Bitzer 2KTE-7K, Operating Instructions Manual

Page: 25 / 44

KB-130-6 25
• If the system pressure exceeds 20 bar in the me-
dium temperature stage, ensure that the solenoid
valves at the evaporator are shut (de-energised)
• Start the manual operation of the ventilators/water
supply of the gas cooler.
• Continue to charge the intermediate pressure re-
ceiver of the system with liquid CO
2
(the minimum li-
quid level in the container should be reached).
!
!
Notice!
If the pressure in the intermediate pressure re-
ceiver exceeds 30 bar, stop charging refriger-
ant!
• Further proceeding, see chapter Compressor start,
page 25.
5.3 Compressor start
!
!
Notice!
Avoid strong pressure reduction in the crank-
case during the compressor start and during op-
eration!
Oil foam formation and therefore insufficient lub-
rication!
Information
For 2-stage, cascade or booster systems, first
commission the medium temperature stage.
Start the low temperature stage only after con-
stant operating conditions are achieved. For
booster systems with flash gas bypass and
without internal heat exchanger for flash gas
evaporation, it is recommended to adapt the
commissioning process. An early commission-
ing of the low temperature stage can minimize
the influence of liquid portion in the flash gas on
the compressors of the medium temperature
stage.
◦ Before starting the first compressor / evaporator:
Choose the right evaporation capacity according to
the compressor performance.
• Open the discharge shut-off valve and the suction
shut-off valve of the CO
2
compressor. In large sys-
tems with high-capacity evaporators and long pipes,
proceed very carefully and keep the suction shut-off
valve in throttling position.
• Switch on the compressors (for parallel circuits, first
switch on only one compressor). In large systems,
maintain the suction shut-off valve in throttling posi-
tion. As soon as the suction pressure decreases,
slowly start opening until it is completely open. At the
same time, switch on the solenoid valves of the
evaporator, if necessary, in accordance with the
compressor capacity.
• If there is not enough refrigerant: Adjust refrigerant
quantity, if necessary.
• Fill the suction side with gaseous, or the intermedi-
ate pressure receiver with liquid CO
2
. Avoid strong
pressure increase.
• If the operating limits are exceeded or if abnormal
conditions occur (e.g. wet operation), switch off im-
mediately the compressors.
• Only switch on again when the pressure situations
are stabilised or after elimination of the fault.
• Avoid high switching frequencies!
• Depending on the system type and control system,
connect further compressors and evaporators if ne-
cessary. Adjust the refrigerant charge.
The commissioning of the low temperature stage is
done the same way.
Particular measures for cascade systems:
• Before starting a compressor, activate the solenoid
valve or the electronic expansion valve to the cas-
cade heat exchanger in the medium temperature
system. Refrigerant injection on evaporator side of
the heat exchanger results in CO
2
condensation.
5.3.1 Checking the operating data
After successful commissioning and charging of refri-
gerant, check the operating data and prepare a data
protocol:
• Evaporation temperatures and high pressure – see
application limits KP-130 or KP-132.
• Suction gas temperature, discharge gas temperature
and oil temperature, see chapter Operating temper-
atures and lubrication conditions, page 26.
• Switching frequency:
– max. 6 starts per hour
– min. time for a start / stop cycle = 10 min
• Current values of all phases.
• Voltage.