Carel Hecu CO2, User Manual

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33
ENG
Hecu
C O
2
+0300085EN rel. 2.2 - 07.05.2019
Vice-versa, if the receiver pressure rises above the set maximum operating
pressure threshold, the dynamic set point calculated for the HPV valve
can be adjusted, so as to decrease the pressure inside the receiver.
An off set proportional to the deviation from the maximum threshold is
added to the calculated set point, so that closing the HPV valve further
decreases the pressure in the receiver.
The off set is directly proportional to the deviation from the maximum
operating threshold, as shown in the fi gure:
OFFS
Setpoint HPV
P
REC
P
REC
max
Fig. 6.v
S
ummary of HP
V
valve inputs, outputs and parameters
Below is a summary of the inputs/outputs and parameters used, together
with the corresponding confi guration screens. For details, see Appendix
A.1.
Summary of HPV valve inputs, outputs and parameters
Screen Description
Analogue inputs Bab07,
Da39 Gas cooler pressure
Bab10 Gas cooler outlet temperature
Bab09,
Da40 Gas cooler backup pressure
Bab15 Backup outside temperature
Digital inputs Baade,
Fha04 HPV valve alarm
Analogue out-
puts Bad02,
Fha06 Valve HPV output
Digital outputs --- ---
Parameters
Set Fhb01 Enable HPV valve management, i.e. enable tran-
scritical operating mode
Select the type of algorithm to be applied for
calculating the pressure set point
Defi nition
of the zones Fhb05-06 P
100%
upper pressure limit
P
max
pressure for the defi nition of the upper
proportional zone
P
critic
optimum pressure calculated at the transition
temperature between the intermediate zone and
the transcritical zone
T
12
limit temperature between transcritical zone
and intermediate zone
T
23
limit temperature between intermediate zone
and subcritical zone
T
min
temperature for the defi nition of the lower
proportional zone
Fhb07 T
100%
temperature for the defi nition of the valve
complete opening zone
Subcooling delta for optimised control
Coeffi cient for determining the custom curve
Parameters
Control Fhb08 Proportional gain for propor integral HPV
valve control
Integral time for propor integral HPV valve
control
Screen Description
Safety features Fhb02 Minimum HPV valve opening with unit ON
Minimum HPV valve opening with unit OFF
Fhb04 HPV valve opening at start-up during pre-posi-
tioning
Pre-positioning duration
Fhb09 Enable fi lter action on HPV valve set point
Number of samples
Fhb13 HPV valve safety position
Fhb14 Off set to be applied to the outside temperature in
the event of a gas cooler temperature probe error
Fhb15 Enable HPV valve safety procedures
Fhb16 High receiver pressure threshold
Maximum receiver pressure allowed
Maximum off set to be added to the HPV set point
when the receiver pressure exceeds the high
pressure threshold
Fhb17 Low receiver pressure threshold
Minimum receiver pressure allowed
Maximum off set to be subtracted from the HPV
set point when the receiver pressure falls below
the low pressure threshold
Safety features Fhb18 HPV valve closing enabled when all line 1 com-
pressors are off
HPV valve closing delay when all line 1 compres-
sors are off
Fhb20 Enable the warning function when the gas cooler
pressure is too far away from the set point for the
set time
Diff erence between gas cooler pressure and set
point to generate the warning
Delay time before generating the warning
Fhb03 Maximum HPV valve opening
Maximum variation per second allowed for HPV
valve output
Fhb30 Maximum HPV valve control set point
Enable valve position (delay threshold)
Fhb10 Minimum HPV valve control set point
Enable low temperature control (lower propor-
tional zone)
Tab. 6.e
6.8 RPRV valve management
The RPRV valve is managed with PI control so as to keep the pressure
inside the CO
2
receiver at the set point.
The RPRV valve can be managed directly by Hecu CO2 via the driver
integrated into the controller.
RPR
V
valve auxiliary functions
RPRV valve management includes some auxiliary functions:
• Pre-positioning : when switching the unit ON, the RPRV valve remains
in a fi xed position set by parameter for a set time, so as to be able
to quickly increase the pressure in the receiver. This procedure is
reactivated whenever the unit switches OFF or the RPRV valve is reset
to the minimum position when all of the compressors stop.
• Close valve with compressors off : if all of the medium temperature
compressors are switched off , the RPRV valve can move to the
minimum opening when ON, which can be set by parameter. When
a compressor restarts, valve control resumes, with the pre-positioning
procedure described in the previous point.
• Minimum and maximum opening values : the minimum opening
when OFF (from keypad, digital input or supervisor) and when ON can
be diff erentiated, while there is only one maximum opening value.
• Maximum percentage variation : the valve movement cannot exceed
the set maximum percentage variation per second.
• Maximum receiver pressure : a maximum value can be set for the
receiver pressure, beyond which an alarm is signalled and the unit can
be shutdown. Shutdown is optional and can be enabled by parameter.
S
ummary of RPR
V
valve inputs, outputs and parameters
Below is a summary of the inputs/outputs and parameters used, together
with the corresponding confi guration screens. For details, see chapter 6
and Appendix A.1.