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6| Commissioning
6.5
Refrigerant charge
Make sure that the suction and pressure line shut-off valves are open.
With the compressor switched off, add the liquid refrigerant directly to the condenser or receiver,
breaking the vacuum.
If the refrigerant needs topping up after starting the compressor, it can be topped up in vapor form
on the suction side, or, taking suitable precautions, also in liquid form at the inlet to the evapora-
tor.
6.6
Start-up
Check that the safety and protection devices (pressure switch, motor protection, electrical
contact protection measures, etc.) are all functioning properly.
Switch on the compressor and allow to run for a minimum of 10 min.
Check the oil level by: The oil must be visible in the sight glass.
6.7
Avoiding slugging
To prevent slugging:
The complete refrigeration system must be properly designed.
All components must be compatibly rated with each other with regard to output
(particularly the evaporator and expansion valves).
Suction gas superheat at the compressor input should be min. 7 - 10 K. (check the setting
of the expansion valve).
The system must reach a state of equilibrium.
Particularly in critical systems (e.g. several evaporator points), measures are recommended such
as replacement of liquid traps, solenoid valve in the liquid line, etc.
There should be no movement of coolant whatsoever while the compressor is at a
standstill.
Wear personal protective clothing such as goggles and protective
gloves!
Avoid overfilling the system with refrigerant!
To avoid shifts in concentration, zeotropic refrigerant blends must
always only be filled into the refrigerating plant in liquid form.
Do not pour liquid coolant through the suction line valve on
the compressor.
It is not permissible to mix additives with the oil and
refrigerant.
Ensure that both shut-off valves are open before starting the
compressor!
If larger quantities of oil have to be topped up, there is a risk of
oil hammer effects.
If this is the case check the oil return!
Slugging can damage the compressor and cause refrigerant to
leak.
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