46
ENG
Hecu CO
2
+0300085EN rel. 2.2 - 07.05.2019
LowSH Low superheat protection.
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 defi ned, below which a special protection function is activated.
When the superheat falls below the threshold, the system immediately
enters low superheat status and activates an integral control action, which
added to normal control is aimed at closing the electronic valve more
quickly. 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, any local solenoid valves can be
forced closed (parameter P10).
Par. Description Def Min Max UOM
P7 LowSH: low superheat threshold 7.0 -10.0 P3 K
P8 LowSH: integral time
0 = function disabled
15.0 0.0 240.0 s
P9 LowSH: alarm delay
0 = alarm disabled
600 0 999 s
Tab. 7.c
t
B
P9
t
t
ON
P7
LowSH
SH
OFF
ON
ALARM
OFF
Fig. 7.p
Key
SH Superheat P7
LowSH protection
threshold
LowSH Low superheat protection P9 Alarm delay
ALARM Alarm t time
Defrosting evaporators connected via serial line
The purpose of this function is to prevent the compressor from starting
when one or more evaporators are defrosting. When the compressor
stops (due to control, alarm, ...) if the "available" capacity is higher than
the threshold (% of total capacity), the compressor can start normally,
otherwise it stays off until the evaporators fi nish defrosting or the suction
pressure is higher than a settable safety threshold.
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