Danfoss AK-PC 551 User guide

User Guide
Capacity Controller AK-PC 551
ADAP-KOOL® Refrigeration Control System
Introduction
Application
The controller is used for capacity regulation of compressors and condensers in small refrigeration applications. A maximum of 8 compressors and one condenser can be regulated. For example:
• One suction group + one condenser group
• Two suction groups + one shared condenser (max. 4 + 4 steps)
• One compressor group, max. 8 steps
• One condenser group, max. 8 steps
Advantages
• Energy savings via:
- Optimisation of suction pressure
- Night time increase
- Floating condensing pressure
- Load limitation
Input and output
There are a limited number of available inputs and outputs. For each signal type, though, the following can be connected:
• Analogue inputs, max. 8 pcs. Signal from pressure transmitters, temperature sensors, voltage signal, etc.
• Digital inputs, max. 8 pcs. Signal from automatic safety control, day/night signal, etc.
• Relay outputs, max. 6 pcs. Connection of compressors, condenser fans
• Solid state outputs, max. 2 pcs.
- Control of capacity valve on a Copeland digital scroll
- Control of unloader on a Copeland stream compressor.
- Control of both unloaders on a Bitzer CRII If the outputs are not used for these functions, they can be used as ordinary relay outputs
• Analogue outputs, max. 2 pcs. Speed control of compressors or condenser fans.
Operation
The daily operation can be set up directly on the controller or via an external display device. During set-up, the display images will be adjusted so that only the relevant images are opened for additional setting and end-user operation. The operation is password protected, and three levels of access can be granted. The controller contains several languages. Select the preferred language at start-up.
Data communication
The controller has built-in modbus data communication, and it can be connected to an AK-SM 800 type system device.
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Suction Group
Compressor types
The following types of compressors can be used for regulation:
• Single-step compressors (one can be speed-regulated)
• Compressor with unloaders
• Scroll compressors (one can be a digital scroll)
• Copeland Stream compressor with one unloader (4 cylinders)
• Bitzer CRII compressor with two unloaders (4-cylinders)
Capacity regulation
The cut-in capacity is controlled by signals from the connected pressure transmitter/temperature sensor and the set reference. Set a neutral zone around the reference . In the neutral zone, the regulating compressor controls the capacity so that pressure can be maintained. When it can no longer maintain the pressure within the neutral zone, the control­ler will cut out or cut in the next compressor in the sequence. When further capacity is either cut out or cut in, the capacity from the regulating compressor will be modified accordingly to maintain the pressure within the neutral zone (only where the compressor has variable capacity). – When the pressure is higher than the “reference + a half neutral
zone”, cut-in of the next compressor (arrow up) is permitted.
– When the pressure is lower than the “reference - a half neutral
zone”, cut-out of a compressor (arrow down) is permitted.
– When the pressure is within the neutral zone, the process
will continue with the currently activated compressors.
Control sensor
Normally, a suction group is controlled based on a signal from the Po pressure transmitter. If control on a brine, the S4 sensor must be the control sensor. The Po pressure transmitter must also be installed, as it is used for frost protection.
The reference
At set or variable reference can be used for regulation. For example, the variable reference can be used for a night time increase or Po optimisation. Enter a set point here so that a contribution from the Po optimisation or night time increase is added. This contribution can raise or lower the reference, as determined by the momentary cooling need. To limit the reference from values that are too high or too low, set a max. and min. limit.
Load shedding
When the load shedding function is activated, the maximum permissible compressor capacity will be limited to the set limit. In this way, the total electrical load in the store is limited. The threshold value may not be set lower than the compressor’s lowest capacity step/”Start speed”.
Po ref.
Max.
Min.
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Condenser
Fan control
The fans can be controlled incrementally using the controller’s relays, or they can be speed-controlled via the controller’s analogue output. Speed control can be via a frequency VLT-type transformer. If the fans have EC motors, the 0-10 V signal can be used directly.
Step and speed simultaneously. (Parallel signals in step with each other.) This function is primarily used to control a frequency con­verter, but if the frequency converter fails, external wiring will switch over to step control.
During night operation, the noise level of the fans can be kept down. This is done by limiting the cutin capacity. For speed control, keep the number of revolutions low. Omit step cutin for step-by-step activation.
The limitation is bypassed if safety functions Sd max. and Pc max. start to function.
Control
Regulation is carried out based on a signal from the Pc pressure transmitter or an S7 media temperature sensor. The signal is com­pared with the regulation reference.
The regulation reference can originate from one or more of the following functions:
• Fixed reference
• Variable reference, which follows the outdoor temperature. When the outdoor temperature drops, the reference will drop by a corresponding amount. This variable reference requires the installation of an Sc3 outdoor temperature sensor. The sensor must be positioned so that it registers the correct outdoor temperature. In other words, it must be shielded from direct sunlight and located near the airway of the condenser. This regulation requires setting a min. and max. reference, so that the regulation process is kept within the given limits.
• Increase the reference for heat recovery. Here the reference is raised to a fixed value when a signal is received on a DI input. The reference value can be higher than the set max. reference. When the temperature of the heat recovery has been reached and the DI signal disappears, the reference will drop once again, though it will do so over the course of a few minutes to prevent abrupt changes in the reference.
Media temperature If controlling a media temperature, the control sensor must be set to S7. This temperature sensor must be located in the desired medium. The Pc pressure transmitter must also be installed. It is used for high-pressure monitoring.
Max. ref.
Min. ref.
Ref. for heat recovery
Temperature sequence for heat recovery
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Safety functions
Min./max. suction pressure Po
The suction pressure is recorded continuously. If the measured value falls below the set minimum limit, the compressors will immediately cut out. If it exceeds the max. value, an alarm will be generated once the time delay has elapsed.
Max. condensing pressure Pc
If the condensing pressure reaches the upper permissible value, the controller will connect all condenser fans to keep the pressure down. At the same time, a portion of the compressor capacity will be disconnected. If the pressure remains near the threshold value, even more compressors will be disconnected. All compressors will be disconnected immediately if the threshold value is exceeded.
LP switch
On/off signal on a DI input If a signal is received, all compressors will immediately be stopped.
HP switch
On/off signal on a DI input If a signal is received, all compressors will immediately be stopped. Fan capacity will increase depending on how much the Pc measurement exceeds the reference.
Sensor failure
If lack of signal from one of the connected temperature sensors or pressure transmitters is registered an alarm will be given.
• In the event of a Po error, regulation will continue with a set capacity in daytime operation (e.g. 50%), and a set capacity in night operation (e.g. 25%), but with a minimum of one step.
• In the event of a Pc error, the condenser capacity that corresponds to how much compressor capacity is connected will cut in. Compressor regulation will remain normal.
• When there is an error on the Sd sensor the safety monitoring of the discharge gas temperature will be discontinued.
• When there is an error on the Ss sensor the monitoring of the superheat on the suction line will be discontinued.
• In the event of an error on the outdoor temperature sensor, Sc3, the permanent setting value will be used as a reference.
• In the event of an error on the S4 sensor, regulation will continue with the Po signal, but the reference will be lowered by 5 K.
• In the event of an error on the Saux sensor, the thermostat output will go to the rest position.
NB: A faulty sensor must be OK within 10 minutes before a sensor
alarm is cancelled.
A sensor alarm can be reset manually by pushing the "X­button" for 2 seconds when the alarm is shown in the display "Active alarms".
General DI alarms
On/off signal on a DI input The regulator contains three general alarm inputs, to which alarm text and delay times can be connected. Alarm and text will appear when the delay time has elapsed.
Min./max superheating via Ss measurement
Temperature sensor on an AI input. If superheating is higher or lower than the set limits, an alarm will be generated once the time delay has elapsed.
Max. discharge gas temperature Sd
Temperature sensor on an AI input. A signal can be received from a Pt 1000 Ohm sensor on the pressure pipe.
• Common Sd for the whole compressor group If the temperature nears the set max. temperature, the capacity of the compressor will be reduced
• Compressor Sd
if it is an Sd from a Copeland digital scroll, a Copeland stream or Bitzer CRII the capacity will be increased so that the compressor can cool down itself).
The compressors will be stopped if the temperature nears the set max. temperature value.
General thermostat
It is possible to install one general thermostat if there is a relay output and an analogue input available.
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Display overview
End-user overview
The images in this daily user interface will depend on how the set-up is made. They will illustrate what is regulated. For example: One or two suction groups, one condenser group, or a combination. See examples below:
1 suction groupe
1 condenser
group
2 suction groups
2 suction groups
and
1 condenser
group
Each of the four rows above is continued with three additional displays. The arrow in the top corner of the display shows the way to the next display in the same area of operation. By clicking the right arrow you can see these three displays:
Active alarms Cleared Alarms Information on the controller
When an alarm is sent from the controller, you must advance to this display to see the alarm text.
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Set-up overview
There are three ways in which the controller can be set up. Select the one that is easiest for you: either “Wizard”, “Quick settings” or a review of “all parameters”.
Start screen upon delivery
Operating principles
1. Select position using arrow keys
2. Select using “Enter”
3. Use the “X” to return
Hold “Enter”  down for 2 seconds to come to password entry
Select a set-up method. End by pressing “Enter”
The default password upon delivery is 300. Use the arrow keys to set the password. End by pressing “Enter”
Main Menu
The first setting is the Plant type
Wizard
Here you will be led through a series of settings, after which the controller will be ready for start. Image 1 of 28 is displayed here.
Quick
Select from the different combinations of compressors and fans here. Also see the overview on pages 18 and 19.
3CDA + 2CB + FS 2CDA + 2CB + 3F 3CSA + 2CB + FS 2CSA + 2CB + 3F 4CA + 3CB + FS 3CA + 2CB + FS 2CA + 2CB + 3F 4CDA + FS 3CDA + FS 3CDA + 3F 2CDA + 2F 4CSA + FS
Example:
3CDA + 2CB + FS =
3 Compressors, one Digital, suction group A + 2 Compressors, suction group B + one fan, Speed controlled
4CA + FS 4CA + 4F 3CSA + FS 3CA + FS 3CA + 3F None
The following options are available here:
2 Comp + 1 Cond = suction group A + B and condenser Comp. + Cond. = suction group A and condenser Condenser = condenser only
When the Plant type has been selected, it will al-
Compressor = suction group A only None
low several settings to be made. For example:
Continue to the next menus. All settings are explained on the pages that follow.
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Menu
Start/stop
Plant type
Suction A
Main switch Main switch
Start and stop regulating here. The configuration settings will require that regulating is stopped. If you try to enter a configuration setting when regulating has started, the controller will ask if regulating should be stopped. When all settings have been made and the main switch is set to “ON”, the controller will enable the display of the various measurements. Regulation will start. (If an external main switch has been defined, it must also be “ON” before regulating starts.)
Extern Main swich External main switch
It is possible to connect an external switch which can be used to start and stop regulating. Both the internal and external main switch must be ON before regulating starts. An external main switch can be defined in the menu “Plant type” - “Main switch via DI”.
Select Plant type Plant settings:
The following must be regulated:
• Compressor group
• Condenser group
• One compressor group (A) + One condenser group
• Two compressor groups (A) and (B) + One condenser group
Refrigerant type Refrigerant setting
Before refrigeration is started, the refrigerant must be defined. You may choose between the following refrigerants: R12, R22, R134a, R502, R717, R13, R13b1, R23, R500, R503, R114, R142b, user defined, R32, R227, R401A, R507, R402A, R404A, R407C, R407A, R407B, R410A, R170, R290, R600, R600a, R744, R1270, R417A, R422A, R413A, R422D, R427A, R438A, R513A (XP10), R407F,
R1234ze, R1234yf, R448A, R449A, R452A.
Warning: Wrong selection of refrigerant may cause damage to the compressor. Other refrigerants: Here Setting "user defined" is selected and then three factors - fac1, fac2 and fac3 and temperature glide (if necessary).
Unit of setpoints Device for controlling compressor and condenser
Select pressure or saturation temperature. (Can be set during initial set-up and must not be subsequently changed.)
Night signal via DI Night time operation via DI signal
Define an external switch here, so that the regulation reference can be raised and lowered externally.
1. Set the function to “Yes”
2. Go to I/O configuration and select an available digital input. Set this input to “Night condition”
3. Next, define whether the function is to be active when the signal is ON, or when it is OFF.
Main Switch via DI Main switch via DI
Define an external main switch here, so that regulation can be started and stopped externally.
1. Set the function to “Yes”
2. Go to I/O configuration and select an available digital input. Set this input to “Main switch”
3. Next, define whether the function is to be active when the signal is ON, or when it is OFF.
Mains frequency Frequency
Set the net frequency
Alarm output Alarm relay
Define an alarm relay here that will be activated in the event of an alarm.
1. Select the alarm priority that will activate the relay
• No relay
• Critical alarm
• Severe alarm
• All alarms
2. Go to I/O configuration and select an available digital output. Set this output to “Alarm”
3. Next, define whether the relay will be active (pulled) when the alarm is ON, or when it is
OFF.
Alarm buzzer Alarm sound
Here the sound generator can be defined to emit a sound in the event of an alarm. Select which alarm priority will activate the sound generator:
• No buzzer
• Critical alarm
• Severe alarm
• All alarms (In the event of an alarm, the sound generator can be stopped by moving across the active alarm screen; see page 6)
Control status Regulation status
SW: 1.6x
On / Off
Fac: None
Fac: None
Temp. / press Fac: Saturated
DI-demand
No / Yes Fac: No
DI-demand
No / Yes Fac: No
50 Hz / 60 Hz Fac: 50 Hz
DO-demand
Fac: No relay
Fac: No buzzer
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