CRD-XP
CRD-XP_2006-04_EN Subject to technical changes Page 9 of 16
No active temperature control
When the controller is used as a pure defrosting slave, the control can be switched to inactive. In this
operation mode, dashes represent the regulating actual value in the display. The control probe F1 is
not monitored. The defrosting synchronised by the master is terminated via the limit probe F2.
Recording of the measured temperatures and statuses in the history or in the historical storage
remains active.
Weighted control with 2 probes
Both probes F1 and F2 are used for control in the "Weighted control" operation mode. F1 measures
the supply air temperature, whereas F2 determines the return air temperature. The true regulating
actual value is calculated through a weighting of both probes. The weighting is set with 50% return air
in day operation and 60% return air in night operation. The supply air probe F1 is used as a limit probe
for defrosting. If one of the two probes malfunctions, the still-intact probe is used for control.
3-point control, heating/cooling
The defrosting output is used for the heating
operation. The cooling operation is active when the
actual value exceeds the setpoint by half the
hysteresis amount. When the setpoint is reached,
cooling is switched off again. Heating begins when
the regulating actual value falls below the setpoint
by half the hysteresis amount. It ends when the
setpoint is reached.
Initiation of defrosting is possible in this operation mode as well. If defrosting is not desired, the times
must be explicitly deleted. With forced air defrosting, there is no triggering of the defrosting output
(heat register). With electrical defrosting, the heating/defrosting output becomes active. F2 serves
here as a limit probe.
Sharp frost function
Input 2 can be configured via parameter P54 to trigger the sharp frost function. The desired sharp
freezing temperature is preset via P14. After input 2 is activated, the system is cooled down to the
sharp setpoint. There it plays no role whether the input is set only briefly or remains activated. If input
2 is still active when the sharp frost temperature is reached, controlling remains at the sharp frost
temperature. After the input is opened, the system is cooled again below the sharp frost setpoint and,
immediately after this, forced defrosting is initiated. If, in contrast, input 2 is only briefly set (at least 2
s) and then reopened, the device conducts forced defrosting immediately after falling below the sharp
temperature for the first time.
+
-
Cooling
T
actual
Heating
Setpoint
T
set
T
set
½
Hysteresis
T
set
½
Hysteresis
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