Fast Start (Speed Up); Silencer - Carel PRK300L3FK User Manual

Example 3: minimum modulating output value 2 V, maximum value 10 V,
minimum modulating device capacity 60 %, maximum 100 %.
Analog output
Max output
value = 10 V
Min capacity = 60 %
Min output
value = 2 V
Setpoint
Differential
Fig. 6.u
Cut-off
pRack pR300 manages a control cut-off for the fans; functions and related
parameter settings can be enabled from main menu branch D.a.b/D.b.b.
The operating principle of the cut-off function is shown in the fi gure:
Regulation request
Max output
value
Cut-Off value
of request
Cut-Off setpoint
Differential
A percentage of the control request and a cut-off set point can be set.
When the control request reaches the set cut-off value, this value is kept
constant until the control value falls below the cut-off set point, after
which it falls to 0 % and remains there until the request exceeds the cut-
off value again.
6.4.2 Rotation
pRack pR300 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 pR300 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 in paragraph 6.3.3: 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 described in
paragraph 6.4.5.
Max capacity = 100 %
Regulation
probe value
Differential
Regulation
Regulation setpoint
probe value
Differential
Fig. 6.v
6.4.3

Fast start (speed up)

pRack pR300 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/D.b.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.
6.4.4

Silencer

pRack pR300 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/D.b.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.
6.4.5 Split condenser
pRack pR300 can manage the possibility to exclude some fans from
operation, for example to reduce condenser 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/D.b.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)
Note:
•
the split condenser function can be disabled by parameter if the high
pressure prevention function is activated (see paragraph 8.3.3). 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.
6.4.6 Manual operation
pRack pR300 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 paragraph
6.3.9.
6.4.7 Alarms
pRack pR300 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. For details on the fan alarms, see Chapter 8.
43
ENG
pRack +0300025EN rel. 1.3 - 17.12.2015