29
ENG
“EVD mini” +0300036EN - rel. 1.2 - 23.04.2018
R
etrieve physical valve position
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.
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.
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 do 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;
•
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.
