Technical Manual Cold Storage Controller EVP 3150-1 and EVP 3150-2
Page 9
The EVP 3150-2 is able to control one (1) cold sto-
rage with an evaporator equipped with an Electronic
Expansion Valve (EExV).
In such applications, the EExV takes over the
jobs of the former solenoid valve and the com-
pulsive thermal expansion valve.
Expansion Valves
The EVP is able to drive
pulse-width modulated,
cycling expansion valves
and
valves with ther-
mal drive
.
AC or DC type valves can be used, they are supplied
by mains voltage via SSR-relay with 2 outputs.
Missmatches valve/nozzle and evaporator will be
compensated in a wide range. Because the valves
need no high pressure difference to open, it's possible
to work with low condensation pressures, as long
as the configuration allows that.
From this it follows a higher COP-value for the
compressor and so an option for energy saving. The
energy saving depends on outdoor temperature (if
the condenser is located on the roof) and is higher
in winter than in summer.
By the optimal filling of the evaporator and the more
equable icing an additional energy saving of 2 - 5%
is possible.
Measuring Methods
The EVP is able to work with 2 measuring
methods:
1. Pressure Transmitter and Temperature Sensor
at the evaporator outlet, this is equivalent to the
arrangement of a thermal expansion valve.
2. 2 Temperature Sensors at the inlet and the
outlet of the evaporator.
The unit always controls the 'virtual' aperture
size of the valve to reach an optimal filling
and so the optimal efficiency ratio of the
evaporator. Period time and pulse-width of
the PWM-control are defined by the control algorithm
(autoadaptive), disturbances like suction pressure
fluctuations and flashgas will be filtered out.
1. Pressure / Temperature method
To capture the superheat, a pressure transmitter with
2-10V output signal and a TF 501 temperature sensor
at the evaporators outlet is used. The arrangement
of this parts is equivalent to the components of a
thermal expansion valve.
This method is strongly recommended
for single machines or plants with just a
few evaporators. The compressor can
be controlled by an external suction
pressure switch or the cooling relay of the EVP.
By this, special operating modes and an auto-
matic "pumpdown" function are possible.
Variable Overheat Control
If you get a difference by the settings of
P60
(Su-
perheat, minimum value) und
P65
(Superheat,
maximum value), then the superheat will be
shifted by the control algorithm within the ON-
point (shysteresis
r10
) and the OFF-point
(setpoint). If the function is disabled, the superheat
value is determined by
P60
only.
Function is disabled:
P65
(Superheat, maximum value) exceeds
P60
.
Function enabled:
P65
is below or equal to
P60
.
Temperature control with Electronic Expansion Valves
Sensor Positions
Pressure Transmitter/
Temperatur Sensor method
2 Temperature Sensors method
Parameterization
The following recommendations refer to the pressure
transmitter "DG -1/9 2-10V".
L05
...........Display of the temperature which is
calculated from pressure value and
refrigerant
L09
...........Actual Overheat Value
P55
...........Method is active as soon as the used
refrigerant is selected.
P53
..........Lower limit of transmitter
(-1.0, relative pressure)
P54
..........Upper limit of transmitter
(+9.0, relative pressure)
P56
..........Lower voltage limit of the pressure
transmitter input. (2V. Below this 2V,
an error message is generated).
P57
..........Upper voltage limit of the pressure
transmitter input (10V).
P60
...........Superheat setpoint, minimum value
(depends on evaporator)
P61
...........MOP-setpoint (Maximum Opening
Pressure, i.e. limitation of the
evaporation temperature at the outlet.
Depends on compressor resp. plant).
P65
...........Superheat setpoint, maximum value
The settings of
P60/P61
depend on the used com-
pressor and the used evaporator.
P62
...........P-Part of the Expansion Valve Control
P63
...........I-Part of the Expansion Valve Control
The factory settings of P62/P63 are almost ideal for
all kind of cold storages, changes must be made
with care.
After this basic settings, all other relevant parameters
must be set.
2. Temperature sensor method
To capture the superheat, 2 temperature sensors
(TF 501) are used, one at the inlet and one at the
outlet of the evaporator. For this method, no pressure
information is necessary.
Parameterization
P55
......Must be set to 0, i.e. no refrigerant
selected. Inlet- and outlet sensor must be
assigned. No further parameterizing
necessary, except standard settings.
Limitation of the EEx-Valve Signal
With this function (
P66
) the maximum opening of
oversized expansion valves can be limited. It affects
on all possible expansion valve output signals:
- Analogue output assigned to an EEx-Valve
- Expansion valve relay
Actuating Variable Delay for EEx-Valves
P67
(setep size) and
P68
(output delay) affect as
actuating variable delay for the Electronic Expan-
sion Valve, both for the analogue output as well as
the relay output. The OFF-value (0%) will be in-
itiated immediately with:
- Controller OFF
- Defrost initiation
Information
Parameter "
L42
" (Actual Values Page) shows the
state of the EEx-valve permanently.
P
defrost heater
evaporator sensor
(defrost limitation)
control sensor
at air inlet
(room sensor)
EExp. Valve
Druck-
geber
Outlet-
sensor
further evaporators
defrost heater
evaporator sensor
(defrost limitation)
EExp. Valve
Outlet-
sensor
Intlet-
sensor
control sensor
at air inlet
(room sensor)
