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All compressors get a factory holding charge of dry air (about 0.2 to 0.7 bar, relative pressure. The
presence of a holding charge serves as a proof of quality against moisture penetration.
When removing plugs from the compressor, the plugs may pop out due to pressure and oil can spurt.
Any later modification to compressor connections can have an impact on the compressor tightness.
Always leak test the compressor after opening or modifying the connections.
Never add refrigerant to the test gas (as leak indicator).
5.3 System evacuation
Before the installation is put into commission, it has to be evacuated with a vacuum pump. The
vacuum pump and all tools have to be approved for an A2L or A3 refrigerant/air mixture. The
installation should be evacuated down to an absolute pressure of 3 mbar. Proper evacuation reduces
residual moisture to 50 ppm.
The installation of adequately sized access valves at the furthest point
from the compressor on the suction and liquid lines is advisable. The pressure must be measured
using a vacuum pressure gauge on the access valves and not on the vacuum pump; this serves to
avoid incorrect measurements resulting from the pressure gradient along the connecting lines to the
pump.
Evacuating the system only on the suction side of a scroll compressor can occasionally result in a
temporary no-start condition for the compressor. The reason for this is that the floating seal could
axially seal with the scroll set, with the higher pressure on the floating seal. Consequently, until the
pressures equalise, the floating seal and scroll set can be held tightly together.
The highest demands are placed on the leak-proof design of the installation and on the leak testing
methods
– refer to, eg, EN 378.
When working on systems already filled with refrigerant, it may be necessary to carry out several
evacuation processes. Refrigerant may have dissolved in the refrigerant oil and will only gradually
condense out.
5.4 Preliminary checks
– Pre-starting
WARNING
Air/A2L or A3 refrigerant mixture in a potentially flammable or explosive
atmosphere! Fire and explosion hazard!
Whenever starting up a system
charged with A2L or A3 refrigerant, eg, after filling, repair, or maintenance,
make sure not to start and operate accidentally in a flammable or explosive
atmosphere.
Prepare all details of the system before the installation. If possible, obtain drawings, wiring diagrams,
etc. It is ideal to use a check-list but always check the following:
▪
no explosive atmosphere or flammable gas in the ambient;
▪
suitable ventilation according to room volume and refrigerant charge;
▪
visual check of the electrics, wiring, fuses etc;
▪
visual check of the plant for leaks, loose fittings such as TXV bulbs etc;
▪
compressor oil level;
▪
calibration of HP & LP switches and any pressure-actuated valves;
▪
check setting and operation of all safety features and protection devices;
▪
all valves in the correct running position;
▪
pressure and compound gauges fitted;
▪
correctly charged with refrigerant;
▪
compressor electrical isolator location & position.
