Daikin GCU2020PXB1 Installation, Commissioning And Maintenance Manual page 134

8.3.2 Pressure alarms from probe
The parameters corresponding to these alarms can be set in branch
C.a.e/C.b.e of the main menu for the suction pressure and D.a.e/D.b.e for
the condensing pressure.
For these types of alarms, reset is automatic and the activation threshold
and diff erential can be set, as well as the type of threshold, which may be
absolute or relative to the control set point. The fi gure shows an example
of setting the threshold to relative.
HP
Relative threshold
Setpoint
Fig. 8.d
Note: for temperature control, the alarms from probe are managed
based on temperature even when pressure probes are fi tted.
The eff ects of the diff erent pressure alarms from probe are described
below.
Low suction pressure from probe
The low suction pressure alarm from probe has the eff ect of stopping all
the compressors, ignoring the times.
High suction pressure from probe
The high suction pressure alarm from probe has the eff ect of forcing
all the compressors on, ignoring the control times, but observing the
compressor protection times.
Low condensing pressure from probe
The low condensing pressure alarm from probe has the eff ect of stopping
all the fans, ignoring the times.
High condensing pressure from probe
The high condensing pressure alarm from probe has the eff ect of forcing
all the fans on and stopping all the compressors, ignoring the times. The
reference for the alarm will be the discharge pressure probe (Bab75 or
Bbb75), or if this is not confi gured, the gas cooler / intercooler pressure
probe (Bab04 and Dba39).
8.3.3 High pressure prevention
pRack PR300T can manage 3 types of high condensing pressure
prevention actions, involving:
•
overriding the compressors and fans
•
activating heat recovery
•
activating ChillBooster
Prevent by overriding the compressors and fans
The parameters relating to this function can be set in branch G.b.a/G.b.b
of the main menu.
The eff ect of this type of prevent action is to force all the fans on at
maximum and switch all the compressors off , except for the minimum
capacity stage, ignoring the control times but observing the compressor
protection times. The minimum capacity stage means one compressor in
the case of compressors without capacity control and modulation devices,
or the minimum capacity stage for capacity-controlled compressors (e.g.
25%), or alternatively the minimum output of the modulation device in
the case of inverters, Digital Scroll
As well as the activation threshold, which is always absolute, and the
activation diff erential, a compressor deactivation time can be set,
corresponding to the time needed to switch off all the compressors,
except for the minimum capacity stage.
In addition, both the monitoring time and the number of activations in
the specifi ed period can be set. If the number of activations is higher,
reset becomes manual.
Copyright HPL March 2021
Pressure
Differential
Alarm
TM
.
Prevent by activating heat recovery
The parameters corresponding to this function can be set in branch
G.b.a/G.b.b of the main menu, if the heat recovery function is present.
As well as enabling the function, an off set from the activation threshold
for the prevent by overriding devices function must be set. The activation
diff erential for this function is the same as set for the prevent by overriding
devices function.
When reaching the threshold, pRack PR300T activates the heat recovery
function, if the conditions allow.
Prevent by activating ChillBooster
The parameters relating to this function can be set in branch G.b.a/G.b.b
of the main menu, if the ChillBooster function is present.
As well as enabling the function, an off set from the activation threshold
for the prevent by overriding devices function must be set. The activation
diff erential for this function is the same as set for the prevent by overriding
devices function.
When reaching the threshold, pRack PR300T force activates the
ChillBooster, if the conditions allow.
The following fi gure illustrates the activation thresholds for the prevent
function and the safety devices:
Pressure
85
Page 134 of 179
HP by pressostat
HP by probe
Prevent
Offset
Heat reclaim
or ChillBooster
time
Fig. 8.e
P41135 Rev 03
pRack PR300T +0300018EN rel. 1.5 - 02.05.2017
ENG