Carel MPXone - Page 49

49
ENG
mpxone +0300086EN rel. 2.2 - 13.11.2023
Functions
Sm
Sr
300086_007_R01
Sr = - 12 to -14°C, St = -16°C
Sm
Sr
300086_008_R01
Sr = - 17 to -15°C, St = -16°C
Ref. Description
Sm outlet probe
Sr intake probe
Fig. 5.m Fig. 5.n
Notice:
• if one probe is faulty or missing, the corresponding request will be active;
• if both probes are faulty or missing, the controller switches to duty setting mode.
Caution: if the double thermostat function is activated, the setting of the following parameters has no eff ect:
• r6 (night-time control probe);
• r4 (automatic night-time set point variation).
Control off set with probe error (parameter ro)
Code Description Def Min Max UOM User User terminal
ro Control off set with probe error 0 0 20 °C/°F S NO
MPXone in standard mode uses the virtual probe Sv for control, that is, the weighted average of the outlet and intake probe
(see parameter /4). If one of the two probes making up the virtual probe is broken or has an error, parameter ro is used to con-
tinue normal control in controlled conditions, without the need for immediate intervention by maintenance personnel. The
recommended value of ro is the temperature diff erence between the outlet probe and intake probe reading in steady operating
conditions of the refrigeration unit:
The following cases may occur:
• outlet probe Sm error: MPXone starts control based on the intake probe Sr alone, considering a new set point (St*) determined
by the formula:
• intake probe Sr error: MPXone starts control based on the outlet probe Sm alone, considering a new set point (St*) determined
by the formula:
If night-time operation has been set with the intake probe as the control probe, the controller considers /4=100 and uses the
outlet probe. The new set point becomes:
Notice:
• if ro=0 the function is not active;
• for night-time operation the new set point is added to the value defi ned by r4 (= automatic night-time set point variation);
• in the event of errors on both probes, the controller switches to duty setting operation.
Example
Sm fault in daytime operation, with /4=50, St=-4, Sr=0, Sm=-8, ro (recommended) = 0-(-8) = 8. Then the new control probe will
be Sr with:
St*= -4+8 •(100-50)/100=0.