Control - Carel MPXPRO User Manual

ENG

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
r1 Minimum set point
r2 Maximum set point
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
OFF ON/OFF control
0 = ON; 1 = OFF;
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
St2 Intake probe set point with "Double
thermostat"
rd2 Diff erential St2 with "Double thermostat"
0.0 = function disabled
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.
MPXPRO - + 0300055EN rel. 1.0 30/08/10
Def Min Max
-50 -50 r2
50 r1 50
Tab. 6.e.a
Def Min Max
0 0 1
Tab. 6.e.b
Def Min Max
50 r1 r2
0 0 20
Tab. 6.e.c
Sr
Sm
Cooling
Fig. 6.d
R
ON
OFF
UoM
°C/°F
rd
°C/°F
St
Fig. 6.d
Key
Sm = outlet probe
Sr = intake probe
R = control request
UoM
-
Below is an example of the temperature trend on a vertical showcase
during the day and at night.
T
-15...-17 °C
Sv=(Sm+Sr)/2
-19...-21 °C
-22 °C
Key:
Sm Outlet probe
Sr Intake probe
T Temperature
NIGHT: Sm= -19...-21 °C
Set point = -22 °C
Sm
UoM
°C/°F
Sr
°C/°F
Sr= -15...-17 °C
Set point = -16 °C
Fig. 6.g
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.
44
R
ON
OFF
Sm
rd2
St2
Fig. 6.e
rd = diff erential for St
rd2 = diff erential for St2
night day
Sr
Sm
Fig. 6.f
Sv Virtual probe
t time
DAY: Sm= -21...-23 °C
Set point = -22 °C
Sm
Sr
Sr= -12...-14 °C
Set point = -16 °C
Fig. 6.h
Sr
-12...-14 °C
-16 °C
-21...-23 °C
t