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Mechanical Specifications |
General
The units shall be dedicated downflow or horizontal
airflow. The operating range shall be between 115 F and 0 F in cooling as standard from
the factory for all units. Cooling performance shall be rated in accordance with ARI
testing procedures. All units shall be factory assembled, internally wired, fully charged
with HCFC-22 and 100% run tested to check cooling operation, fan and blower rotation and
control sequence before leaving the factory. Wiring internal to the unit shall be
numbered for simplified identification. Units shall be UL listed and labeled, classified
in accordance to UL 1995/CAN/CSA No. 236-M90 for Central Cooling Air Conditioners.
Canadian units shall be CSA Certified.
Casing
Unit casing shall be constructed of zinc coated, heavy
gauge, galvanized steel. All components shall be mounted in a weather resistant steel
cabinet with a painted exterior. Where top cover seams exist, they shall be double hemmed
and gasket sealed to prevent water leakage. Cabinet construction shall allow for all
maintenance on one side of the unit. Service panels shall have handles and shall be
removable while providing a water and air tight seal. Control box access shall be
hinged. The indoor air section shall be completely insulated with fire resistant,
permanent, odorless glass fiber material. The base of the unit shall have provisions for
crane lifting.
Filters
Two inch, throwaway filters shall be standard on all size
units. Two inch "high efficiency", and four inch "high
efficiency" filters shall be optional.
Compressors
Trane 3-D® Scroll compressors have a simple mechanical design with only three
major moving parts. Scroll type compression provides inherently low vibration. 3-D
compliance provides a completely enclosed compression chamber which leads to
increased efficiency. Exhaustive testing on the 3D 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 sightglass and oil charging valve. Control of
compressor shall allow lead/lag of multiple compressors/circuits for even run time to
increase life of compressors.
Refrigerant Circuits
Each refrigerant circuit shall have independent
thermostatic expansion devices, service pressure ports and refrigerant
line filter driers factory-installed as standard. An area shall be provided for
replacement suction line driers.
Evaporator and Condenser Coils
Condenser coils shall have 3 /8 " copper tubes
mechanically bonded to lanced aluminum plate fins. Evaporator coils shall be 1 /2 "
internally finned copper tubes mechanically bonded to high performance aluminum plate
fins. All coils shall be leak tested at the factory to ensure pressure integrity. All
coils shall be leak tested to 200 psig and pressure tested to 450 psig. All dual circuit
evaporator coils shall be of intermingled configuration.
Outdoor Fans
The outdoor fan shall be direct-drive, statically and
dynamically balanced, draw through in the vertical discharge position. The fan motor(s)
shall be permanently lubricated and have built-in thermal overload protection.
Indoor Fan
Units shall have belt driven, FC, centrifugal fans with
fixed motor sheaves. All motors shall be circuit breaker protected. All indoor fan motors
meet the U.S. Energy Policy Act of 1992 (EPACT).
Electric Heaters
Electric heat shall be available for factory installation
within basic unit. Electric heater elements shall be constructed of heavy-duty nickel
chromium elements internally delta connected for 240 volt, wye connected for 480 and
600 volt. Staging shall be achieved through the unitary control processor (UCP). Each
heater package shall have automatically reset high limit control operating through heating
element contactors. All heaters shall be individually fused from factory, where required,
and meet all NEC and CEC requirements. Power assemblies shall provide single-point
connection. Electric heat shall be UL listed or CSA certified.
Gas Heating Section
The heating section shall have a drum and tube heat
exchanger(s) design using corrosion resistant steel components. A forced combustion blower
shall supply premixed fuel to a single burner ignited by a pilotless hot surface ignition
system. In order to provide reliable operation, a negative pressure gas valve shall be
used that requires blower operation to initiate gas flow. On an initial call for heat, the
combustion blower shall purge the heat exchanger(s) 45 seconds before ignition. After
three unsuccessful ignition attempts, the entire heating system shall be locked out until
manually reset at the thermostat. Units shall be suitable for use with natural gas or
propane (field installed kit) and also comply with California requirements for low NOx
emissions. All units shall have two stage heating.
Controls
Unit shall be completely factory wired with necessary
controls and terminal block for power wiring. Units shall provide an external location for
mounting fused disconnect device. Microprocessor controls shall be provided for all 24
volt control functions. The resident control algorithms shall make all heating, cooling
and/or ventilating decisions in response to electronic signals from sensors measuring
indoor and outdoor temperatures. The control algorithm maintains accurate temperature
control, minimizes drift from set point and provides better building comfort. A
centralized microprocessor shall provide anti-short cycle timing and time delay between
compressors to provide a higher level of machine protection.
Control Options
Inlet Guide Vanes shall be installed on each fan
inlet to regulate capacity and limit horsepower at lower system requirements. When in any
position other than full open they shall pre-spin intake air in the same direction as fan
rotation. The inlet guide vanes shall close when supply fan is off, except in night
setback. The inlet guide vane actuator motor shall be driven by a modulating dc signal
from the unit microprocessor. A pressure transducer shall measure duct static pressure and
modulate the inlet guide vanes to maintain the required supply air static pressure within
a predetermined range.
Variable Frequency Drives (VFDs) shall be factory
installed and tested to provide supply fan motor speed modulation. The VFD shall receive a
2-10 VDC signal from the unit microprocessor based upon supply static pressure and shall
cause the drive to accelerate or decelerate as required to maintain the supply static |
