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13.1
REFRIGERANT CHARGE
13.1.1 Refrigerant replacement procedure with unit stopped and in vacuum (refrigerant charge in
the liquid phase)
Open the shut off valve as far as possible so that it closes the service coupling. Connect the refrigerant cylinder
to the service coupling without tightening the coupling. Half close the liquid shut off valve. If the circuit has been
dehydrated and is in vacuum, charge the liquid by turning the cylinder upside down. Weigh and charge the
appropriate quantity. Open the valve completely. Start up the unit and leave it running at full charge for some
minutes. Check that the indicator is clear with no bubbles. Make sure that the transparency condition without
bubbles is due to the liquid and not to the vapour. Correct functioning of the unit allows for overheating of 4 - 7°
C and sub-cooling of 4 - 8°C. Values of overheating which are too high may be caused by a lack of refrigerant,
whereas high sub-cooling values may mean an excess of charge. After intervention on the charge, it is
appropriate to check that the unit runs within the declared values: with unit steadily running on a full charge,
measure the temperature of the suction line downstream of the thermostatic valve bulb; read the balance
pressure to the evaporator on the low pressure manometer and the corresponding saturation temperature.
Overheating is equal to the difference between the temperatures measured in this way. Then measure the
temperature of the liquid line coming out of the remote condenser and read the balance pressure to the remote
condenser on the high -pressure manometer and the corresponding saturation temperature. The sub-cooling is
the difference between these temperatures.
Danger
While refrigerant is being added do not exclude any control system and let the water circulate in the
evaporator to avoid the formation of ice
.
Refrigerant charge in the liquid phase
Refrigerant circuit diagram connection to vacuum pump
High pressure
port
Low pressure
port
High pressure
gauge
Vacuum meter
Vacuum pump
Oil trap
Low
pressure
gauge
Liquid sight glass
HP port
LP port
HP gauge
Scale
LP gauge
Figure 20
Figure 21
Summary of Contents for CCUF
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