Liquid Injection; Superheat Is Measured Via; Temperature Control; Thermostatic Expansion Valve Control - Danfoss AK-CC55 User Manual

User Guide | Controller for appliance control, AK-CC55

Functions

Liquid injection

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.

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 several
controllers, but only if there is no significant pressure difference
between the evaporators in question.
There are two parallel settings for superheat:
1. Dry expansion, which does not allow liquid flow on the outlet of
the evaporator.
2. Adaptive liquid control, which allows liquid flow. This type of
control requires that the 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.

Thermostatic expansion valve control

In the compact version the refrigeration (injection) can be
controlled either by starting/stopping a compressor or by
opening/closing a solenoid valve in the liquid line.
Modulating temperature regulation is used in brine systems.

Temperature control

The temperature in the appliance is registered by one or two
temperature sensors which are located in the return air before the
evaporator (S3) or after the evaporator (S4) respectively. A setting
for the thermostat, night thermostat, alarm thermostat and display
reading determines how much the two sensor values should
influence each individual function, e.g. 50% of S4 will produce an
equal value from both sensors.
The actual temperature control can take place in two ways: as an
ordinary ON/OFF regulation with a differential, or as a modulating
control where the temperature variation will not be nearly as
great as in ON/OFF control. There is, however, a limit to the use of
a modulating control as it can only be used in remote cabinets.
In applications with one evaporator and one compressor the
thermostat function with ON/OFF control should be selected.
In remote cabinets, the thermostat function may either be se-
lected for ON/OFF control or modulating control.
For the Multi Coil version, regulation can also be performed using
a shared on/off thermostat for all sections. The thermostat sensor
must be either: S4A, average of all S4 sensors or the S4 sensor for
which the highest temperature is recorded.
© Danfoss | DCS (vt) | 2019.09
Warning
Accidental actuation may allow liquid throughput to the compressor.
It is the installer's responsibility to ensure that signal loss to the controller will
not result in liquid throughput to the compressor.
Danfoss accepts no responsibility for damage resulting from inadequate
installation.
BC308437742037en-000101 | 39