Bitzer ELH7 Bedienungsanleitung Seite 43

▶ Extract the medium from the line filter and flush it with pure nitrogen.
▶ Remove all oil from the pipes and flush them with pure nitrogen.
▶ Dispose of cloths containing oil in fireproof containers.
▶ Evacuate system components that can be shut off, charge them with pure nitrogen and then shut them off. This
also applies to a dismounted compressor.
▶ Always mark dismounted components with the warning sign "flammable material" W021 from ISO7010.
2.1.6 Used oil from systems with A3 or A2L refrigerants
NOTICE
!
!
Fire hazard!
The used oil contains a relatively large amount of dissolved refrigerant.
Pack used oil safely. Dispose of in an environmentally friendly manner.
Hydrocarbons, for example propane, R290 or propene, R1270 and low-fluorinated flammable refrigerants, for
example R1234yf, dissolve very well in refrigeration compressor oil at room temperature. This also applies to
blends containing these substances.
Used oil from such systems may still contain relatively high percentages of dissolved flammable gases even at
atmospheric pressure. These components gas out.
Observe during storage and transport:
▶ Fill used oil into pressure resistant vessels.
▶ Fill vessels with nitrogen as a protective gas and close them.
▶ Mark them, e. g. with the warning sign "flammable substance" W021 from ISO7010.
3 Operation with frequency inverter
3.1 Refrigerating capacity and system efficiency
Mechanical capacity control
In medium and large HVAC (heating, ventilation and air conditioning) systems like air cooled liquid chillers, a com-
mon method of capacity control are multi-compressor circuits where multiple compressors are switched on and off.
The properly sized liquid loop generally provides a damper for changes in fluid temperature caused by switching in-
dividual compressors on and off. The system controller ‒ along with various fluid and ambient temperature sensors
‒ provides the logic for compressor staging to maintain the desired fluid temperature.
The compressor is operated at a constant speed, the motor speed correlates directly with the mains supply fre-
quency.For 2-pole asynchronous motors, this results in a nominal speed of
-1
• 2900 min at 50 Hz and
-1
• 3500 min at 60 Hz.
For high energy efficiency, high control accuracy of fluid temperature or very low load conditions, frequency invert-
ers can be of advantage for capacity control.
Capacity control with frequency inverter
The average load torque at the compressor shaft mainly depends on operating conditions and refrigerant proper-
ties. Thus, it remains approximately constant over a wide range of speed / frequency. Refrigerating capacity and
power consumption therefore vary approximately proportional to the speed (see graph below), refrigerating capa-
EST-420-6 // PDF Download 43