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6.14.1 ChillBooster
pRack PR300T can control the Carel ChillBooster, device used for
evaporative cooling of the air that fl ows through the condenser.
ChillBooster can be enabled and the related parameters set in main
menu branch E.g.
ChillBooster is activated when two conditions exist:
•
the outside temperature exceeds a set threshold
•
the fan control request is at the maximum for at least a settable
number of minutes
The maximum request time starts counting again whenever the request
decreases, therefore the request must remain at the maximum for at least
the set time. Activation ends when the request falls below a set threshold.
pRack PR300T can manage an alarm digital input from ChillBooster, the
eff ect of which is to deactivate the device.
As the number of operating hours of ChillBooster is critical as regards
formation of scale on the condenser, pRack PR300T can manage the
operating hour threshold, which should be set to 200 hours.
Hygiene procedure
To avoid water stagnation in the pipes, a hygiene procedure can be
enabled that activates ChillBooster every day for a set time, if the outside
temperature is greater than a threshold.
Note: if the outside temperature probe is not confi gured or is
confi gured but is not working, ChillBooster operates based solely on the
control request, and the hygiene procedure can still be activated.
The only diff erence between probe not confi gured and probe not
working concerns the ChillBooster operating without temperature probe
alarm, which is only generated when the probe is confi gured but not
working.
ChillBooster as the fi rst stage in high pressure prevention
ChillBooster can be used to prevent high condensing pressure. The
parameters relating to this function can be set in branch G.b.a/G.b.b in
the main menu, after having enabled the ChillBooster function. For details
on the prevent function see paragraph 8.3.3. Operation of ChillBooster as
the fi rst stage in high pressure prevention is Similar to the heat recovery
function described in paragraph 6.6.3. The function must be enabled and
an off set must be set in relation to the prevent.
6.15 Double line synchronization (DSS)
pRack pR300T can manage some synchronization functions between the
two lines:
•
Inhibition of contemporary compressor starts
•
Forcing the medium temperature line if the low temperature line is
activated
•
Turning off the low temperature line if the medium temperature line is
in a serious alarm condition
The three DSS functions can be enabled independently
Attention: in the pRack pR300T software, it is assumed that the medium
temperature line is line L1 while the low temperature line is L2.
DSS can be enabled and the relative parameters can be set from main
menu branch E.f.
Inhibition of the contemporary starts
The inhibition of contemporary starts of the compressor can be useful for
all system confi gurations with two separate lines and in cascading system
confi gurations. The function that prevents contemporary starts can be
enabled and a delay time can be set for compressor starts belonging to
diff erent lines.
Forcing the medium temperature line
Forcing the medium temperature line can be useful for cascading system
confi guration and, once enabled, can force the startup at minimum
power of at least one compressor in the medium temperature L1 line if at
least one compressor in the low temperature L2 line is on.
Copyright HPL March 2021
This means that before turning on the low temperature line, the DSS
forces at least one of the compressors in the medium temperature L1
line to turn on at minimum power. The low temperature L2 line thus has
greater priority in relation to the request coming from the regulation for
the medium temperature L1 line.
Turning off the low temperature line
Turning off the low temperature line is forced by the DSS if a serious alarm
occurs which turns off all of the alarms in the medium temperature line
or, in general, if the medium temperature line is OFF.
Enable pump-down on medium temperature line
During normal compressor rack operation, when at least one compressor
on the low temperature line is running, the medium temperature
compressor control will enable pump-down. If there is demand,
the minimum capacity step will be guaranteed, only if the medium
temperature line suction pressure is below a set threshold.
Note: in the event of failure of the pLAN network, the DSS is
disabled
6.16 EEVS: Electronic Expansion Valve
Synchronization
The new software for managing transcritical systems features the
possibility to manage the 2 stepper valves for high pressure and fl ash gas
control directly from the pRack controller. The built-in driver on PRK30TD***
controllers or the external driver (EVD) is controlled via fi eldbus. Direct
communication between controller and driver is used to synchronise
compressor rack operation and electronic expansion valve control.
Communication is managed inside the controller (on PRK30TD*** codes)
or via RS485 serial for external drivers. One single interface (pRack) can
thus be used to monitor / set the main parameters for the EVDEVO and
view them via the supervisor (Modbus communication). The FIELDBUS
DRIVER off ers the possibility to use 4 additional analogue inputs (S1, S2,
S3 and S4) directly from pRack.
Where:
S1 Probe 1 (pressure) or external 4 to 20 mA signal
S2 Probe 2 (temperature) or external 0 to 10 V signal (*)
S3 Probe 3 (pressure)
S4 Probe 4 (temperature)
6.16.1 HPV and RPRV valve connection
The HPV and RPRV valves can be connected:
•
directly, controlling the valves using a 0-10 V output on pRack
pR300T
V
out
V
out
V
out
V
out
24 Vac/Vdc
0 V
(*): If one of the two valves is controlled by the driver Carel, while the
other, just is controlled by a signal 0...10V, remember to disable the last
one from the driver with mask Ib99 during Wizard operation or mask
Eic01 if Wizard is completed.
•
via an EVD EVO driver confi gured as 0 to 10 V positioner to control Carel
stepper valves (pressure less than 45 barg) or third party valves (fi g. 2.f )
49
Page 98 of 172
J20
V
out
V
out
Fig. 6.at
P4114S Rev 03
pRack PR300T +0300018EN rel. 1.5 - 02.05.2017
ENG
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