Trane Flex II Series Installation Operation & Maintenance page 30

12.1 REFRIGERANT CHARGE
12.1.1 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 subcooling of 4 - 8°C. Values of
overheating which are too high may be caused by a lack of refrigerant, whereas high subcooling 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 condenser and read the balance pressure to the condenser on the high -pressure
manometer and the corresponding saturation temperature. The subcooling 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 circuit diagram with connection to vacuum
pump
Refrigerant charge in the liquid phase
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