Daikin GCU2020PXB1 Installation, Commissioning And Maintenance Manual page 100

Consequently, the fi rst compressor in the parallel line can be controlled
by inverter. It is recommended to use a suction pressure set point value
for the parallel line that is the same as the receiver pressure set point for
proportional control, while the set point should be slightly lower than
the latter for neutral zone control (1 barg diff erence between the two set
points should be suffi cient).
If on the other hand there is a single parallel compressor managed
directly by the main board:
Parallel Compr. Cca01
Enable parallel
compressor:
Control mode:
Compressor control is proportional with integration error, P+I, and the
various settings, relating to:
•
times;
•
control;
•
inverter modulation;
•
alarms;
•
analogue output confi guration;
can all be found inside the same menu: C.Compressors
compression Ccaxy (see the parameter table)
The main variables used to manage activation and control of the parallel
compressor are:
•
gas cooler outlet temperature;
•
RPRV valve opening percentage;
•
receiver pressure set point.
The parallel compressor is activated when the following conditions are
true:
•
gas cooler outlet temperature above a settable threshold;
•
RPRV valve opening percentage above a settable threshold.
At the same time as the parallel compressor is activated, the receiver
pressure set point will be increased by a settable off set in a settable time.
Fig. 6.ax
Increasing the receiver set point results in the fl ash gas valve (RPRV) closing.
The parallel compressor is not aff ected by a decrease in the opening of
the RPRV valve, however remains active until parallel compressor control
reaches the set point (depending on how the controller is confi gured)
Fig. 6.ay
Copyright HPL March 2021
YES
INTERNAL
c.Parallel
T Gas Cooler > Settable TH
RPRV Opening > Settable TH
AUX Comp Activation
Receiver Setpoint Increase
T Gas Cooler > Settable TH
RPRV Opening > Settable TH
AUX Comp Activation
Receiver Setpoint Increase
If, on the other hand, the Gas Cooler outlet temperature falls below the
activation threshold, the card that manages the parallel compressor no
longer receives the enabling signal and thus switches off the parallel
compressor:
Oil diff erential management with parallel compression
The parallel compression function, either integrated (single compressor)
or via pLAN, can also be included in the common oil management by
diff erential pressure (also see paragraph 6.10.2), and is enabled on screen
Eaab25:
Diff erential oil pressure control by dedicated pressure probe, screen
Eeaa1a:
This manages the opening of the solenoid valve, screen Bac71.
This digital output is dedicated to the common solenoid valve installed
between the oil separator and oil receiver.
When the oil reservoir pressure approaches the threshold (delta) set on
screen Eaab14:
This will trigger the opening of the valve so as to pressurise the oil
reservoir and ensure correct oil fl ow to the compressors.
The delta is calculated based on the diff erence between the medium
temperature compressor suction pressure and the oil receiver pressure.
The status of the function can be checked on screen Aa61:
51
Page 100 of 179
T Gas Cooler > Settable TH
RPRV Opening > Settable TH
AUX Comp Activation
Receiver Setpoint Increase
Fig. 6.az
P41135 Rev 03
pRack PR300T +0300018EN rel. 1.5 - 02.05.2017
ENG