27
ENG
“EVD evolution” +030222041 - rel. 1.0 - 01.06.2008
Recover physical valve position
Parameter/description
Def.
Min.
Max. UOM
Valve
Synchronise valve position in opening
1
0
1
-
Synchronise valve position in closing
1
0
1
-
Tab. 6.l
This procedure is necessary as the stepper motor intrinsically tends to lose
steps during movement. Given that the control phase may last continuously
for several hours, it is probable that from a certain time on the estimated
position sent by the valve driver does not correspond exactly to the physical
position of the movable element. This means that when the driver reaches
the estimated fully closed or fully open position, the valve may physically
not be in that position. The “Synchronisation” procedure allows the driver to
perform a certain number of steps in the suitable direction to realign the
valve when fully opened or closed.
Note:
realignment is in intrinsic part of the forced closing procedure and is
•
activated whenever the driver is stopped/started and in the standby
phase;
the possibility to enable or disable the synchronisation procedure
•
depends on the mechanics of the valve. When the setting the “valve”
parameter, the two synchronisation parameters are automatically
defined. The default values should not be changed.
Unblock valve
This procedure is only valid when the driver is performing superheat control.
Unblock valve is an automatic safety procedure that attempts to unblock a
valve that is supposedly blocked based on the control variables (superheat,
valve position). The unblock procedure may or may not succeed depending
on the extent of the mechanical problem with the valve. If for 10 minutes the
conditions are such as to assume the valve is blocked, the procedure is run a
maximum of 5 times. The symptoms of a blocked valve doe not necessarily
mean a mechanical blockage. They may also represent other situations:
mechanical blockage of the solenoid valve upstream of the electronic
•
valve (if installed);
electrical damage to the solenoid valve upstream of the electronic
•
valve;
blockage of the filter upstream of the electronic valve (if installed);
•
electrical problems with the electronic valve motor;
•
electrical problems in the driver-valve connection cables;
•
incorrect driver-valve electrical connection;
•
electronic problems with the valve control driver;
•
secondary fluid evaporator fan/pump malfunction;
•
insufficient refrigerant in the refrigerant circuit;
•
refrigerant leaks;
•
lack of subcooling in the condenser;
•
electrical/mechanical problems with the compressor;
•
processing residues or moisture in the refrigerant circuit.
•
Note:
the valve unblock procedure is nonetheless performed in
each of these cases, given that it does not cause mechanical or control
problems. Therefore, also check these possible causes before replacing
the valve.
