Carel MPXPRO User Manual page 53

Key
T_EVAP Evaporation temperature
MOP MOP protection
ALARM Alarm
PM1 represents the maximum evaporation pressure, expressed in
degrees (saturated), above which the MOP protection and alarm are
activated (each with its own delay times). There is a gradual return to
normal operation, to avoid the critical situations arising again.
PM2 represents the integration time for the maximum evaporation
pressure protection function. This replaces the normal PID control during
MOP status.
PM2 = 0 ==> MOP protection and alarm disabled
PM3 represents the alarm activation delay after exceeding the MOP
threshold. When the alarm is activated, the following occur:
• Message 'MOP' shown on the display
• The buzzer is activated
The alarm features automatic reset when the evaporation pressure falls
below the threshold PM1.
PM4 = 0 ==> MOP alarm disabled
PM4 represents the activation delay MOP protection after the last
activation of the solenoid valve.
PM5 allows the local or network solenoid valve (if available), based on
the confi guration of the system (see parameter r7), to be closed upon
activation of the MOP alarm. If the expansion valve (0 steps) is closed
completely during MOP status (before the activation of the alarm), the
solenoid valve confi gured is also closed.
LSA - Low suction temperature
When the suction temperature falls below the threshold, the alarm is
activated after the set delay, closing the electronic valve or the local and/
or shared tLAN solenoid valve (if available). The alarm is reset when the
suction temperature exceeds the set threshold plus the hysteresis. Reset
is automatic for a maximum of four times in a two hour period. Upon the
fi fth activation in such period, the alarm is saved and requires manual
reset from the user terminal or supervisor.
Par. Description
P11 LSA: low suction temperature threshold
P12 LSA: alarm delay
0 = alarm disabled
P13 LSA: alarm diff erential (°C)
0 = reset always automatic
P10 Enable close solenoid valve (optional) for
low superheat (LowSH) and/or low suction
temperature (LSA)
P11 represents the suction temperature below which the alarm is
activated, after the corresponding delay. The threshold for resetting the
alarm is represented by this threshold plus the hysteresis P13.
P12 represents the alarm activation delay after exceeding the threshold
P11. When the alarm is activated, the following occur:
• message 'LSA' shown on the display;
• the buzzer is activated
The alarm features automatic reset for the fi rst four activations over a two
hour period, then becomes manual reset.
P12 = 0 ==> LSA alarm disabled
P13 represents the hysteresis used to deactivate the LSA alarm.
P13 = 0 ==> reset always automatic.
P10 allows the network solenoid valve to be closed in the event of low
superheat (LowSH) and/or low suction temperature alarm (LSA).
• P10=1 (default): the unit that signals the LowSH and/or LSA status,
as well as closing the local solenoid valve, propagates the request
across the local network (LAN). This enables propagation of the closing
request over the tLAN network to the Master.
To eff ectively close the network solenoid valve (if available)(P10=1), the
solenoid on the Master must be enabled as a network valve (parameter
r7=1), the only type that can accept network requests.
PM1 MOP threshold
PM3 Alarm delay
t Time
Def Min Max UoM
-45.0 -50.0 50.0 °C/°F
600 0 999 s
10.0 0.0 60.0 °C/°F
0 0 1 -
Tab. 6.j.c
53
• P10=0: the unit that signals the LowSH and/or LSA status does not
enable the closing of the network and local solenoid valve.
T_SUCT
P11+P13
P11
ON
LSA
OFF
ON
ALARM
OFF
P12
Key
T_SUCT Suction temperature
LSA: low suction temperature
P11
threshold
P12 LSA: alarm delay
LOP Minimum evaporation pressure
Function useful above all for stand-alone refrigeration controllers, used to
prevent the evaporation pressure from remaining excessively low for too
long. When the evaporation pressure, expressed in degrees (saturated),
falls below the threshold, the LOP protection is activated, which adds an
integration action to normal PID control, specifi cally devised to be more
reactive as regards the opening of the valve. The PID control remains
active, as the superheat must continue to be monitored as to avoid
fl ooding the compressors. The LOP alarm is delayed from the activation of
the protection function, both are reset automatically when the pressure
value, in degrees (saturated), exceeds the threshold.
T_EVAP
PL1
ON
LOP
OFF
ON
ALARM
OFF
PL3
Key
T_EVAP Evaporation temperature
LOP LOP protection
ALARM Alarm
Par. Description
PL1 LOP: minimum saturated evaporation
temperature threshold
PL2 LOP: integration time
PL3 LOP: alarm delay
0 = alarm disabled
PL1 represents the evaporation pressure, expressed in degrees
(saturated), below which the LOP protection is activated. The protection
is deactivated immediately when the pressure exceeds this threshold.
PL2 represents the integration constant used during the activation of
the LOP protection. This integration time acts in parallel to normal PID
control.
PL2 = 0 ==> LOP protection and alarm disabled
ENG
t
t
t
Fig. 6.u
P13 LSA: Alarm diff erential
t time
LSA LSA protection
t
t
t
Fig. 6.v
PL1 LOP: threshold
PL3 LOP : alarm delay
t Time
Def Min Max
-50.0 -50.0 50.0
0.0 0.0 240.0
0 0 240
Tab. 6.j.d
MPXPRO - + 0300055EN rel. 1.1 30/08/10
UoM
°C/°F
s
s