Danfoss EKC 331 User guide

Capacity controller

EKC 331

REFRIGERATION AND AIR CONDITIONING

Manual

Introduction

Application

The controller is used for capacity regulation of compressors or condensers in small refrigerating systems.

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.

• Relay module

It is possible to use the controller as relay module, so that the relays are cut in or out by means of an external voltage signal.

• Alarmfunction

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.

Function

Capacity regulation

The cut-in capacity is controlled by signals from the connected pressure transmitter 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 “away” from the neutral zone. Cutin and cutout will take place with the set time delays.

If the pressure however “approaches” the neutral zone, the controller will make no changes of the cut-in capacity.

The size of the +zone and -zone is identical and defined to be constantly 0.7 times the set value of the neutral zone.

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. The set time delays will here be reduced by factor 0.3.

Cutin of steps can be defined for either sequential or cyclic operation.

Relay module
The controller can also be used as a relay module where the relays
in the module will then be controlled by the received voltage
signal.
Depending on the definition of the signal and the number of
relays used, the relays will be “distributed” over the signal.
A hysteresis around the individual cutin and cutout points will
ensure that the relay will not cut in or out when it is not called for.
2	Manual	RS.8A.G2.02	©	Danfoss	10-2000	EKC 331

Survey of functions

Function	Para-	Parameter by operation via data
	meter	communication
Normal display
Normally the signal from the pressure transmitter is shown. If the controller is used as		Pressure
relay module, Uin will appear on the display.
Pressure regulation		Reference
Regulation reference	-	Press. set point
Regulation is based on the set value.
(Push both buttons simultaneously to set the menu.)
Neutral zone	r01	Neutral zone
There is a neutral zone around the reference. See also page 2.
Displacement of reference	r13	Pressure o set
The set reference may be displaced with a fixed value when a signal is received at the
DI input. Regulation will then be based on the set reference plus the value set here.
The total reference can be seen when you push the lower of the two buttons. (Cf. also
Definition of DI input).
Reference limitation
The controller’s setting range for the reference can be narrowed down, so that you
cannot accidentally set a too high or too low value - that may result in damage to the
system. With these settings the reference can only be set between the two values.
Max. permissible reference value.	r02	Max. set point
Min. permissible reference value.	r03	Min. set point
Pressure unit	r05	Unit
Here you can select whether the controller is to indicate the pressure in bar or psig.		bar=0
(When psig is selected, the settings must also be in psig).		psig=1
		(In AKM only bar is used, whatever the
		setting).
Alarm		Alarm settings
The controller can give alarm in di erent situations. When there is an alarm all the
light-emitting diodes (LED) will flash on the controller front panel, and the alarm relay
will cut in.
Upper deviation	A10	Max. pressure
Here you set when the alarm at high pressure is to enter into e ect. The value is set as
an absolute value.
See also emergency procedure page 5.
Lower deviation	A11	Min. pressure
Here you set when the alarm at low pressure is to enter into e ect. The value is set as
an absolute value.
See also emergency procedure page 5.
Alarm delay	A03	Alarm delay
If one of the two limit values is exceeded, a timer function will commence. The alarm
will not become active until the set time delay has been passed. The time delay is set
in seconds.
Give the top button a brief push to zeroset the alarm and to have the message shown		Reset alarm
on the display.		The function zerosets all alarms when
		set in pos. ON.
		Alarm relay
		Here you can read the status of the
		alarm relay.
		(ON indicates operation with alarm).
		With data communication the impor-
		tance of the individual alarms can be
		defined. Setting is carried out in the
		“Alarm destinations” menu. See also
		page 8.

EKC 331

Manual RS.8A.G2.02 © Danfoss 10-2000

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