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Operating Principles
Refrigerant Circuit
Each unit has two refrigerant circuits, with one or two
rotary screw compressors per circuit. Each refrigerant
circuit includes compressor suction and discharge service
valves, liquid line shut off valve, removable core liquid line
filter, liquid line sight glass, charging port, pressure relief
valves on both high and low side of system, and electronic
expansion valve. Fully modulating compressor and
electronic expansion valve provide variable capacity
modulation over the entire operating range.
Refrigerant Cycle
Typical refrigerant cycle is represented on the pressure
enthalpy diagram shown in the figure below. Key state
points are indicated on the figure. The cycle for the full
load design point is represented in the plot.
Figure 36. Pressure-enthalphy diagram
600
500
200
3b
100
4
50
30
0
20
40
The chiller uses a shell and tube evaporator design with
refrigerant evaporating on the shell side and water flowing
inside tubes having enhanced surfaces (states 4 to 1). The
suction lines are designed to minimize pressure drop
(states 1 to 1b) the compressor is a twin-rotor helical rotary
compressor designed similarly to the compressors
offered in other Trane screw compressor based chiller
(states 1b to 2). The discharge lines include a highly
efficient oil separation system that removes 99.8% of the
oil from the refrigerant stream going to the heat
exchangers (states 2 to 2b). De-superheating, condensing
and sub-cooling are accomplished in a microchannel air-
air-cooled heat exchanger where refrigerant is condensed
inside the microchannel (states 2b to 3b). Refrigerant flow
through the system is balanced by an electronic expansion
valve (states 3b to 4).
RTAF-SVX001K-EN
R-134a
3
1
1b
60
80
100
120
h (btu/lb)
Refrigerant and Oil
Use only R-134a or R-513A as shown on unit nameplate,
and selected in unit model number digit 16.
Digit 16 =1 or 3: R-513A
Digit 16 = 2 or 4: R-134a
The Sintesis™ chiller uses environmentally friendly
refrigerants. Trane believes that responsible refrigerant
practices are important to the environment, our
customers, and the air conditioning industry. All
technicians who handle refrigerants must be certified. The
Federal Clean Air Act (Section 608) sets forth the
requirements for handling, reclaiming, recovering and
recycling of certain refrigerants and the equipment that is
used in these service procedures. In addition, some states
or municipalities may have additional requirements that
must also be adhered to for responsible management of
refrigerants. Know the applicable laws and follow them.
R-134a and R-513A are medium pressure refrigerants.
They may not be used in any condition that would cause
the chiller to operate in a vacuum without a purge system.
Sintesis is not equipped with a purge system. Therefore,
the chiller may not be operated in a condition that would
2
result in a saturated refrigerant condition in the chiller of
2b
-15°F (-26°C) or lower.
Use only the specific POE oil as designated on the unit
nameplate.
Compressor and Lube Oil System
The rotary screw compressor is semi-hermetic, direct
drive, with rolling element bearings and oil heater. The
140
motor is a suction gas cooled, hermetically sealed, two-
pole squirrel cage induction motor.
An adaptive frequency drive provides capacity control of
the lead compressor on each circuit. For maximum
efficiency, larger tonnage units utilize both fixed speed
and variable speed compressors staged in the same
circuit. Proven Trane controls manage the staging and
loading of the fixed nad variable speed compressors for
maximum unit efficiency and stability.
Oil separator is provided separate from the compressor.
Oil filtration is provided internal to the compressor. Check
valves in the compressor discharge and lube oil system
are also provided.
Condenser and Fans
See
Figure 3, p. 10
The air-cooled microchannel condenser coils use all
aluminum brazed fin construction. The condenser coil has
an integral subcooling circuit. The maximum allowable
working pressure of the condenser is 350 psig.
for condenser fan designator locations.
53
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