22
ENG
“EVD evolution” +030222041 - rel. 1.0 - 01.06.2008
Auxiliary control 5.4
Auxiliary control can be activated at the same time as main control, and
uses the sensors connected to inputs S3 and/or S4.
Parameter/description Def.
CONFIGURATION
Auxiliary control:
Disabled; High condensing temperature protection on S3;
Modulating thermostat on S4; Backup sensors on S3 & S4
Disabled
Tab. 5.h
For the high condensing temperature protection (only available with
superheat control), an additional pressure sensor is connected to S3 that
measures the condensing pressure.
For the modulating thermostat function (only available with superheat
control), an additional temperature sensor is connected to S4 that
measures the temperature on used to perform temperature control (see
the corresponding paragraph).
The last option (available always) requires the installation of both sensors
S3 & S4, the first pressure and the second temperature.
Note: if only one backup sensor is fitted, under the manufacture
parameters, the sensor thresholds and alarm management can be set
separately.
HITCond protection (high condensing temperature)
The functional diagram is shown below.
S2
S3
S1
EVD
evolution
P
P
E
V
S
F
L
M
T
CP
C
EEV
Fig. 5.h
Key:
CP Compressor EEV Electronic expansion valve
C Condenser V Solenoid valve
L Liquid receiver E Evaporator
F Dewatering filter P Pressure sensor (transducer)
S Liquid indicator T Temperature sensor
For the wiring, see paragraph 2.7 “General connection diagram”.
As already mentioned, the HITCond protection can only be enabled if the
control measures the condensing pressure/temperature, and responds
moderately by closing the valve in the event where the condensing
temperature reaches excessive values, to prevent the compressor from
shutting down due to high pressure. The condensing pressure sensor
must be connected to input S3.
Modulating thermostat
This function is used, by connecting a temperature sensor to input
S4, to modulate the opening of the electronic valve so as to limit the
lowering of the temperature read and consequently reach the control
set point. This is useful in applications such as the multiplexed cabinets
to avoid the typical swings in air temperature due to the ON/OFF control
(thermostatic) of the solenoid valve. A temperature sensor must be
connected to input S4, located in a similar position to the one used for
the traditional temperature control of the cabinet. In practice, the close
the controlled temperature gets to the set point, the more the control
function decreases the cooling capacity of the evaporator by closing the
expansion valve.
By correctly setting the related parameters (see below), a very stable
cabinet temperature can be achieved around the set point, without ever
closing the solenoid valve. The function is defined by three parameters:
set point, differential and offset.
Parameter/description Def. Min. Max. UOM
SPECIAL
Modulating thermostat: set point 0 -60
(-76)
200
(392)
°C (°F)
Modulating thermostat: differential 0,1 0,1
(0,2)
100
(180)
°C (°F)
Modulating thermostat: superheat set
point offset (0= function disabled)
0 0 (0) 100
(180)
K (°R)
Tab. 5.i
The first two should have values similar to those set on the controller for
the cabinet or utility whose temperature is being modulated.
The offset, on the other hand, defines the intensity in closing the valve as
the temperature decreases: the greater the offset, the more the valve will
be modulated. The function is only active in a temperature band between
the set point and the set point plus the differential.
Important: the “Modulating thermostat” function should not be
used on stand-alone refrigeration units, but only in centralised systems.
In fact, in the former case closing the valve would cause a lowering of the
pressure and consequently shut down the compressor.
Examples of operation:
offset too low (or function 1.
disabled)
S4
t
t
OFF
set point
set point + diff
ON
F
offset too high2.
S4
t
t
OFF
set point
set point + diff
ON
F
offset correct3.
S4
t
t
OFF
set point
set point + diff
ON
F
Key:
diff= differential
F= modulating thermostat function
S4= temperature
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