Danfoss EKC 326A User guide

User Guide

Controller to regulate

CO2 gas pressure

EKC 326A

ADAP-KOOL® Refrigeration control systems

Introduction
Application
The controller can be used in systems with transcritical and sub-
critical cooling control systems where CO2 is used as a refrigerant.
The controller regulates the pressure in the gas cooler (condens-
er) so that the system achieves the optimal COP.
The controller covers the following:
• Transcritical CO2 refrigeration systems (booster, cascade, high
pressure)
• Transcritical CO2 heat pump systems
• Transcritical CO2 refrigeration systems with heat recovery
• Transcritical CO2 chiller systems
• Extra capacity in warm periods. An improvement in the system’s
cooling performance can be achieved by displacement of the
set point (“extra compressor")
Advantages
• Maximum COP
The controller guarantees the system’s maximum performance
by maintaining the optimal pressure in the gas cooler when
regulation takes place in the transcritical range.
• The controller will always optimise to a subcritical state.
• Regulating the receiver pressure based on the receiver pressure
reading
• Heat recovery with adjustable reference pressure, 0-10 V
• Optimum heat pump operation
System
The pressure in the gas cooler is controlled by the valve. Regula-
tion must have inputs from both a pressure transmitter PGC and
a temperature sensor SGC. Both must be fitted in the outlet im-
mediately after the gas cooler.
The valve is an ICMTS valve, which has been specially developed
for the pressure conditions that exist in a transcritical CO2 system.
The motor section of the valve is an ICAD actuator and is control-
led by a 0-10 V signal from the controller.
If it is necessary to maintain a constant receiver pressure, a valve
(ETS, CCM or CCMT) and pressure transmitter (Prec) can be in-
stalled. The gas from the receiver bypasses to the inlet side of the
high pressure compressor.
Functions
Maximum COP control
The controller maintains optimum pressure in the transcritical
range based on a pressure and temperature reading.
The reference line is defined with a point at 100 bar. The desired
temperature can be set here.
Subcooling
d T subcooling can be used in the subcritical range.
Contents					Menu survey	10
Introduction........................................................................................................				2	Menu survey	10
Examples..............................................................................................................				4	Connections......................................................................................................	11
Survey of functions..........................................................................................				6	Data......................................................................................................................	13
Operation...........................................................................................................				10	Ordering.............................................................................................................	13
					Appendix............................................................................................................	14
2	Manual	RS8FM602	©	Danfoss	02-2016	EKC 326A

Receiver control
The receiver pressure can be controlled so that it is kept at a set
reference point. This control requires the installation of an ETS
valve a (CCM valve) and a pressure transmitter.
If only monitoring and not control is required, the valve should
not be installed. Install the pressure transmitter only.
Ensuring that the receiver pressure is not too low
A limit value can be set, and if the pressure falls below this value,
the ICMTS valve will be opened. The valve will then open gradually
through the associated P band. Open to the value "n32" ( Vhp OD
Max).
Protecting against high receiver pressure
A limit value can be set, and if the pressure rises beyond this value,
the ICMTS valve will be closed. The valve will then close gradually
through the associated P band.
Extra refrigeration capacity (“extra compressor”)
This function improves the system’s refrigeration capacity by
increasing the reference pressure in the gas cooler with a offset
value.
It is activated via a switch function.
Heat recovery or heat pump
This function will increase the gas pressure to a set value. This
value will be equivalent to a specific temperature.
The value can either be fixed or can vary in accordance with an
input signal of 0-10 V as follows:
A signal of 1.5 V or above can activate the function and increase
the reference to Pgc HR Min.
If a variable reference is required, then a signal between 2-10 V
can be connected. The signal will increase the reference further.
This function works both in subcritical and transcritical ranges.
Output signal
The controller has a voltage output on 0-10 V. The signal is used to
control the ICMTS valve via the ICAD actuator.
Valves opening degree
The opening degree of both ICMTS and ETS valves (CCM valve)
can be narrowed if necessary.
PC-operation
The controller can be provided with data communication so that it
can be connected to other products in the range of ADAP-KOOL®
refrigeration controls. In this way operation, monitoring and data
collection can be performed from one PC – either on the spot or in
a service company.
Temperature reading
The temperature by the gas cooler must be measured using a Pt
1000 ohm sensor type AKS 21.
The sensor must be mounted immediately next to the gas
cooler outlet to produce a correct signal.
Pressure reading (bar)
The pressure by the gas cooler must be measured using a pressure
transmitter type AKS 2050.
The pressure transmitter must be mounted immediately next
to the gas cooler outlet to produce a correct signal.
Emergency cooling
The valve's average opening degree for the last six hours is
regularly saved. This opening degree is used if there is a need for
emergency cooling.
EKC 326A	Manual	RS8FM602	©	Danfoss	02-2016	3

Examples

Simple heat recovery system

Partial heat recovery system

Heat recovery system (or heat pump system)

Manual RS8FM602 © Danfoss 02-2016

EKC 326A

Extra refrigeration capacity (“extra compressor”)

This function improves the system’s refrigeration capacity by increasing the reference pressure (Pgc Ref) in the gas cooler. The cooling performance increases to Q0+dh0.

The function also increases the load on the compressor motor as pressure increases. Power consumption increases to Qm+dQm.

Increasing pressure reference with heat recovery

The function will increase the gas pressure reference to the Pgc HR Min. value when it receives a signal.

The function is activated by an on/off signal at the voltage input.

Increasing pressure reference with heat recovery, variable reference

The function will increase the gas pressure reference to the value where it receives a signal.

The function is activated by a voltage signal between 0-10 V.

•Between 0-2 V it is regulated normally

•At 2 V the reference changes to the setting “Pc HR Min”

•At 10 V the reference will increase further using the setting “Pgc HR offset”

•Between 2-10 V the reference is variable.

EKC 326A

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