User manual

44
ENG
MPXPRO - + 0300055EN rel. 1.3 07/03/13
6.5 Control
Minimum and maximum set point values (parameters r1
and r2)
The minimum and maximum value available for the set point can be
defi ned by parameter.
Par. Description Def Min Max UoM
r1 Minimum set point -50 -50 r2 °C/°F
r2 Maximum set point 50 r1 50 °C/°F
Tab. 6.o
ON/OFF (parameter OFF)
The parameter OFF is used to act on the ON/OFF status of the control. A
any digital input confi gured as remote ON/OFF has priority upper respect
to the control from the supervisor or to the parameter OFF.
Par. Description Def Min Max UoM
OFF ON/OFF control
0 = ON; 1 = OFF;
001-
Tab. 6.p
If more than one digital input is selected as ON/OFF, ON status will be
activated when all the digital inputs are closed. The unit is OFF even if
just one of the contacts closes. In this operating mode, the display shows
the standard display, alternating with the message “OFF”. When switching
from ON to OFF and vice-versa, the compressor protector times are
observed.
When OFF, the following are possible:
• access the F, C, A parameters and the set point;
• select the probe to be displayed;
• activate remote ON/OFF;
• display the probe alarms (rE, E1, E2, E3, etc..) and errors EE, EF, Etc, Edc,
alternating with the message OFF.
When OFF, the following alarms are reset:
• high and low temperature;
• open door alarm (dor);
• valve (LSA, LowSH, MOP).
Double thermostat
The double thermostat function is activated by setting parameter rd2>0.
It is used to adapt automatically, that is, without changing the set point
and without an external signal, control of the unit based on a change in
compressor load, especially when switching from day to night and vice-
versa. In fact, at night the showcase curtains are closed, there is less heat
exchange with the surrounding air and the compressor works less.
To do this, two set points and two diff erentials are defi ned:
• St and rd, associated with the outlet probe;
• St2 and rd2, associated with the intake probe.
Par. Description Def Min Max UoM
St2 Intake probe set point with “Double
thermostat”
50 r1 r2 °C/°F
rd2 Diff erential St2 with “Double thermostat”
0.0 = function disabled
0 0 20 °C/°F
Tab. 6.q
The control request occurs when this is active on both probes, as if there
were two thermostats in series. At night the intake probe is controlled
and the outlet probe always signals the request, in the day the outlet
probe is controlled and the intake probe always signals the request.
Sr
Sm
Cooling
Fig. 6.d
Sm
rd
St
ON
R
OFF
Sr
rd2
St2
ON
R
OFF
Fig. 6.e Fig. 6.f
Key
Sm = outlet probe rd = diff erential for St
Sr = intake probe rd2 = diff erential for St2
R = control request
Below is an example of the temperature trend on a vertical showcase
during the day and at night.
night day
Sr
Sm
t
-15...-17 °C
-19...-21 °C
-22 °C-21...-23 °C
-12...-14 °C
-16 °C
Sv=(Sm+Sr)/2
T
Fig. 6.g
Key:
Sm Outlet probe Sv Virtual probe
Sr Intake probe t time
T Temperature
Sm
Sm
Fig. 6.h Fig. 6.i
Key:
Sm Outlet probe
Sr Intake probe
Note:
• if one of the probes has an error or is missing, it is considered as
signalling the request;
• if both probes are faulty or missing, the controller switches to Duty
setting mode: see paragraph 6.6.
Important: if the double thermostat function is activated, the
setting of the following parameters has no eff ect: