66 RTAA-SVX01A-EN
Operating Principles
This section describes the mechanical operating principles of Series R
air-cooled chillers equipped with microcomputer-based control systems.
The 70 - 125-ton Model RTAA units are dual-compressor, helical-rotary type
air-cooled liquid chillers. The basic components of an RTAA unit are:
• Clear Language Display.
• Unit Control Modules (UCM).
• Unit-mounted panel.
• Helical-rotary compressor.
• Direct Expansion evaporator.
• Air-cooled condenser.
• Oil supply system (hydraulic and lubrication).
• Interconnecting piping.
Refrigeration (Cooling) Cycle
Cycle Description
Figure 32 represents the refrigeration system and control components.
Vaporized refrigerant leaves the evaporator and is drawn into the compressor.
Here it is compressed and leaves the compressor as a mixture of hot gas and
oil (which was injected during the compression cycle).
The mixture enters the oil separator at the in/out cap. The separated oil flows
to the bottom of the separator, while the refrigerant gas flows out the top and
passes on to the tubes in the condensing coils. Here circulating air removes
heat from the refrigerant and condenses it.
The condensed refrigerant passes through the electronic expansion valve and
into the tubes of the evaporator. As the refrigerant vaporizes, it cools the
system water that surrounds the tubes in the evaporator.
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