Installation and Maintenance Manual

RTWD/RTUD Operating Principles
126 RLC-SVX09H-EN
Refrigeration (Cooling) Cycle
Overview
The refrigeration cycle of the Series R chiller is
conceptually similar to that of otherTrane chiller products.
It makes use of a shell-and-tube evaporator design with
refrigerant evaporating on the shell side and water flowing
inside tubes having enhanced surfaces.
The compressor is a twin-rotor helical rotary type. It uses
a suction gas-cooled motor that operates at lower motor
temperatures under continuous full and part load
operating conditions. An oil management system
provides an almost oil-free refrigerant to the shells to
maximize heat transfer performance, while providing
lubrication and rotor sealing to the compressor.The
lubrication system ensures long compressor life and
contributes to quiet operation.
For RTWD units, condensing is accomplished in a shell-
and-tube heat exchanger where refrigerant is condensed
on the shell side and water flows internally in the tubes.
For RTUD units, condensing is accomplished in a remote
air-cooled condenser unit.The refrigerant flows through
the tubes in the condenser. Air flows over the coils in the
condenser, removing the heat and condensing the
refrigerant.
Refrigerant is metered through the flow system using an
electronic expansion valve, that maximizes chiller
efficiency at part load.
A unit-mounted starter and control panel is provided on
every chiller. Microprocessor-based unit control modules
(Tracer CH530) provide for accurate chilled water control
as well as monitoring, protection and adaptive limit
functions.The “adaptive” nature of the controls
intelligently prevents the chiller from operating outside of
its limits, or compensates for unusual operating
conditions, while keeping the chiller running rather than
simply tripping due to a safety concern. When problems
do occur, diagnostic messages assist the operator in
troubleshooting.
Cycle Description
The refrigeration cycle for the RTWD/RTUD chiller can be
described using the pressure-enthalpy diagram shown in
Figure 48, p. 127. Key State Points are indicated on the
figure and are referenced in the discussion following. A
schematic of the system showing the refrigerant flow loop
as well as the lubricant flow loop is shown in
Figure 47. RTWD/RTUD components (back view)
Circuit 2 Circuit 1
Discharge Service Valve
Compressor Junction Box
Refrigerant Filter
Liquid Level Sensor
Oil Cooler (optional on RTWD)
Gas Pump
(behind frame)
Base rail for forklifting
(optional)
Condenser
(RTWD only)