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ENG
•
CFloating condensing without heat recovery: SP=Tout+ΔT (screen
Dad06)
•
Floating condensing during heat recovery (acting on GC):
SP=Tout+Off setGC; where Off setGC> ΔT
•
As the last step of the heat recovery function, the Gas Cooler can be
bypassed when the following conditions are true:
•
bypass is enabled (screen Eeab)
•
the heat demand percentage exceeds a settable limit value (e.g. 90%)
•
the bypassed gas temperature cooler is lower than a certain settable
limit value (e.g. 20°C)
When these conditions are true, the bypass valve will start modulating,
with its set point being calculated based on the bypassed Gas Cooler
temperature, until the Gas Cooler is completely bypassed when the
temperature allows.
When heat recovery is deactivated, the HPV valve set point gradually
returns to the calculated value, over a settable time. The same is also true
for the condenser control set point.
6.14 Generic functions
pRack pR300T allows the use of free inputs/outputs and some internal
variables for generic functions.
Attention: generic functions are available on the pRack pR300T
boards with pLAN address from 1 to 4, or on all boards that manage
a suction or condensing line, however only the parameters related to the
functions managed by boards 1 and 2 are sent to the supervisor system.
The generic functions available for each board are:
•
5 stages
•
2 modulations
•
2 alarms
•
1 scheduler
Each function can be enabled/disabled by digital input or user interface.
The functionalities can be enabled and the relative parameters can be set
from main menu branch E.f.
To be able to use the free inputs they must be confi gured as generic
probes from A to E (analog inputs) and generic inputs from F to J (digital
inputs), so a maximum of 5 analog and 5 digital inputs can be used.
After having confi gured the generic probes, the variables associated
with them can be used as regulation variables and the digital inputs
as enabling variables. Besides the probes and generic inputs, internal
variables in the pRack pR300T software can be used, which depend upon
the confi guration of the system. Some examples, for analog variables, are:
•
Suction pressure
•
Gas cooler pressure
•
Saturated suction temperature
•
Gas cooler temperature
•
Suction temperature
•
Discharge temperature
•
% of compressors active
•
% of fans active
•
Superheating
•
Subcooling
•
Liquid temperature
•
% requested compressors
•
% requested fans
for digital variables:
•
High suction pressure alarm
•
Low suction pressure alarm
•
High gas cooler pressure alarm
•
Low gas cooler pressure alarm
•
Sign of life
•
Prevent active
A unit of measure and description can be associated to each generic
function. The following shows the operation of 4 types of generic
functions.
Copyright HPL March 2021
pRack PR300T +0300018EN rel. 1.5 - 02.05.2017
Stages
pRack pR300T can manage up to 5 stage functions, with either direct or
reverse operation.
In both cases a setpoint and diff erential can be set and the operation of
the related output is illustrated in the fi gure for both cases:
Direct stage
Diff.
Setpoint
Reverse stage
Diff.
Setpoint
If an enabling value is set, the output connected to the stage is active if
the enabling is also active. For each stage, a high alarm and low alarm
threshold can be enabled and they are absolute. For each alarm, the
activation delay and priority can be set. See Chapter 8 for details on the
alarms. An example of using the generic stage functions may be the
activation of the fans on the room units based on the temperature.
Modulation
pRack pR300T can manage up to 2 modulation functions, with either
direct or reverse operation. In both cases a setpoint and diff erential can
be set and the operation of the related output is illustrated in the fi gure
for the direct mode, where the cut-off function is also enabled:
Direct modulation
MAX
MIN
(Cut-off
Value)
Hyster.
Cutoff differential
If an enabling value is set, the output connected to the stage is active if
the enabling is also active. For each modulation, a high alarm and low
alarm threshold can be enabled and they are absolute. For each alarm,
the activation delay and priority can be set. See Chapter 8 for details on
the alarms. For modulation, a minimum and maximum value can also
be set for the output and the cut-off function can be enabled, which
operates as shown in the previous fi gure.
Alarms
pRack pR300T can manage up to 2 alarm functions, for which a digital
variable to be monitored, activation delay, priority and any description can
be set. A digital output can be associated to each general alarm function
for the activation of external devices when the alarm is triggered. One
example of use of the generic alarm functions is the detection of gas leaks.
Scheduler
pRack pR300T can manage a generic scheduler which activates a digital
output in certain time bands. Up to 4 daily time bands can be set for each
day of the week. Operation of the generic scheduler can also be linked to
the common scheduler and the output activated based on:
•
summer/winter
•
up to 5 closing periods
•
up to 10 special days
See Paragraph 6.7.2 in the pRack PR300T manual code +0300011EN for
details on the time bands.
48
Page 97 of 169
Regulation variable
Diff.
Regulation variable
Diff.
Fig. 6.ar
Setpoint
Regulation variable
Differential
Differential
Fig. 6.as
P4367 Rev 01
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