Trane CG-PRC007-EN - Manual (Page 49)

49 CG-PRC007-EN
Mechanical
Specifications (20–60 Ton)
GENERAL
All chillers are factory run-tested to
confirm proper operation. Units are
checked on a computer-based test stand
at typical ambient and water conditions
and control operation is monitored.
Units ship with a full operating charge of
refrigerant and oil.
Units are constructed of 14-gauge
welded galvanized steel frame with 14
and 16-gauge galvanized steel panels
and access doors. Unit surface is
phosphatized and finished with an air-
dry paint. This air-dry paint finish is
durable enough to withstand a 1000-
consecutive-hour salt spray application
in accordance with standard ASTM B117.
Evaporator
Braze plate construction designed to
withstand a waterside working pressure
of 300 psig and a refrigerant side
working pressure of 225 psig. It has one
water pass. Etched foil heaters protect
the evaporator to an ambient of -20°F.
Flow Switch
This factory supplied item indicates the
loss of evaporator flow and ships with
the unit for field installation.
Strainer (with installation hardware)
The strainer is required to prevent
collection of particles within the
evaporator.
Condenser
Air-cooled condenser coils have
configurated aluminum fins
mechanically bonded to seamless
copper tubing and integral subcooling
circuits. Condensers are factory leak-
tested with air underwater at 425 psig air
pressure.
Direct-drive vertical discharge condenser
fans are statically and dynamically
balanced. Three-phase condenser fan
motors with permanently lubricated ball
bearings and three-phase thermal
overload protection. Optional low
ambient units start and operate to 0°F
with electronic damper assemblies for
head pressure control.
Decorative grilles provide protection
from exterior damage to coil surface and
other interior unit components. Grilles
are factory mounted, louvered,
galvanized steel mesh panels finished
with an air-dry paint. Grilles will cover all
open ends of units.
Compressors
Trane 3-D Scroll compressors have
simple mechanical design with only
three major moving parts. Scroll type
compression provides inherently low
vibration. The 3-D Scroll provides a
completely enclosed compression
chamber which leads to increased
efficiency. Exhaustive testing on the 3-D
Scroll, including start up with the shell
full of liquid, has proven that slugging
does not fail involutes. Direct-drive, 3600
rpm, suction gas-cooled hermetic motor.
Trane 3-D Scroll compressor includes
centrifugal oil pump, oil level sight glass
and oil charging valve. Each compressor
shall have crankcase heaters installed,
properly sized to minimize the amount of
liquid refrigerant present in the oil sump
during off cycles.
Refrigerant Circuits and Capacity
Modulation
Twenty to 30-ton sizes have a single
refrigerant circuit. Forty to 60-ton sizes
have dual refrigerant circuits. Each
refrigerant circuit has two Trane 3-D
Scroll compressors, piped in parallel,
with a passive oil management system.
Passive oil management system
maintains proper oil levels within
compressors and has no moving parts.
Each refrigerant circuit includes a liquid
line solenoid valve, filter drier, liquid line
sight glass with moisture indicator,
thermostatic expansion valve, and
service valves (liquid and discharge).
Capacity modulation is achieved by
turning compressors on and off. Twenty
to 30-ton sizes have two capacity stages.
Forty, 50 and 60-ton sizes have four
capacity stages. The standard leaving
chilled water temperature range is 40°F
to 50°F. Options are available for leaving
chilled solution temperature ranges from
20° to 29°F, 30° to 39°F, and 51° to 65°F.
Unit Controls
Compressor contactors and unit controls
are in a weather tight enclosure with
knockouts for jobsite installed wiring. The
unit controller shall be suitable to control
leaving chilled solution temperature for
comfort or process applications,
automatic compressor sequencing,
condenser fan sequencing, load limiting
and anti-recycle functions. Failure
protections include loss of chilled
solution flow, chiller freeze protection,
chilled solution flow interlock, head
pressure control, pump down control,
low ambient start, hot start control, and
low ambient lockout. Leaving and
entering solution temperature sensor is
factory installed. Controls include
auto/stop switch, a leaving water
temperature set point adjustment, a
Delta T adjustment viewable through the
unit Human Interface digital display.
Unit Controller
DDC microprocessor controls shall be
provided to control all unit functions. The
control system shall be suitable to
control comfort and process
applications. The controls shall be
factory-installed and mounted in the
main control panel. All factory-installed
controls shall be fully commissioned
(run tested) at the factory. The unit shall
have a Human Interface Panel with a 16
key keypad, a 2 line X 40 character clear
English display as standard to provide
the operator with full adjustment and
display of control data functions. The unit
controls shall be used as a stand-alone
controller, or as part of a building
management system involving multiple
units.
1
The unit shall be equipped with a
complete microprocessor control
system. This system shall consist of
temperature and pressure (thermistor
and transducer) sensors, printed circuit
boards (modules), and a unit mounted
Human Interface Panel. Modules
(boards) shall be individually replaceable
for ease of service. All microprocessors,
boards and sensors shall be factory
mounted, wired and tested.
The microprocessor boards shall be
stand-alone DDC controls not dependent
on communications with an on-site PC
or a Building Management Network. The
microprocessors shall be equipped with
onboard diagnostics, indicating that all