Controller Functionality; Functions; Liquid Injection By Use Of Akv; Liquid Injection By Use Of Stepper Valve - Danfoss AK-CC55 User Manual

AK-CC55 Single Coil and Single Coil UI

Controller functionality

Functions

• Day/night thermostat with ON/OFF or modulating principle
• Product sensor S6 with separate alarm limits
• Switch between thermostat settings via digital input
• Adaptive control of superheat
• Adaptive defrosting based on diagnostics
• Start of defrost via schedule, digital input, network or setting display
• Natural, electric or hot gas defrost
• Stop of defrost on time and/or temperature
• Coordination of defrosting among several controllers in a line-up
• Pulsing or ECO control of fans when thermostat is satisfied
• Appliance cleaning function for documentation of HACCP procedure
• Rail heat control via day/night load or dewpoint
• Humidity control in cold storage rooms
• Door function
• Control of two compressors
• Control of night blinds
• Light control
• Heat thermostat
• High accuracy inputs will guarantee a better measuring accuracy than stated in the standard EN ISO 23953-2
without subsequent calibration (Pt 1000 ohm sensor)
• Integrated MODBUS communication with the option of mounting a LonWorks communication card

Liquid injection by use of AKV

Liquid injection in the evaporator is controlled by an electronic injection valve of the type AKV. The valve operates
as both expansion valve and solenoid valve. The controller opens and closes the valve based on sensor readings.
The function contains an adaptive algorithm which independently adjusts the valve's opening so that the
evaporator constantly supplies optimum amount of refrigerant.

Liquid injection by use of stepper valve

Instead of AKV, an external stepper driver can be connected to AO1 (0 – 10 V) to drive a stepper valve. DO1 (AKV
output) is then configured to close a liquid line solenoid valve (LLSV) when a valve output is 0%. The LLSV is also
closed at power failure.
Superheat is measured via:
Pressure sensor Pe and temperature sensor S2. By using a pressure sensor, and temperature sensor a correct
measurement of superheat is achieved under all conditions which ensures a very robust and precise control. The
signal from one pressure transmitter can be shared by max. 10 controllers, but only if there is no significant pressure
difference between the evaporators in question.
There are two parallel settings for superheat:
• Dry expansion, which does not allow liquid flow on the outlet of the evaporator.
• Adaptive liquid control in transcritical CO
controller receives an on/off signal from (for example) a suction accumulator in the suction line. A level switch in
the tank will register when the liquid level exceeds the max. level. When this happens, the controller will switch to
dry expansion, and then back to liquid control when the liquid level has dropped. The function is defined in
setting o02, o37 or o84.
The function can also be activated via data communication from a system unit. If the adaptive liquid control signal is
lost, the controller will automatically switch back to dry expansion.
© Danfoss | Climate Solutions | 2021.02
systems, which allows liquid flow. This type of control requires that the
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