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Swithc between two thermostat band (two references)
It is a good idea to use this function for refrigeration appliances
containing impulse purchases where the products are often
exchanged. Via a switch function it is possible to change between
two thermostat settings depending on the products contained in
the appliance. The change-over between two thermostat bands
is activated via a contact or via a pulse signal of at least three
seconds' duration – as a rule via a key switch placed on the appli-
ance. When the switch is activated the thermostat settings as well
as the limits for the alarm thermostat and the product sensor will
change.
The changeover between the two thermostat bands can also be
seen on the display, but only if the shift is set to take place with a
pulse signal.
When a change-over is activated the display will show to which
thermostat band the change goes.
Displacement of reference for thermostat
In refrigeration appliances there may be big load differences
between the shop's opening and closing hours, especially if Night
blinds/curtains are used. The thermostat reference may be raised
here without it having any effect on the product temperature.
Change-over between day and night operation can take place, as
follows:
• via the built-in weekly schedule
• via an external switch signal
• via a signal from the data communication
When night operation starts the thermostat reference will be dis-
placed with an offset value that normally will be positive. It must
however be negative if cold accumulation is to take place.
When a Night blind is used the distribution of air in the appliance
will change radically. A change of the thermostat's weighted S3/
S4 ratio will therefore be required. As a rule the S4 share is set at a
lower value during the night than during the day.
The thermostat reference can be displaced via an external voltage
signal which is particularly useful for process cooling.
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RS8HP102 © Danfoss 2018-09
The signal may be a 0-5V, 0-10V, 1-5V or 2-10V voltage signal. Two
offset values must be set, one indicating the displacement at mini-
mum signal and another indicating the displacement at maximum
signal. The displacement will apply to all sections.
The displacement will not affect the alarm limits.
Melting function
This function will stop the air flow in the evaporator from being re-
duced by frost created by uninterrupted operation for a long time.
The function is activated if the thermostat temperature has
remained in the range between -5°C and +10°C for a longer
period than the set melting interval. The refrigeration will then be
stopped during the set melting period. The frost will be melted
so that the air flow and hence the evaporator's capacity will be
greatly improved.
The settings for melting interval and melting period are common
to all sections, but the controller will displace the melting time for
the different sections so that no synchronisation will take place.
If there are several controllers in the same defrost group the time
between the two meltings should be set differently in the indi-
vidual controllers. In this way a synchronisation of the thermostats'
cutin times will be avoided.
Timer for compressor relay
If a compressor relay has been selected, the relay's timer function
will have higher priority than the thermostat function.
AK-CC 750A
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