Danfoss EKC 331T Capacity Controller

Introduction

Application

The controller is used for capacity regulation of compressors or condensers in small refrigerating systems. Regulation can be carried out with up to four identical capacity steps.

Advantages

• Patented neutral zone regulation
• Sequential or cyclic operation

Functions

• Regulation: Regulation with up to four relay outputs can be carried out. Regulation takes place with a set reference which is compared to a signal from a pressure transmitter or a temperature sensor.
• Relay module: It is possible to use the controller as a relay module, so that the relays are cut in or out by means of an external voltage signal.
• Alarm function: A relay becomes activated when the set alarm limits are exceeded.
• Digital input: The digital input can be used for:
  • Night operation where the suction pressure is raised
  • Heat recovery where the condensing pressure is raised
  • External start/stop of the regulation.
  • Monitoring of safety circuit
• Reverse function: The regulation can be reversed so that the relays are activated in case of falling temperature, rather than by the rising temperature.
• Possibility of data communication

Display

A signal from a pressure transmitter will always be converted and shown as a temperature value. Settings are made as for temperature values.

Function: Capacity Regulation

The cut-in capacity is controlled by signals from the connected pressure transmitter (temperature sensor) and the set reference. Outside the reference, a neutral zone is set where the capacity will neither be cut in nor out.

Outside the neutral zone (in the hatched areas named +zone and -zone), the capacity will be cut in or out if the regulation registers a change of pressure (or temperature) "away" from the neutral zone. Cut-in and cut-out will take place with the set time delays. If the pressure (or temperature) however "approaches" the neutral zone, the controller will make no changes of the cut-in capacity.

If regulation takes place outside the hatched area (named ++zone and --zone), changes of the cut-in capacity will occur somewhat faster than if it were in the hatched area.

Cut-in of steps can be defined for either sequential or cyclic operation.

Diagram: Capacity Regulation Zones illustrates pressure/temperature zones relative to a reference (REF). The zones are: ++Zone (fastest response), +Zone (response), NZ (Neutral Zone), -Zone (response), --Zone (fastest response). Arrows indicate pressure/temperature changes and their effect on capacity regulation.

Operating Modes

Sequential Operation

Relays are cut in sequentially (1, 2, 3, etc.). Cut-out occurs in the opposite sequence (last cut-in relay is cut out first).

Diagram: Sequential Operation shows capacity steps (R1, R2, R3, R4) increasing over time, illustrating sequential cut-in. The corresponding cut-out phase shows the reverse sequence.

Cyclic Operation

Relays are coupled to equalize operating time. At each cut-in, the relay with the least operating time is selected. At each cut-out, the relay with the most operating time is selected.

Rx represents a random relay, and h represents the number of hours.

Diagram: Cyclic Operation shows capacity steps (R1, R2, R3, R4) with varying operating hours (h, h+, h++, h+++), illustrating how the relay with the least time is chosen for cut-in and the one with the most time for cut-out.

Compressor and Unloader Operation

For capacity regulation on two compressors with one unloader each:

• Relays 1 and 3 are connected to the compressor motors.
• Relays 2 and 4 are connected to the unloaders.
• Relays 1 and 3 operate to equalize operating time between the two compressors.

C = compressor, L = Unloader.

Diagram: Compressor and Unloader Operation illustrates the relationship between compressor (Ch, Ch+) and unloader (Lh, Lh+) states over time, showing how unloaders are managed in conjunction with compressor operation.

Relay Module

The controller can function as a relay module, with relays activated by an external voltage signal connected to terminal 15-16. Hysteresis at coupling points prevents unwanted relay switching.

Survey of Functions

Normal Display

Shows the signal from the pressure transmitter/temperature sensor. If used as a relay module, 'Uin' appears.

Pressure Regulation

Capacity Settings

Detailed Function Settings

Setting for Neutral Zone Regulation

Manual Control of Compressor Capacity

Alarm Settings

Miscellaneous

Controller Settings and Operation

DI Input Usage

The digital input can be connected to a contact function, and the contact can now be used for one of the following functions:

• 0: DI input not used
• 1: Regulation reference displaced when contact is cut in
• 2: Regulation is started and stopped when the contact is cut in and out, respectively.
• 3: Monitoring of the compressor's safety circuit. When the contact on the DI input cuts out, all relay outputs will immediately be cut out. At the same time, the alarm will sound.

Parameter: o22, Function: Di control

Operating Hours

The operating hours for the four relays can be read in the following menus. The read value is multiplied by 1000 to obtain the number of hours. On reaching 999 hours, the display stops and must be reset to 0. There will be no alarm or error message for counter overflow.

(In the AKM display, the hour number has not been multiplied)

• Value for relay number 1: Parameter: o23, Function: DO 1 run hour
• Value for relay number 2: Parameter: o24, Function: DO 2 run hour
• Value for relay number 3: Parameter: o25, Function: DO 3 run hour
• Value for relay number 4: Parameter: o26, Function: DO 4 run hour

Refrigerant Setting

Before refrigeration is started, the refrigerant must be defined. You may choose between the following refrigerants:

Parameter: o30, Function: Refrigerant

List of refrigerants (e.g., 1=R12, 2=R22, ..., 37=R407F). Warning: Wrong selection of refrigerant may cause damage to the compressor.

Manual Control

From this menu, relays can be cut in and out manually. OFF gives no override, but a number between 1 and 4 will cut in a corresponding relay. The other relays will be off.

Parameter: o18

Frequency

Set the net frequency.

Parameter: o12, Function: 50/60 Hz (50=0, 60=1)

Address

If the controller is built into a network with data communication, it must have an address, and the master gateway must know this address. These settings can only be made when a data communication module has been mounted and the cable installation is completed (see document "RC.8A.C"). The address is set between 1 and 60. The address is sent to the gateway when the menu is set to ON.

Parameter: o03

Access Code

To protect settings with a numerical code, set a value between 0 and 100. To cancel, set to OFF.

Parameter: o05

Cooling or Heating

Cooling: Relays are cut in when the temperature is above the reference. Heating: Relays are cut in when the temperature is below the reference.

Parameter: o07, Function: Refg./Heat

Operating Status and Alarms

Operating Status

The controller displays status codes when waiting for the next regulation point. Push the upper button briefly (1s) to view status codes. The individual status codes have the following meanings:

Alarm Messages

Service

• u07: Voltage signal on the analogue input
• u10: Status on DI- input
• u15: Status on relay output DO1
• u25: Signal on pressure transmitter input (bar / PSIG)
• u58: Status on relay output DO2
• u59: Status on relay output DO3
• u60: Status on relay output DO4
• u62: Status on relay output "alarm"

Warning! Direct start of compressors

To prevent compressor breakdown, parameter c01 and c07 should be set according to supplier requirements or in general:

• Hermetic Compressors: c07 min. 5 minutes
• Semihermetic Compressors: c07 min. 8 minutes and c01 min. 2 to 5 minutes (Motor from 5 to 15 KW)

*) Direct activating of solenoid valves does not require settings different from factory (0).

Emergency Procedure

If the controller registers irregularities in the registered signals, it will start an emergency procedure:

For compressor regulation:

• If the signal from the temperature sensor/pressure transmitter becomes smaller than expected, the controller will continue operating with the average capacity that has been cut in during the past 60 minutes. This cut-in capacity will gradually decline as time passes.
• If the signal becomes smaller than the set value of A11, the capacity will instantly be cut out.

For condenser regulation:

• If the signal from the temperature sensor/pressure transmitter becomes smaller than expected, or if the condensing pressure becomes bigger than the set value of A10, the entire capacity will instantly be cut in.

Operation and Menu Survey

Display

Values are shown with three digits. The setting determines whether temperature is shown in °C or °F.

Display: A three-digit numerical display.

Light-emitting diodes (LED) on front panel

Four LEDs indicate when relays are operated. All LEDs flash if there is an error. Error codes can be uploaded to the display and alarms cancelled by pushing the top button briefly.

Controller Messages

The Buttons

To change a setting, use the two buttons to increase or decrease the value. Access the menu by pushing the upper button for a couple of seconds. Find the parameter code and push both buttons simultaneously to change the value. Save the new value by pushing both buttons simultaneously again.

• [Menu/Alarm Reset]: Gives access to the menu (or cuts out an alarm).
• [Change]: Gives access to changes.
• [Save]: Saves a change.

Examples of Operations

Set the regulation's set point

1. Push the two buttons simultaneously.
2. Push one of the buttons and select the new value.
3. Push both buttons again to conclude the setting.

Set one of the other menus

1. Push the upper button until a parameter is shown.
2. Push one of the buttons and find the parameter you want to change.
3. Push both buttons simultaneously until the parameter value is shown.
4. Push one of the buttons and select the new value.
5. Push both buttons again to conclude the setting.

Menu Survey

Data

Service

Factory setting

To return to factory-set values:

• Cut out the supply voltage to the controller.
• Keep both buttons depressed simultaneously while reconnecting the supply voltage.

Data

*) Pressure transmitter: As pressure transmitter can be used AKS 3000 or AKS 33 (AKS 33 has a higher accuracy than AKS 3000). It is also possible to use an AKS 32R. Please refer to catalogue RKOYG...

Ordering

Connections

Necessary connections

Terminals:

• 25-26: Supply voltage 230 V a.c.
• 3-10: Relay connections no. 1, 2, 3 and 4
• 12-13: Alarm relay. There is connection between 12 and 13 in alarm situations and when the controller is dead.

Control signal (see also o10)

Either terminals:

• 14-16: Voltage signal from AKS 32R
• 17-18: Current signal from AKS 3000 or AKS 33
• 15-16: Sensor signal from AKS 21, AKS 12 or EKS 111
• 15-16: Voltage signal from an other regulation.

External contact function, if applicable

19-20: Contact function for displacement of reference or start/stop of the regulation or for monitoring of safety circuit.

Data communication, if applicable

21-22: Mount only, if a data communication module has been mounted. It is important that the installation of the data communication cable be done correctly. Cf. separate literature No. RC8AC...

Diagram: Controller Connections shows terminal blocks and connections for supply voltage, relays, alarm, control signals (AKS 32R, AKS 33, AKS 21, 0-10V), DI input, and data communication.

General Information

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