CB-110-438
Apart from the basic settings, at least the following
parameters must be set for direct control:
• Refrigerant
• Evaporation temperature
• Pump down cut-out temperature
• Condensing temperature
The compressor control is based on the so-called pump
down logic. For this, the digital start input of the com-
pressor (DI1) must be permanently closed or a control
switch can be used for release. The compressor is
switched on as soon as the evaporation temperature
exceeds the setpoint and stops when the evaporation
temperature falls below the set pump-down cut-out
temperature.
During operation, the frequency inverter controls the
set evaporation temperature by regulating the com-
pressor frequency and by switching the uncontrolled
compressor on/off (relay on the extension module, Ter-
minal 5+6). The uncontrolled compressor is switched
on/off if the VARIPACK compressor runs on maximum/
minimum frequency for the configured time set in
P8-04/P8-05. The control speed can be adjusted to the
requirements by setting the P band (P3-06) and the I
band (P3-07). Moreover, the time delays of the uncon-
trolled compressor can be adapted by the parameters
"switch-on delay" (P8-04) and "switch-off delay"
(P8-05).
The analogue output AO1 (connection of a variable-
speed condenser fan) can be used to control the set
condensing temperature via the 0...10V signal. In or-
der to guarantee the most efficient level of operation, it
is recommended to set the nominal condensing tem-
perature according to the minimum permitted condens-
ing temperature of the compressors if the system al-
lows doing so. If the condensing temperature exceeds
the setpoint, the rotational speed of the fans is in-
creased accordingly. The quality of the control can be
optimized by setting the P band (P3-13) and the I band
(P3-14) to the system inertia. In addition, a minimum
fan speed (P3-16) can be set, if necessary.
"Evaporation temperature setpoint 2" (P3-03)
The evaporation temperature setpoint 2 is activated by
a signal to the input DI4 (extension module terminal 1).
"Condensing temperature setpoint 2" (P3-09)
The condensing temperature setpoint 2 is activated by
a signal to the input DI5 (extension module terminal 2).
This value can be used, for example, as setpoint for
heat recovery.
"Condensing temperature limiter" (P3-11)
The condensing temperature limiter reduces the com-
pressor frequency as soon as the set condensing tem-
perature is exceeded. Thus a high pressure cut-out can
be avoided in many cases since the load on the con-
denser is reduced by lowering the frequency.
"Electronic low pressure switch" (P3-05)
The low pressure switch function switches the com-
pressor off as soon as the pressure falls below the set
pressure value. In contrast to the pump down shut-off,
the compressor is immediately switched off as soon as
this limit value is reached and is not shut down via the
ramp. Moreover, a fault is stored in the fault memory of
the frequency inverter. As soon as the evaporation tem-
perature setpoint is exceeded, the compressor is re-
started.
"Electronic high pressure switch" (P3-12)
The high pressure switch function switches the com-
pressor off as soon as the set pressure value is ex-
ceeded. The standard setting and the maximum ad-
justable value correspond to the maximum operating
pressure of the compressor. The high pressure switch
is reset as soon as the temperature falls below the set
value of the condensing temperature limiter.
Information
The electronic high pressure switch function
does not replace the type-examination tested
high pressure switch according to EN378!
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