Operation With Frequency Inverter; Refrigerating Capacity And System Efficiency - Bitzer EST-420-3 Bedienungsanleitung

Personal protective equipment
When working on systems and their components: Wear protective work shoes, protective clothing and safety
goggles. In addition, wear cold-protective gloves when working on the open refrigeration circuit and on components
that may contain refrigerant.
Fig. 2: Wear personal protective equipment!
Safety references
Safety references are instructions intended to prevent hazards. They must be stringently observed!
NOTICE
!
!
Safety reference to avoid situations which may result in damage to a device or its equipment.
CAUTION
Safety reference to avoid a potentially hazardous situation which may result in minor or moderate injury.
WARNING
Safety reference to avoid a potentially hazardous situation which could result in death or serious injury.
DANGER
Safety reference to avoid an imminently hazardous situation which may result in death or serious injury.
In addition to the safety references listed in this document, it is essential to observe the references and residual
risks in the respective operating instructions!
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.
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