28
ENG
“EVD mini” +0300036EN - rel. 1.2 - 23.04.2018
t
t
t
t
O
FF
ON
R
O
FF
ON
P
O
FF
ON
S
O
FF
ON
A
T1
W
Fig. 8.o
Key:
A
Control request
T1 Pre-positioning time
P
Pre-positioning
W
Wait (wait)
S
Standby
t
Time
R
Control
Positioning (change cooling capacity)
This control status is only valid for controllers connected to the pCO
via RS485. If there is a change in unit cooling capacity of at least 10%,
sent from the pCO via RS485, the valve is positioned proportionally. In
practice, this involves repositioning starting from the current position in
proportion to how much the cooling capacity of the unit has increased or
decreased in percentage terms. When the calculated position has been
reached, regardless of the time taken, there is a constant 5 second delay
before the actual control phase starts.
Note:
if information is not available on the variation in unit cooling
capacity, this will always be considered as operating at 100% and therefore
the procedure will never be used. In this case, the PID control must be
more reactive (see the chapter on Control) so as to react promptly to
variations in load that are not communicated to the driver.
t
t
t
t
OFF
ON
R
OFF
ON
NP
OFF
ON
C
OFF
ON
A
T3
W
Fig. 8.p
Key:
A
Control request
R
Control
C
Change in capacity
T3 Repositioning time
NP
Repositioning
t
Time
W
Wait
S
top/end control
The stop procedure involves closing the valve from the current position
until reaching 0 steps, plus a further number of steps so as to guarantee
complete closing. Following the stop phase, the valve returns to standby.
t
t
t
t
OFF
ON
R
OFF
ON
ST
OFF
ON
S
OFF
ON
A
T4
Fig. 8.q
Key:
A
Control request
R
Control
S
Standby
T4 Stop position time
ST
Stop
t
Time
8.10 Special control states
As well as normal control status, the driver can have three special states
related to specific functions:
•
manual positioning: this is used to interrupt control so as to move the
valve, setting the desired position;
•
recover physical valve position: recover physical valve steps when fully
opened or closed;
•
unblock valve: forced valve movement if the driver considers it to be
blocked.
Manual positioning
Manual positioning can be activated at any time during the standby or
control phase. Manual positioning, once enabled, is used to freely set the
position of the valve using the corresponding parameter.
Control is placed on hold, all the system and control alarms are enabled,
however neither control nor the protectors can be activated. Manual
positioning thus has priority over any driver state/protector.
Par. Description
Def.
Min.
Max. UoM
U1 Enable manual valve positioning:
0/1=yes/no
0
0
1
-
U2 Manual valve position
0
0
999
step
Notes:
1.
the manual positioning status is NOT saved when restarting after a
power failure.
2.
in for any reason the valve needs to be kept stationary after a power
failure, proceed as follows:
•
remove the valve stator;
•
set the PID proportional gain =0. The valve will remain stopped at
the initial opening position, set by corresponding parameter