17
ENG
“EVD mini” +0300036EN - rel. 1.2 - 23.04.2018
Par.
Description
Def
Min
Max
UOM
Superheat Superheat set point
11(20)
LowSH:
thresh.
55(99)
K
CP
PID: proportional gain
15
0
800
-
ti
PID: integral time
150
0
999
s
5.4 Special
functions
Hot gas bypass by pressure
This function can be used for cooling capacity control. If there is no
request from circuit B, the compressor suction pressure decreases and
the bypass valve opens, so as to deliver more hot gas and decrease circuit
capacity.
E
V1
V2
M
T
E
V1
V2
M
T
S
F
L
CP
C
P
EV
A
B
S1
S2
EVD mini
Key
CP
compressor
V1
solenoid valve
C
condenser
V2
thermostatic expansion valve
L
liquid receiver
EV
electronic valve
F
filter-drier
E
evaporator
S
liquid sightglass
For the wiring see the “General connection diagram”.
This is PID without any protection (LowSH, LOP, MOP, see the chapter
on Protectors), no valve unblock procedure and no auxiliary control
functions. The function uses the hot gas bypass pressure probe read
by input S1, compared against the “Hot gas bypass pressure set point”.
Control is reverse: as the pressure increases, the valve closes and vice-
versa.
Par.
Description
Def
Min
Max
UOM
_P
Hot gas bypass pressure
set point
3
-20(290)
200(2900) bar(psig)
CP
PID: proportional gain
15
0
800
-
ti
PID: integral time
150
0
999
s
Hot gas bypass by temperaturs
This function can be used for cooling capacity control. On a showcase, if
the room temperature probe detects an increase in temperature, cooling
capacity needs to increase, so the valve must close.
E
V1
V2
M
T
S
F
L
EV
CP
C
T
S1
S2
EVD mini
Key
CP
compressor
V1
solenoid valve
C
condenser
V2
thermostatic expansion valve
L
liquid receiver
EV
electronic valve
F
filter-drier
E
evaporator
S
liquid sightglass
For the wiring see the “General connection diagram”.
This is PID without any protection (LowSH, LOP, MOP, see the chapter
on Protectors), no valve unblock procedure and no auxiliary control
functions. The function uses the hot gas bypass temperature probe
read by input S2, compared against the “Hot gas bypass temperature set
point”. Control is reverse: as the temperature increases, the valve closes
and vice-versa.
Par.
Description
Def
Min
Max
UOM
_t
Hot gas bypass tempera-
ture set point
10
-85(-121) 200(392)
°C(°F)
CP
PID: proportional gain
15
0
800
-
ti
PID: integral time
150
0
999
s
5.5 Special control function: smooth lines
Note:
the Smooth_line parameter is only accessible via the
supervisor.
The smooth lines function optimises evaporator capacity based on actual
cooling demand, allowing more effective and stable control. The function
completely eliminates traditional on/off control cycles, modulating the
temperature exclusively using the electronic valve; superheat set point
is controlled through a precise PI control algorithm based on the actual
control temperature.
The master controller (connected via serial to EVD mini), through
dynamic management of the Smooth_line parameter, modifies the
superheat set point for management of the electronic expansion valve,
from a minimum (SH_SET) to a maximum ( Smooth_line): this
consequently acts directly on the PID control algorithm that modifies the
valve position. This is useful when the control temperature approaches
the set point; the Smooth_line parameter is used to prevent the valve
from closing, by reducing the evaporator’s cooling capacity.
In order to use this function, the digital input must be configured as
BACKUP. The Smooth_line parameter thus allows the control set point to
be adjusted instantly.
In the event where there is no network connection, the Smooth_line
parameter is reset so as to resume normal control (START/STOP from
digital input and SH_SET as the superheat set point).
