User manual

ManualsBrandsCarel ManualsMusical equipmentMPXPRO

ENG

MPXPRO - + 0300055EN rel. 1.3 07/03/13

independently from normal temperature control. When there is a

refrigeration call (the compressor / solenoid valve relay is activated),

control of the electronic valve is also activated and then managed

independently. If the superheat value read by the probes is greater

than the set point, the valve is opened proportionally to the diﬀ erence

between the values. The speed of variation and the percentage of

opening depend on the PID parameters set. The opening is continuously

modulated based on the superheat value, with PID control.

Note: all the references relating to control of the electronic valve

are based on the use of a CAREL E

V electronic expansion valve.

The descriptions are then made considering the steps of the stepper

motor used for this type of valve, for example, the maximum number of

opening steps is 480. All the functions are also then described for PWM

valves. In particular, instead of the maximum opening expressed as the

number of steps, the maximum ON/OFF time of the PWM valve is

considered (default 6 seconds). The absolute openings expressed as

steps must then be suitably converted by the user and referred to the

maximum ﬁ xed period, expressed in seconds.

Apertura valvola/Valve opening

Surriscaldamento/Superheat

Fig. 6.o

Type of refrigerant (parameter PH)

This is used to set the type of gas refrigerant used in the system. The table

below shows the types of gas possible and the associated PH values.

For compatibility with the E

V valve see paragraph 4.3. Contact CAREL if

installing E

V valves in systems that use refrigerants not listed in the table.

Par. Description Def Min Max UoM

PH Type of refrigerant

1 = R22 10 = R717 19 = R407A

2 = R134a 11 = R744 20 = R427A

3 = R404A 12 = R728 21 = R245Fa

4 = R407C 13 = R1270 22 = R407F

5 = R410A 14 = R417A

6 = R507A 15 = R422D

7 = R290 16 = R413A

8 = R600 17 = R422A

9 = R600a 18 = R423A

3 1 22 -

Tab. 6.an

Important: if the type of refrigerant is not correct, there may be

return of liquid to the compressor.

Electronic valve (parameter P1)

MPXPRO can control two diﬀ erent models of electronic expansion valve,

each with the speciﬁ c type of optional expansion board. Parameter P1 is

used to set the model installed:

Par. Description Def Min Max UoM

P1 Electronic valve

0 = not used, 1 = PWM valve

2 = CAREL E

V valve

002-

Tab. 6.ao

Superheat set point (parameter P3)

This is used to set the reference superheat value for the control of the

electronic valve. It does not determine the actual superheat value, but

rather the desired value. MPXPRO, with PID control, tends to maintain the

actual superheat, calculated based on the probe readings, around the

value set for this parameter. This is done by gradually varying the opening

of the valve based on the diﬀ erence between the actual superheat and

the set point.

Important: the set point value calculated depends on the quality

of the installation, the position of the probes and other factors.

Consequently, depending on the installation the set point read

may deviate from the actual value. Set point values that are too low (2 to

4 K), albeit ideally usable, may cause problems involving the return of

liquid refrigerant to the compressor rack.

Par. Description Def Min Max UoM

P3 Superheat set point 10.0 0.0 25.0 K

Tab. 6.ap

Initial valve position when control starts (par. cP1)

This is used to set the position of the valve as a percentage when

control starts. High values ensure intense and immediate cooling of the

evaporator when each call is sent, however may cause problems if the

valve is oversized with reference to the cooling capacity of the controller.

Low values, on the other hand, allow a more gradual and slower action.

Par. Description Def Min Max UoM

cP1 Initial valve position when control starts 30 0 100 %

Tab. 6.aq

Initial valve position maintenance time after defrost

(parameter Pdd)

At the end of a defrost, during the dripping phase, the expansion valve

can be forced open to the initial value set for cP1 for a time equal to

Pdd. This means greater immunity of the unit to return of liquid to the

compressor rack due to an excessively high evaporator temperature.

Par. Description Def Min Max UoM

Pdd Initial valve position maintenance time

after defrost

10 0 30 min

Tab. 6.ar

Valve standby position (parameter PSb)

This indicates the position, as the absolute number of steps, that the

valve must move to after having completely closed, to restore the elastic

operating conditions of the valve spring, by releasing the compression

(for stepper valve only).

Note: the value of this parameter represents the absolute position

of the valve during the closing phase (value read using the

advanced parameter PF on the supervisor).

Par. Description Def Min Max UoM

PSb Valve standby position 0 0 400 step

Tab. 6.as

Enable fast update of the valve parameters to supervisor

(parameter Phr)

This is used to enable the fast update to the supervisor of the variables

relating to the electronic expansion valve, such as:

• PF: absolute position in number of steps (stepper valve only);

• SH: superheat;

• PPV: position as a percentage;

• tGS: superheated gas temperature;

• tEu: saturated evaporation temperature;

Useful in the commissioning phase or start-up:

Phr = 0: fast update disabled (update every 30 s);