l
The superheat set point for managing the electronic expansion valve can vary between a minimum
(traditional set point P3) and maximum limit (P3 + PHS: max. offset) using PI control (pre-configured),
based on the control temperature and how far this is from the corresponding set point St;
l
The temperature inside the showcase can fall slightly below the set point St, without stopping the
main control, however simply closing the electronic valve;
l
Temperature control (and consequently the solenoid valve relay) therefore remains active at all times,
while the electronic expansion valve stops the flow of refrigerant into the evaporator;
l
It is easy to use, as it is the controller itself that automatically adapts control based on current
operation, without requiring special parameter settings;
The main effects are:
l
No swings in temperature and superheat due to the set point being reached;
l
Stable temperature and superheat control;
l
Maximum energy savings due to load stabilisation.
l
Lower dehumidification effect and stable air temperature around the food.
Fig.5.ab
Code Description
Def Min Max UOM User
User
terminal
PSM
Smooth Lines - enable function
0
0
1
-
S
NO
PLt
Smooth Lines - offset to stop control below set point
2
0
10 °C/°F
S
NO
PHS
Smooth Lines - max superheat offset
15
0
50
K
S
NO
Note:
Smooth Lines is not compatible with traditional Floating Suction control, and must be used
with the new Rack Smart Set algorithm.
5.6.1 Protection functions
LowSH: low superheat threshold (par. P7)
To prevent too low superheat values that may cause the return of liquid to the compressor or system
instability (swings), a low superheat threshold can be defined, below which a special protection function
is activated. The LowSH threshold must be lower than the superheat set point. When the superheat falls
below the threshold, the system immediately enters low superheat status and activates an integral
control action, with the aim of closing the electronic valve more quickly. The low superheat integral time
indicates the intensity of the reaction: the lower the value, the more intense the reaction will be. In
practice, the intensity of the system’s “reaction” is increased. If the device remains in low superheat status
for a certain period, a low superheat alarm is activated, with the display showing the message ‘LSH’, if
enabled. The low superheat signal features automatic reset, when the condition is no longer present or
the controller is switched off (standby). When low superheat status is activated, the local solenoid valve
can be forced closed (parameter P10).
Code Description
Def Min Max UOM User
User
terminal
P7
LowSH: low superheat threshold
7 -10 P3
K
S
YES
P8
LowSH: integral time
0 = function disabled
15
0 240
s
M
NO
ENG
0300086EN rel. 1.0 – 04.09.2018
5. Functions |
77
Содержание MPXone ACS00CB000010
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