Application guidelines
46
FRCC.PC.014.A4.22
Installation
Vacuum pump down and
moisture removal
Refrigerant charging
Moisture obstructs the proper functioning
of both the compressor and the refrigeration
system. Air and moisture reduce service life and
increase condensation pressure, which causes
abnormally high discharge temperatures that
are then capable of degrading the lubricating
properties of the oil. The risk of acid formation
is also increased by air and moisture, and this
condition can also lead to copper plating. All
these phenomena may cause both mechanical
and electrical compressor failures. The typical
method for avoiding such problems is a vacuum
pump-down executed with a vacuum pump, thus
creating a minimum vacuum of 500 microns (0.67
mbar). Please refer to News bulletin “Vacuum
pump down and dehydration procedure”.
Air-conditioning installations exist in a multi-
ple of designs and with many possible system
components installed. The system design and
the presence or absence of certain components,
not only influence the system behaviour during
operations; they can also be of a great influence
during the refrigerant charging procedure.
Improper charging procedure could cause com-
pressor damage in several ways excessive LP/HP
pressure differences, liquid slugging or vacuum
operation. The below charge procedure is strong-
ly recommended to reduce these risks.
• Prior to refrigerant charging a system
vacuum and moisture removal procedure
must have been carried out. (See previous
paragraph)
• Always use a scale to measure actual refrig-
erant R410A charge quantity. Record system
charge when completed.
• The refrigerant must be charged in the liquid
phase for R410A.
• The refrigerant must be charged at the
liquid side of the refrigeration circuit. The
best charging location is the service shut-off
valve at the liquid receiver outlet. When
there is no liquid receiver, the charge must
be done in the liquid line. When a liquid line
solenoid valve (LLSV) is present, it must be
closed (de-energised) and the charge loca-
tion must be before the LLSV.
• If the system is equipped with an electronic
expansion valve (EXV), this valve must be
fully closed (opening degree: 0%).
• Loosely connect the service manifold HP
hose to a gauge fitting on the liquid side as
described above. Connect the LP hose to
a fitting on the suction line as far away as
possible from the compressor.
• The compressor must be off and prevented
from starting inadvertently/automatically.
• If the system is equipped with a liquid line
service shut-off valve, put this valve in an
intermediate position (between front seat
and back seat).
• Start the charging process:
> Using a charging machine the refriger-
ant charge specified can be achieved in
one step
> If using a refrigerant cylinder, it can be
warmed up carefully to avoid generat-
ing over pressure, but increase enough
the tank pressure to allow the complete
transfer.
> If neither EXV nor LLSV is present, take
extra care not filling up the compressor
sump with liquid refrigerant via the
evaporator and suction line.
• “Crack” open the LP service gauge manifold
valve. The pressure in the system LP side
increase slowly until LP pressure equals HP
pressure. The pressure increase at LP side
shall not be faster than 0.25 bar/second. A
brutal pressure increase can cause internal
compressor damage because of an excessive
LP/HP compressor side difference.
• Compressor can be started. Make sure the
compressor is not going to run under vacu-
um. If this situation appears then manually
stop and restart the compressor. When a
EXV is used it can be prepositioned at given
opening degree to avoid running at low
evaporating during EXV self adjustment.
Never by-pass the LP pressure switch.
• Allow the system to operate until the design
operating temperature has been achieved
before making final refrigerant charge
adjustment.
• The additional refrigerant charge must be
done on the LP side by slowly throttling
through the Schrader fitting.
• Continue to monitor the system closely
throughout the entire, initial pull-down
period. Observe all operating system pres-
sures and temperatures and make any other
necessary control adjustments. During this
time, the compressor oil level should be
maintained within the sight glass and suc-
tion superheat measured at the compressor