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4.2
Vacuum and charging machine
Vacuum cycle
In general it is preferable to apply a "long" rather than "hard" vacuum: reaching low pressures too abruptly
may in fact cause any trapped humidity to evaporate instantaneously, thereby freezing part of it.
Fig. 4
Vacuum cycle diagram
The Fig. 4 represents a vacuum cycle and an optimal subsequent pressure rise for the refrigeration devices
we manufacture. As a rule, if there is suspicion of an extensive presence of humidity throughout the circuit
or system as a whole, the vacuum must be "broken" with anhydrous nitrogen and then the steps must be
repeated as described; this operation facilitates the removal of trapped and/or frozen humidity during the
evacuation process
4.3
Evacuating a circuit "contaminated" with refrigerant
The first step is to remove the refrigerant from the circuit using a specific machine with a dry compressor
for recovering the refrigerant. Refrigerants all tend to dissolve in oil (compressor sump) in percentages that
are directly proportional to increases in pressure and decreases in the T of the oil itself --- Charles' Law ---
(see Fig. 5).
Fig. 5
Charles' law diagram
The release of refrigerant tends to cool the oil and thus actually serves to oppose the release itself: for this reason, it is
advisable to switch on the crankcase heating elements, if available, during the evacuation process. If a high % of
refrigerant gets into contact with the Pirani gauge (vacuum sensor), it may "drug" the sensitive element of the latter,
rendering it inefficient for a certain period of time. For this reason, if no machine for recovering refrigerant is available, it
is nonetheless advisable to switch on the crankcase heating elements and avoid applying a vacuum until the circuit has
been adequately purged of refrigerant: the refrigerant may in fact solubilize in the oil of the vacuum pump, undermining
its performance for a long time (hours).
@DNOVA THN_R410A-IOM-1506-E
.
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