10
Manual RS8EN502 © Danfoss 02-2010
AK-CC 550
Refrigeration
Heat
Neutral zone
Digital inputs
There are two digital inputs DI1 and DI2 with contact function and
one digital input DI3 with high voltage signal.
They can be used for the following functions:
- Retransmission of contacts position via data communication
- Door contact function with alarm
- Starting a defrost
- Main switch - start/stop of cooling
- Night setback
- Thermostat bands switch
- General alarm monitoring
- Case cleaning
- Forced cooling
- Override of night blinds
- Coordinated defrost (DI2 only)
- Forced closing of valve (DI 3 only)
Forced closing
The AKV valves can be closed with an external signal ( "Forced
closing").
The function must be used in connection with the compressor’s
safety circuit, so that there will be no injection of liquid into the
evaporator when the compressor is stopped by the safety con
-
trols. (However not at low pressure – LP).
If a defrost cycle is in progress, the forced closing status will not be
re-established until the defrost is completed.
The signal can be received from the DI3-input or via the data com
-
munication.
During a forced closing the fans can be defined to be stopped or
in operation.
Door contact
The door contact function can via the digital inputs be defined for
two different applications:
Alarm monitoring
The controller monitors the door contact and delivers an alarm
message if the door has been opened for a longer period than
the set alarm delay.
Alarm monitoring and stop of refrigeration
When the door is opened the refrigeration is stopped, i.e. the
injection, the compressor and the fan are stopped and light
switch on.
If the door remains open for a longer time than the set restart
time, refrigeration will be resumed. This will ensure that
refrigeration is maintained even if the door is left open or if the
door contact should be defective. If the door remains open for
a longer period than the set alarm delay an alarm will also be
triggered.
Heating function
The heating function is used to prevent the temperature
becoming too low, e.g. in a cutting room, etc. The limit for when
the heating function cuts off is set as an offset value under the
current cutout limit for the refrigeration thermostat. This ensures
that refrigeration and heating do not occur simultaneously.
The difference for the heating thermostat has the same value
as for the refrigeration thermostat. To prevent that the heating
thermostat cuts in during short-term drops in air temperature a
time delay can be set for when to change from refrigeration to
heating.
