Evacuating A Circuit "Contaminated" With Refrigerant; Charging Positions (Single Point) - Lennox Adnova THS Series Installation, Operating And Maintenance Manual

4.3

Evacuating a circuit "contaminated" with refrigerant

The first step is to remove the refrigerant from the circuit. To do this a specific machine is necessary with a drying
compressor in order to recover the refrigerant.
Refrigerants all tend to dissolve in oil (compressor sump). The Fig. 5 illustrates a specific property (Charles' Law) of
gases, which are more soluble in liquids as the pressure increases but less soluble as the temperature increases.
Fig. 5 Charles' law diagram
Pressure
1 ) The release of refrigerant from the cooling circuit tends to cool down the oil and thus actually creates the
opposite effect by keeping more refrigerant dissolved in the oil: for this reason, it is advisable to switch on -if
available- the crankcase heater during the evacuation process.
2 ) If a high % of refrigerant gets in contact with the Pirani gauge (vacuum sensor), it may "mislead" this sensitive
sensor and misinterpret the value 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 heater and to avoid full vacuum
before the circuit has been adequately purged of refrigerant. The refrigerant may in fact dissolve in the oil of the
vacuum pump, reducing its performance for a long time (hours).
4.4 Charging positions (single point
The best position to charge the unit is the section between the thermostatic valve and the evaporator. Take care to avoid
the fixing of the thermostat bulb until the operation is completed. It is important to ensure that the valve orifice remains
open in order to allow the passage of refrigerant also towards the condenser / liquid receiver.
If possible, avoid the charge of refrigerant into the suction line of the compressor as this may cause excessive dilution of
the lubricant. In any case verify first the necessary volume of the crankcase and compare it with the required charge
volumes.
@DNOVA THS_R410A-IOM-1304-E
T oil
% of refrigerant in oil
)
T3
T2
T1
11