CC7.8.9/0519/E
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5
Charging the CO
2
refrigeration unit
CAUTION
High pressures! Risk of system damage!
Only use pressure gauges that are suitable
for the required pressure positions. Check the connection hoses for suitability for CO
2
pressure levels.
After leakage tests and evacuation have been performed, the system can be filled with R744 refrigerant. In
order to avoid the formation of dry ice, the system must be filled with gas on both sides first. Gaseous filling to
10 bar is common practice.
NOTE: Only pressure gauges and connection hoses suitable for high-pressure refrigerants can be
used.
Figure 6: Pressure gauges and connection hoses
After filling to approximately 10 bar on both sides, liquid CO
2
can be filled into the liquid receiver. After
pressures in the refrigeration system and the CO
2
tank have equalised, the missing refrigerant must be refilled
in gaseous form via the suction side.
For this purpose, the isolating switches for compressors (
F1
) and fans (
F3
) must be switched on and the
release for the frequency inverter (
SB1
) must be activated.
Figure 7: Enabling compressors, fans & frequency inverter
The refrigeration unit starts automatically. First the gas cooler fans start up, then the compressor switches on
and starts controlling according to suction pressure. The filling process via the suction side can be completed.
The system should be charged according to the liquid level in the bottom sight glass on the liquid receiver. As
soon as the bottom sight glass is completely charged with liquid CO
2
, a sufficient refrigerant charge is available.
The influence of the ambient temperature is negligible, as the pressure in the liquid receiver is regulated and
therefore the temperature in the receiver is constant. At low pressure in the refrigerant bottle, the evaporation
pressure "
SETC1
" can be set low to enable filling from the suction side.
During normal operation, the upper sight glass should not contain liquid refrigerant. Refrigerant in the upper
sight glass would be an indication of system overfilling. During pumpdown however, refrigerant may be present
in the upper sight glass.
