Trane Flex II Series Installation Operation & Maintenance page 31

12.1.2 Refrigerant replacement procedure with unit running (refrigerant charge in the vapour phase)
Caution: charge vapour only. Do not charge liquid because it may damage the compressor.
Connect the refrigerant cylinder to the service valve without tightening the coupling. Drain the connection piping and
tighten the coupling. Charge each circuit until the indicator indicates liquid without bubbles. Now the unit has the
required charge. Make sure not to overcharge the circuit. Charging more than necessary leads to a higher delivery
pressure, greater power consumption and possible damage to the compressor.
The symptoms of a low refrigerant charge are:
Low evaporation pressure.
High superheat the intake and exhaust (outside the above limits).
Low value of subcooling.
In this case, add refrigerant R410A. The system has a charging port between the expansion valve and the evaporator.
Charge refrigerant until conditions return to work normal. Remember to replace the cap closing the valve at the end.
IMPORTANT!
If the unit has not been provided with integrated pump on board, do not turn off the external pump before 3 minutes
have elapsed after turning off the last compressor. The early shutdown of the pump causes a water flow alarm failure.
Refrigerant charge in the vapour phase
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