KB-130-7
13
• 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 with refri-
gerant!
Parametrise the system controller so that the
flash gas bypass valve of the first compressor
opens!
• Further proceeding, see chapter Compressor start,
6.3
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 adjusting 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.
• Check the settings of the refrigerated display cabinet
controllers (especially protective functions like the
maximum allowable pressure, etc.).
• Open the discharge gas shut-off valve and the suc-
tion gas shut-off valve of the CO
2
compressor. In
large systems with high-capacity evaporators and
long pipes, proceed very carefully and keep the suc-
tion gas shut-off valve in throttling position. For small
and medium-sized systems: Switch the compressor
to ready-to-operate in the Automatic mode. Switch
the evaporator on and observe the suction gas pres-
sure; if needed, decommission the evaporator again
and select a lower evaporator capacity for the start
once the suction gas pressure has been reduced.
• Switch the compressor on (for parallel circuits,
switch on only one compressor first). In large sys-
tems, maintain the suction gas shut-off valve in throt-
tling position. As soon as the suction pressure de-
creases, 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 the refriger-
ant quantity as needed.
• Charge the suction side with gaseous CO
2
or the in-
termediate pressure receiver with liquid CO
2
. Avoid a
strong increase in pressure.
• If the operating limits are exceeded or if abnormal
conditions occur (e.g. wet operation), switch the
compressors off immediately.
• Only switch on again when the pressure levels are
stable or after elimination of a possible fault.
• Avoid high cycling rates!
• Depending on the system type and control system,
connect further compressors and evaporators if ne-
cessary. Adjust the refrigerant charge.
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.
For parallel operation:
• Commissioning for parallel operation is performed as
with medium temperature applications. However,
without the parallel compressors, the maximum per-
formance of the system is substantially reduced. The
maximum performance of the system cannot be re-
called until the parallel compression stage has been
completely commissioned.
6.3.1
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, KP-132 and KP-133.
• Suction gas temperature, discharge gas temperature
and oil temperature, see chapter Operating temper-
atures and lubrication conditions, page 14.
