Lennox INNOV DM R Series Application Manual page 90

steps of evacuation need to be repeated as described before. This operation facilitates the removal of remaining
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. 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. 10 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.
Pressure
Fig. 10 Charles' law diagram
If the oil in the sump is held at a constant pressure, an increase in temperature will significantly reduce the
amount of refrigerant dissolved in it, thus ensuring that the lubricating function desired is maintained. The
problem of inadequate lubrication occurs if the crankcase is not duly heated, above all after seasonal
interruptions when, due to the suction effect of the compressor, there is an abrupt drop in pressure inside the
sump, which results in considerable evaporation of the refrigerant previously dissolved in the oil. If heating
elements were
problems:
1 ) The
cool down the oil and thus actually
keeping more refrigerant dissolved
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.
INNOV@ CENT -AGU-0912-E
T oil
T3
T2
not installed, this phenomenon would cause two
T1
release of refrigerant from the cooling circuit tends to
% di Refrigerant in oil
)
creates the opposite effect by
in the oil: for this reason, it is
. 14 .