Carel Hecu CO2, User Manual

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28
ENG
Hecu
C O
2
+0300085EN rel. 2.2 - 07.05.2019
Safety functions (active only if "Independent start of compressors" is set
to YES):
Par. start for high
rec. pressure: Force the parallel compressor on in the event of high
pressure in the receiver even if the LT compressor is switched
off due to no request or alarms (default threshold: 60 barg,
settable).
Env. lim. for LT
high dis.
pressure: High pressure prevention based on the LT compressor en-
velope. Sets the condensing/discharge pressure limit at the
selected value, recommended threshold 45 barg (settable).
When the LT compressor discharge pressure exceeds the set
threshold, the controller begins to reduce compressor speed
in order to return to normal operating conditions (i.e. inside
the envelope). If the discharge pressure remains above the
set threshold, the compressor can be switched off due to the
envelope alarm (after the standard timeout for the envelope
alarm).
Threshold=0barg
Æ
function not active.
LT cut-off thr. If
par. can’t start: Cut-off due to LT compressor high pressure. The function is
activated when the parallel compressor is off due to timing or
alarms (default 50 barg, settable).
Tab. 6.d
Parallel compressor: fl oating set point
The receiver pressure and therefore the parallel compressor set point is
calculated according to the following relationship:
g g
6.5 Fans
Hecu CO2 can manage up to two fans with a speed modulation device,
which may be an inverter or a PWM phase control device. In the same way
as for the compressors, fan control can be proportional or proportional
plus integral, based on pressure or temperature.
Fan operation with modulating device
If the fans are controlled by a modulating device, the meaning of the
parameters that associate the minimum and maximum values of the
device’s modulating output and the minimum and maximum capacity
of the modulating device on screens Dg01 and Dg02 is illustrated in the
following examples.
Example 1: minimum modulating output value 0 V, maximum value 10 V,
minimum modulating device capacity 0%, maximum value 100%.
Differential Differential
Set point
Min capacity = 0%
Max capacity = 100%
Regulation
probe value
Analog output
Min output
value = 0 V
Max output
value = 10 V
Fig. 6.i
Example 2: minimum modulating output value 0 V, maximum value 10 V,
minimum modulating device capacity 60 %, maximum value 100%.
Differential Differential
Set point
Min capacity = 60%
Max capacity = 100%
Regulation
probe value
Analog output
Min output
value = 0 V
Max output
value = 10 V
Fig. 6.j
Example 3: minimum modulating output value 2 V, maximum value 10 V,
minimum modulating device capacity 60 %, maximum value 100%.
Differential Differential
Set point
Min capacity = 60%
Max capacity = 100%
Regulation
probe value
Analog output
Min output
value = 0 V
Max output
value = 10 V
Fig. 6.k