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ENG
6.5.2
Rotation
pRack PR300T can manage rotation of the fans, much in the same way as
described for the compressors, therefore:
•
LIFO, FIFO, time, Custom rotation
•
Management of a modulation device on each line
The substantial diff erence compared to the compressors concerns
the possibility to manage diff erent capacities and load stages, which
are obviously not featured for the fans. In addition, pRack PR300T can
specially manage inverter driven fans. In fact, a multiple number of
inverter driven fans can be set.
If there is more than one fan, however the number of inverter driven fans
is set to 1, the fans are started and stopped at the same time, and the fans
will always all be at the same power.
If there is more than one inverter driven fan, as well as being able to
use an alarm digital input for each, it is assumed that the weight of the
modulating device is proportional to the number of fans, therefore the
fi rst case is applied, as described previously: fans all with the same power
and modulating device power variation range greater than or equal to
the capacity of the other devices.
Example 1: 4 fans all controlled by the same inverter correspond to
1 fan with four times the power.
Note: some fans can be excluded from the rotation, for example in
the winter; to do this use the split condenser function.
6.5.3
Fast start (speed up)
pRack PR300T can manage the fast start function (speed up), used to
overcome the initial inertia of the fans. The function can be enabled
and the related parameters set in main menu branch D.a.g If speed up is
enabled, a start time can be set in which the fan speed is forced to 100%.
If the outside temperature sensor is used, moreover, a threshold can be
set (with reset diff erential) below which speed up is disabled, so as to not
drastically lower the condensing pressure at start-up.
Note: speed up has lower priority than the Silencer function (see
the following paragraph for the details), therefore if the Silencer
function is active, this is disabled.
6.5.4
Silencer
pRack PR300T can manage the Silencer function, used to limit fan speed
at certain times of the day or in specifi c conditions, enabled by digital
input.
The function can be enabled and the related parameters set in main
menu branch D.a.g.
Enabling fan speed limitation from the digital input or based on time
bands is independent, consequently the speed is limited to the set value
when at least one of the two conditions is active.
Up to 4 activation bands can be set for each day of the week.
6.5.5
Split condenser
pRack PR300T can manage the possibility to exclude some fans from
operation, for example to reduce gas cooler operation in winter, using
the split condenser function.
The function can be enabled and the related parameters set in main
menu branch D.a.g.
Split condenser can be used to exclude from rotation fans whose index is:
•
even
•
odd
•
higher than a settable value
•
lower than a settable value
The function can be activated by:
•
time bands (winter/summer seasons)
•
digital input
•
supervisor
•
outside temperature (set threshold and diff erential)
Copyright HPL March 2021
pRack PR300T +0300018EN rel. 1.5 - 02.05.2017
Note:
•
the split condenser function can be disabled by parameter if the high
pressure prevention function is activated. If split condenser is disabled
due to activation of the high pressure prevention function, it remains
disabled for a set time, after which it is reactivated.
•
split condenser cannot be enabled if there is a speed modulation
device that controls all the fans.
6.5.6
Manual operation
pRack PR300T can also manage the same three manual operating modes
for the fans as described for the compressors:
•
Enabling
•
Manual management
•
Output test
Enabling is managed in main menu branch D.a.f/D.b.f., while manual
management and the output test can be activated in main menu branch
B.b or B.c. For the detailed description of the three modes, see paragr. 6.3.9.
6.5.7
Alarms
pRack PR300T can manage both a common alarm for the fans and
separate alarms for each fan.
When the common alarm is active the alarm is signalled, but no fan
is stopped, while for separate alarms the fan that the alarm refers to is
stopped.
6.6 HPV valve management
Management of the HPV valves, which separates the high pressure part of
the system from the medium pressure part, determines the transcritical
and subcritical operation mode of the unit. In transcritical mode, valve
regulation is done to obtain maximum yield while in subcritical mode,
regulation controls the subcooling. The HPV valve has a proportional +
integral (PI) type of regulation which uses an optimal pressure value of
the gas cooler calculated on the basis of the gas cooler pressure and
temperature as a regulation setpoint, as described hereafter.
Enabling HPV valve management coincides with enabling the transcritical
system management mode.
The HPV valve can be managed directly by pRack pR300T with built-
in driver (PRK30TD***) or with external EVD EVO driver. Both solutions
are compatible with the majority of valves available on the market.
Direct control via serial connection is enabled under EEVS (electronic
expansion valve settings), accessible from the main menu, branch E.i.c.
The confi guration parameters, on the other hand, are accessible from
the main menu, branch E.i. The algorithm for calculating the regulation
setpoint of the HPV valve can be optimized or customized by the user
according to what was set by the parameter.
Calculation of the optimized setpoint
The calculation of the optimized setpoint is illustrated in the fi gure.
T₂₃
D
40
Page 89 of 169
UPPER PROPORTIONAL ZONE
A
TRANSCRITICAL ZONE
T₁₂
B
INTERMEDIATE ZONE
C
SUBCRITICAL ZONE
HPV CLOSING ZONE
Enthalpy (KJ/Kg)
Fig. 6.ac
P4367 Rev 01
P₁₀₀
%
P
max
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