IOM / @DNOVA_THS-0508
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4.
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 -
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 gau
ge (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).
5. Charging positions [single point]
The best position for charging the air conditioners is the section between the thermostatic valve and the
evaporator; care should be taken to avoid fixing the thermostat bulb until the operation is complete: this is
important to ensure that the valve orifice remains open so as to allow the passage of refrigerant also toward the
condenser/receiver.
If possible, avoid the inflow of refrigerant into the compressor as this may cause excessive dilution of the
lubricant; in any case, first check the compatibility between the crankcase capacity and the required charge
volumes.
Oil T
Pressure
% R.... in oil
T1
T2
T3