means that the use of these specific functions has to be clarified before inputs for fans (and compressors) 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. The signal 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 the controller). 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 be monitored, 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 is cut out and until AKC 25H7 gives alarm. Settings: INPUT Configuration - Setting of Alarmi input DI ( )Type, DI( )Dev.No, DI( ) Del. s Hourmeter An hourmeter is attached to all relay outputs. The hourmeter registers the time the output in question 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 capacity There can be forced control of the capacity where the normal regulation and safety function are disregarded. 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 control The controller is normally used for controlling both compressors and condensers. If the controller is only used for controlling condensers, a lack of signal on the pressure transmitter side POA may produce the result that the alarm is sounded. To avoid this, the alarm destinations for the PO 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) 26 Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

27 Use of special functions All relay outputs DO1 to DO11 and digital alarm inputs DI1 to DI8 can be used for compressors and fans. But beyond that there are special functions belonging to a certain output/input. The use of these special functions must be clarified before outputs and inputs for compressors and fans are selected. In the survey below the special functions are shown in the last two columns: Output Type 1 Type 2 Type 3 Type 4 DO1: Comp. Fan Cold pump 1 DO2: Comp. Fan Warm pump 1 DO3: Comp. Fan Cold pump 2 DO4: Comp. Fan Warm pump 2 DO5: Comp. Fan DO6: Comp. Fan Injection function B DO7: Comp. Fan Injection function A DO8: Comp. Fan Defrost DO9: Comp. Fan Night setback DO10: Comp. Fan Thermostat DO11: Comp. Fan Heat recovery DI1: Comp. Fan Other monitoring Cold pump 1 and 2 DI2: Comp. Fan Other monitoring Warm pump 1 and 2 DI3: Comp. Fan Other monitoring DI4: Comp. Fan Other monitoring DI5: Comp. Fan Other monitoring DI6: Comp. Fan Other monitoring DI7: Comp. Fan Other monitoring DI8: Comp. Fan Other monitoring Heat recovery on/off. Thermostat function The controller contains a separate thermostat function which may be used, as required. It is for example capable of starting a fan in the compressor room, if the temperature exceeds a set value. It is possible to select thermostat sensor and cutin and cutout limits, but it is only output DO10 that can be defined to follow the thermostat function s ON/OFF performance. The sensor is defined with settings 1 to 7: 1) PoA 2) PcA/PoB 3) S3 4) S4 5) S7 6) Sout 7) Saux Setting: 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 DO10 Type Thermostat settings: - Thermostat's cutin value in C - Thermostat's cutour value in C Settings: Thermostat / Temp. Alarms - Thermostat - ThCutin C, ThCutout C AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/

28 Monitoring Monitoring of maximum discharge pressure (safety function) The function cuts in condenser steps and gradually cuts out compressor steps, if the condensing pressure exceeds the permitted value. The cut out limit can be defined in the range between -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 condenser capacity is cut in at the same time as half of the compressor capacity is cut out. The alarm function is activated. There is now a 30 second wait and if the pressure is still in the critical range, half of the actual compressor steps are again cut out. This continues until the pressure has dropped below the critical limit or all compressor steps have been cut out. HP Max. Alarm Cond. Cap. Comp. Cap. 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 complied with: - 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 28 Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

29 Monitoring of minimum suction pressure (safety function) The function immediately cuts out all compressor steps if the suction pressure becomes lower than 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 other compressor group). LP Min. Alarm Comp. 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 complied with: - 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 restart The time delay for restart is common to the two safety functions. HP Max LP Min 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 AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/

30 Monitoring of temperatures The function will sound the alarm if the set temperature limits are exceeded on the following sensors: 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 has expired. Three time delays have to be set (in minutes): - For too high temperature: High1Del.m: Time delay for restart and after defrost The time delay will apply until the actual temperature has dropped below the 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 High1Del.m High2Del.m Low Del.m High / Low Alarm limit for high temperature and low temperature S: Alarm ceases Curve 1: Curve 2: Curve 3: Cooling stage (1): time delay "High1Del.m" has been exceeded. Alarm becomes active. Normal regulation where the temperature becomes too high (2): time delay "High2Del.m" has been exceeded. Alarm becomes active. Temperature becomes too low (3): Time delay "Low Del.m" has been exceeded. Alarm becomes active. 30 Function description RC.1N.P2.02 Danfoss 06/2001 AKC 25H7

31 Monitoring of ON/OFF functions The controller is provided with eight digital alarm inputs DI1 - DI8. Some of the inputs are used for compressors, condenser steps, pumps, etc. The remaining inputs may be used for other purposes to the extent required. Various elements in the compressor s safety circuit A simple monitoring of compressors, condensers and pumps has been described in the respective paragraphs, but the monitoring of a compressor can be extended from being a simple monitoring process to differentiated monitoring of several elements of the safety circuit. This will require that the controller is linked up with an alarm module type AKC 22H. This alarm module will then receive signals from the different elements of the safety circuit, and in this way deliver an accurate report as 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 safety controls. All alarm modules are double, i.e. one module can monitor two safety circuits. Each circuit is connected to a DI input on AKC 25H7. AKC 25H7 Function description RC.1N.P2.02 Danfoss 06/