Refrigerant Cycle - Trane CGAM Installation & Operation Manual

CGAM Operating Principles

Refrigerant Cycle

The refrigeration cycle of the Model CGAM chiller is conceptually similar to other Trane air-cooled
chiller products. The CGAM chiller uses a brazed plate evaporator and an air-cooled condenser. The
compressors use suction gas cooled motors and an oil management system to provide almost oil-
free refrigerant to the condenser and evaporator for maximum heat transfer while lubricating and
sealing compressor bearings. The lubrication system helps to assure long compressor life and
contributes to quiet operation.
Refrigerant condensers in the air-cooled heat exchanger which is available in three
configurations—slant, V and W—based on the CGAM nominal tonnage cooling capacity. Liquid
refrigerant is metered into the brazed plate evaporator using an electronic expansion valve to
maximize chiller efficiency at full and part load operation.
The CGAM chiller is equipped with a unit-mounted starter and control panel. Microprocessor-based
unit control modules (Trane Tracer™CH530) provide accurate chilled water control and provide
monitoring, protection and adaptive limit functions. The adaptive nature of the controls
intelligently prevent the chiller from operating outside of its limits, or compensates for unusual
operating conditions while keeping the chiller running rather than simply shutting off the chiller.
If problems do occur, the CH530 controls provide diagnostic messages to help the operator in
troubleshooting.
Refrigerant Cycle Description
The CGAM refrigeration cycle is described using the pressure-enthalpy chart shown in
Key State Points 1 through 5 are indicated on the chart. A schematic showing refrigerant
components throughout the system is shown in
Refrigerant evaporation occurs in the brazed plate evaporator. Metered refrigerant vaporizes as it
cools the chilled water or liquid flowing through the evaporator passages. The refrigerant vapor
leaves the evaporator as superheated gas. State Point 1.
Refrigerant vapor generated in the evaporator flows to the compressor suction manifold where it
enters and flows across the compressor motor windings to provide cooling. The vapor is then
compressed in the compressor scroll chambers and discharged. Oil from the compressor sump
lubricates the bearings and seals the small clearances between the compressor scrolls. Refrigerant
vapor is discharged to the air-cooled condenser at State Point 2.
After the refrigerant vapor condenses into liquid (State Points 3 and 4) it is returned to the
evaporator (State Point 5) where the refrigerant again flashes into vapor and the refrigeration cycle
repeats.
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Figure 77.
Figure 76.
CG-SVX17D-EN