Carel Clima User Manual download pdf (Page 42)

42 “MPXPRO” +030220186 - rel. 1.0 - 22.05.2007

Cooling

Fig. 6.d

E N G L I S H

Examples of using parameter ‘ro’:

Examples of using ‘ro’ in the

event of a probe fault

New

probe

Control probe Set point ro=(Sr-Sm) New set point

E.g. 1 Sm fault in daytime

operation

Sr Sv

/4=0

100% Sm

St=-2 5 = +2-(-3) =St+ro*(100-/4)/100

=-2+5*(100-0)/100

E.g. 2 Sr fault in daytime

operation

Sm Sv

/4=75

75% Sm

St=-1 5=+2-(-3) =St-ro*(100-/4)/100

=-1-5*(100-75)/100

= -2.25

Tab. 6.d

6.2.3 Special functions

This paragraph describes the following advanced control functions on MPXPRO:

6.2.3.1 Double Thermostat

6.2.3.2 Duty Setting

6.2.3.3 Continuous cycle

6.2.3.1 Double Thermostat

Double Thermostat is a special function on MPXPRO that is used to control the temperature inside a that is used to control the temperature inside a

refrigeration unit using two separate thermostats, one associated with the outlet probe and the other with

the intake probe. This control technique is used to appropriately manage the day-night changeover, and

in particular the closing of the curtain at night, without requiring any external contact. The lowering of the

curtain in fact generally causes a decrease in the temperature inside the unit, and may cause problems if

the control method is not adapted.

The two thermostats each have their own speciﬁc set point (St for the outlet probe, St2 for the intake

probe) and corresponding differential (rd for Sm, rd2 for Sr.

Probe set point Differential

outlet ‘Sm’ ‘St’ ‘Rd’

intake ‘Sr’ ‘St2’ ‘Rd2’

The operation of each thermostat (Sm or Sr) is perfectly identical to the operation described for the main

control probe.

The general control status depends on the combination of the status of both thermostats, that is, control

will be active only when both thermostats require refrigeration. The table below illustrates the general

status of the unit based on the status of the two thermostats.

Outlet probe Sm Intake probe Sr Thermostat

call call ON

satisﬁed call OFF

call satisﬁed OFF

satisﬁed satisﬁed OFF

error or absent (equivalent to call) call ON

error or absent (equivalent to call) satisﬁed OFF

call error or absent (equivalent to call) ON

satisﬁed error or absent (equivalent to call) OFF

error or absent error or absent duty setting ‘c4’

Tab. 6.e

Note:

Parameter ‘rd2’>0 enables the double thermostat function.double thermostat function.

In double thermostat operating mode, there is no recovery from outlet and intake probe errors using

parameter ‘ro’.

In double thermostat operating mode, there is no change in the set point in night-time operation, with

reference to parameter ‘r4’.

Below are the values of parameters St2 (intake probe set point Sr) and rd2 (intake probe set point diffe-

rential) required to activate the double thermostat function.

St2 Intake probe set point with ‘double thermostat’

Code UOM Min Max Def.

St2

°C/°F r1 r2 50.0

In the Double Thermostat function, this indicates the value of the set point in relation to the intake probe

(Sr).

rd2 Control differential with ‘double thermostat’

Code UOM Min Max Def.

rd2

°C/°F 0.0 20.0 0.0

This represents the differential for the intake probe Sr in mode Double Thermostat mode.

rd2=0 the ‘double thermostat’ function is disabled.

6.2.3.2 Duty Setting

Duty Setting is a special function used to maintain control in emergency situations with errors in the tem-

perature control probes. The controller, in fact, even with just one temperature control probe operating

(outlet or intake), attempts to adapt its operating characteristics to the special conditions (see parameter

ro). If neither of the two is available, the “Duty Setting” control starts. With this function, the controller

is activated at regular intervals, operating for a time equal to the value set for the duty setting parameter

(c4) and off for a ﬁxed time of 15 minutes. This mode manages to temporarily extend service times.

•

see paragraph 5.2 “Basic control”, p. 27see paragraph 5.2 “Basic control”, p. 27

B@ r4: Automatic night-time set point variation, p. 28B@ r4: Automatic night-time set point variation, p. 28

A@ ro: Control offset with probe error, p. 28A@ ro: Control offset with probe error, p. 28

B@ St, rd: Unit set point - temperature differential, p. 27

1 2 ... 37 38 39 40 41 42 43 44 45 46 47 ... 71 72

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