OPERATING INSTRUCTIONS
CO
2
/NH
3
CASCADE UNIT
250 - 1000 KW
_551511_om_kas_gbr_1_.doc 43
To this end there is a level measurement probe (item
6900) on the separator, whose signal is detected by
the GSC control and indicates the charge level.
Place the refrigerant cylinder on weighing scales
during the charging process to check the charged
volume.
Avoid overcharging the refrigerant circuit to prevent
wet steam from being sucked into the compressor.
4.4.4 Draining the refrigerant
After the pressure has equalized between the
cascade and refrigerant cylinder, a pressure
difference for further charging can be generated by:
4.4.4.1 General notes on draining refrigerant
This action is required:
— if the system is overfilled
— the compressor of the cascade (for initial
startup) or
— if the refrigerant or oil circuit is dismantled and
repaired
— a connected auxiliary compressor.
— for maintenance work on the oil circuit
Once the circuit has been charged, the cylinder and
refrigerant charging valves should be closed tight.
The refrigerant charging line and the refrigerant
cylinder are to be removed.
— if foreign gases are detected in the system
Whenever work is carried out on the parts of the
refrigerating system carrying refrigerant or oil,
extreme caution is required as leaking refrigerant
can cause hazards.
The system is in normal operation.
4.4.3 Charging characteristics
For health and safety reasons, safety goggles and
protective gloves must be worn.
Comply with the charge quantities of the respective
refrigerant circuits given on the manufacturer's name
plate or in the technical documentation of the
CO
When work is carried out on the cascade, the
refrigerant and oil must be moved to storage
locations or disposed in accordance with the
regulations and with the least possible loss.
/NH cascade.
2 3
The cascade's performance is reduced when it is
under or over-charged.
If any liquid refrigerant is still left in the section to be
opened, continue drawing it off until it evaporates.
The cascade charge can only be correctly assessed
during operation (steady state, full load).
Caution!
circuit
NH
3
Watch out for possible risk due to
residual refrigerant!
If the cascade is correctly filled, a liquid level can be
seen in the upper sight glass of the external
circulation line (not separator) of the cascade heat
exchanger during operation.
4.4.4.2 Charging refrigerant
Undercharging characteristics:
The liquid refrigerant can be removed from the
system and transferred into refrigerant cylinders or
suctioned off as refrigerant vapour using an
extraction device.
— During operation the liquid level can only be
seen in the lower sight glass or not at all
— Excessive intake superheating
The cylinders into which the refrigerant is transferred
must be evacuated and cooled beforehand.
— Evaporation temperature too low
— No refrigeration
A sufficient number of cleaned, dry and subcooled
cylinders must be made available ready for use
before starting to empty the refrigerant. The
refrigerant cylinder must be placed on the weighing
scales.
— Cascade is switched off because of negative
pressure/partial vacuum
— Unallowably high compressed gas temperature
Overcharging characteristics:
The charging hose is securely screwed to the service
valve of the respective refrigerant cycle at one end
and to the valve of the refrigerant cylinder or
extraction device at the other end. Then the service
valve and then the flange valve are opened slowly.
— level can be seen in the liquid separator's sight
glass.
circuit
CO
2
The CO
2
circuit's charge is detected by the level of
the liquid CO
The refrigerant cylinder charge is measured using
weighing scales whereby it must be taken into
account that the cylinder may only be filled up to
in the liquid separator (item 6000).
2
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