User manual

49
ENG
MPXPRO - + 0300055EN rel. 1.3 07/03/13
6.8 Evaporator fans
See paragraph 5.7. The advanced parameters for the evaporator fans
concern the minimum and speed maximum, the selection of the type
of motor (inductive or capacitive) and the setting of the start-up time.
Par. Description Def Min Max UoM
F6 Maximum fan speed 100 F7 100 %
F7 Minimum fan speed 0 0 F6 %
F8 Fan peak time
0 = function disabled
0 0 240 s
F9 Select fan control with output PWM1/2
(with phase cutting speed control)
0 = by pulse; 1 = by duration
101-
F10 Evaporator fan forcing time at maximum
speed
0 = function disabled
0 0 240 min
Tab. 6.al
F6: is the maximum fan speed, expressed as a % of the output. For 0 to
10 V outputs, it represents the output voltage at maximum speed as
a percentage. For phase control outputs, it represents the maximum
portion of the semi-wave applied to the load as a percentage. The same
is true for the minimum speed set for F7. The fan peak time F8 represents
the operating time at maximum speed set using parameter F6 to
overcome the mechanical inertia of the motor. F10 represents the time
the fan is operated at maximum speed for the peak time (F8).
If the fan is operated for too long at a reduced speed, ice can form on the
blades. To avoid this, at intervals of F10 minutes, the fan is forced to the
maximum speed for the time expressed by the parameter F8.
If the evaporator fan speed is controlled with phase control, F9 determines
the type of control:
F9=0: by pulse, for capacitive motors;
F9=1: by duration, for inductive motors.
See paragraph 5.7 for the meaning of parameters F5, F1, Frd.
F5+1
F5
F1
t
FAN
SPEED
0%
F7
F6
F1-Frd
Fig. 6.n
6.9 Electronic valve
The stepper electronic valve requires a power supply to be able to open
or close.
Starting from version 2.8, MPXPRO features a special ultracap to guarantee
the power required to close the electronic valve in the event of power
failures. Further details on installing and selecting the cable are shown in
the section on connections and wiring diagrams.
The ultracap takes around 2 minutes to charge completely when
completely discharged. It is therefore recommended to set a delay time
no less than 2 minutes for compressor and evaporator fans enabling in
power-up (parameter c0).
Introduction
MPXPRO, depending on the optional cards installed, can manage
diff erent types of electronic expansion valve. Specifi cally:
Driver Code Model of valve
stepper MX3OPSTP* CAREL E
2
V
PWM MX3OPPWM**
PWM 115 to 230 Vac
PWM 110 to 230 Vdc
Tab. 6.am
To manage the electronic expansion valve, two additional probes must
be installed and suitably confi gured:
• temperature probe for measuring the superheated gas temperature at
the evaporator outlet.
• pressure probe for the measurement of the saturated evaporation
pressure / temperature at the evaporator outlet.
Installation notes:
MPXPRO is designed to manage one electronic expansion valve that
controls the fl ow of refrigerant inside an individual evaporator. Two
evaporators in parallel cannot be managed with just one electronic
expansion valve.
• The NTC/PTC/PT1000/NTCL243 temperature probe must be installed
near the evaporator outlet, according to the standard installation
methods (see the installation notes on the E
2
V instruction sheet).
Suitable thermal insulation is recommended. CAREL off ers special
types of probes designed to simplify installation in contact with the
refrigerant pipe:
– NTC030HF01 for Retail use IP67, 3m, -50T90 °C, 10 pcs
– NTC060HF01 for Retail use IP67, 6m, -50T90 °C, 10 pcs
To measure the saturated evaporation temperature, diff erent types
of probes can be used; in particular, the following can be confi gured
(advanced parameter /FE):
• 0 to 5 V ratiometric pressure probe (recommended by CAREL);
• NTC/PTC/PT1000 temperature probe;
• 4 to 20 mA active pressure probes (powered externally).
MPXPRO can measure the saturated evaporation temperature using a
normal NTC/PTC/PT1000/NTCL243 temperature probe (see price list). This
solution, even if economically convenient, requires careful installation
and in any case does not off er the same precision as a ratiometric
probe. CAREL recommends the use of ratiometric probes for reading the
evaporation pressure, which is automatically converted to the saturated
temperature using the specifi c tables for the type of refrigerant used.
Description of operation
The values read by the probes described above are called:
• tGS = superheated gas temperature;
• tEu = saturated evaporation temperature converted from pressure
These values are used to calculate the superheat:
• SH = tGS - tEu
MPXPRO manages the proportional opening of the electronic expansion
valve, adjusting the fl ow of refrigerant in the evaporator, so as to maintain
the superheat around the value set for advanced parameter P3 (superheat
set point). The opening of the valve is controlled simultaneously yet