46
ENG
mpxone +0300086EN rel. 2.2 - 13.11.2023
Functions
ON/OFF control depends on the capacity of the produce to absorb and release heat, as well as on the evaporator cooling time.
The temperature therefore fl uctuates above and below the set point, and this may cause a decline in the quality of food pres-
ervation. Decreasing the diff erential to make control more precise increases the frequency of solenoid valve opening/closing
cycles.
Setting parameter rC=1 enables reverse operation, suitable for hot cabinet applications.
Minimum and maximum set point values (parameters r1 and r2)
The minimum and maximum value of the set point can be set by parameter.
Code Description Def Min Max UOM User User terminal
r1 Minimum set point -50 -50 r2 °C/°F M NO
r2 Maximum set point 50 r1 200 °C/°F M NO
Night-time operation
During night-time operation the curtain on the display case is closed and consequently less cold inside air is mixed with warm
outside air. The thermal load decreases. The temperature of the air that cools the produce is near the outlet temperature, and
therefore to avoid excessively low temperatures and reduce energy consumption, the set point needs to be increased at night,
by setting parameter r4. Parameter r6 can then be used to assign the virtual probe Sv or intake probe Sr as the control probe.
Naturally, the change to night-time operation must be signalled externally. This is usually done using the curtain switch, set with
parameter DIG, signalling that the curtain has been lowered, or by setting the time bands (parameters tS1 to tS8 and tE1 to tE8),
from the supervisor, or from the main controller via the main/secondary network. To set the time bands, see “Setting the day/
night time bands”.
Code Description Def Min Max UOM User User terminal
r4 Automatic night set point variation 0 -50 50 °C/°F S NO
r6 Night control probe 0/1 = virtual probe Sv/intake probe Sr 0 0 1 - S NO
tS1..8-d Start time band 1 to 8 day: day - see (td1...8-d) 0 0 11 day S NO
tS1..8-hh Start time band 1 to 8 day: hours 0 0 23 hours S NO
tS1..8-mm Start time band 1 to 8 day: minutes 0 0 59 minutes S NO
tE1..8-d End time band 1 to 8 day: day - see (td1...8-d) 0 0 11 day S NO
tE1..8-hh End time band 1 to 8 day: hours 0 0 23 hours S NO
tE1..8-mm End time band 1 to 8 day: minutes 0 0 59 minutes S NO
Notice for HACCP: verify that modifi cation of the night-time set point (parameter /4) is permitted by site HACCP procedures.
If required, obtain the required authorisation and record the changes.
Variable Daytime control
Night-time control
r6 = 0 r6 = 1
Control probe (Sreg) Virtual probe (Sv) Virtual probe (Sv) Intake probe (Sr)
Set point St St+r4
Tab. 5.b
300086_052_R01
t
night
tS1
day
tE1
tS2 tE2 tS8 tE8
Fig. 5.g
During day status:
• Set point = St
• light on
• control on virtual probe Sv
During night status:
• Set point = St + r4
• light off
• control on Sr (if r6=1) or on Sv (if r6=0)
“Weighted control” and “double thermostat” can be used for automatic changeover to night-time operation without an external
signal.
“Weighted control” (or on virtual probe Sv)
This function compensates for the disadvantages of control based solely on the outlet probe or the intake probe. The control
probe becomes the virtual probe:
The weighted average of the outlet and intake probes is used to compensate for the mixing of air from outside the showcase.
Normally the weight of /4 is set to 50% and the value of the virtual probe can be chosen for both display and temperature
recording.
The weighted average of the outlet and intake probes is used to compensate for the mixing of air from outside the showcase.
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