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Packaged Rooftop Cooling Unit with
Electric Heat Option — Constant Volume
Application
HVAC Guide Specifications
Size Range: 17.6 to 35.9 kW (5.0 to 10.2 Tons)
Nominal Cooling
Carrier Model Number: 50TFF
Part 1 — General
1.01 SYSTEM DESCRIPTION
Outdoor rooftop- or slab-mounted, electrically con-
trolled cooling unit with optional heat utilizing a her-
metic compressor for cooling duty and electric
resistance coils for heating duty. Unit shall discharge
supply air vertically or horizontally as shown on con-
tract drawings.
1.02 QUALITY ASSURANCE
A. Unit shall be rated in accordance with ARI Standards
210/240 or 360 and 270 (U.S.A.).
B. Unit shall be designed to conform to ASHRAE 15,
latest revision, and in accordance with UL 1995.
(U.S.A. Standards).
C. Roof curb shall be designed to conform to NRCA
Standards (U.S.A.).
D. Insulation and adhesive shall meet NFPA 90A
requirements (U.S.A. Standard) for flame spread and
smoke generation.
E. Unit casing shall be capable of withstanding Federal
test method (U.S.A. Standard) Standard ASTM B117
500-hour salt spray test.
F. Units shall be designed in accordance with
ISO 9001:2000, and shall be manufactured in a
facility registered to ISO 9001:2000.
1.03 DELIVERY, STORAGE, AND HANDLING
Unit(s) shall be stored and handled per manufacturer’s
recommendations.
Part 2 — Products
2.01 EQUIPMENT (STANDARD)
A. General:
Factory-assembled, single-piece cooling unit with
optional heat. Contained within the unit enclosure
shall be all factory wiring, piping, controls, refrigerant
charge (R-22), and special features required prior to
field start-up.
B. Unit Cabinet:
1. Unit cabinet shall be constructed of galvanized
steel, bonderized and coated with a baked
enamel finish on all externally exposed surfaces.
2. Evaporator fan cabinet interior shall be insulated
with a minimum 13 mm (
1
/
2
-in.) thick 1 lb den-
sity neoprene coated, flexible fiberglass insula-
tion coated on the air side.
3. Cabinet panels shall be easily removable for
servicing.
4. Holes shall be provided in the base rails for rig-
ging shackles to facilitate overhead rigging, and
forklift slots shall be provided to facilitate
maneuvering.
5. Unit shall have a factory-installed, sloped con-
densate drain pan made of a non-corrosive
material, providing a minimum 19 mm (
3
/
4
-in.)
connection with both vertical and horizontal
drains and shall comply with ASHRAE 62.
6. Unit shall have factory-installed filter access
panel to provide filter access with tool-less
removal.
7. Unit shall have standard thru-the-bottom power
connection capability.
C. Fans:
1. Indoor blower (evaporator fan) shall be belt-
driven, double inlet, forward-curved centrifugal
type. Belt drive shall include an adjustable-pitch
motor pulley.
2. Indoor blower (evaporator-fan) shall be made
from steel with a corrosion-resistant finish and
shall be dynamically balanced.
3. Bearings shall be of the sealed, permanently
lubricated, ball-bearing type for longer life and
lower maintenance.
4. Condenser fan shall be of the direct-driven pro-
peller type and shall discharge air vertically.
5. Condenser fan shall have aluminum blades riv-
eted to corrosion-resistant steel spiders and shall
be dynamically balanced.
D. Compressor(s):
1. Reciprocating or scroll type fully hermetic type,
internally protected.
2. Factory rubber-mounted and internally spring
mounted for vibration isolation.
3. On independent mounting circuits (008-014).
E. Coils:
1. Condenser coils shall have aluminum plate fins
mechanically bonded to enhanced copper tubes
with all joints brazed.
2. Tube sheet openings shall be belled to prevent
tube wear.
3. Evaporator coil shall be of the full face active
design.
F. Refrigerant Components:
Refrigerant circuit components shall include:
1. Refrigerant feed system.
2. Refrigerant filter drier.
3. Service gage connections on suction, discharge,
and liquid line.
G. Filter Section:
1. Standard filter section shall consist of factory-
installed low-velocity, throwaway 51 mm (2-in.)
thick fiberglass filters of commercially available
sizes.
2. Filter face velocity shall not exceed 1.64 m/s
(320 fpm) at nominal airflows.
3. Filter section shall use only one size filter.
4. Filters shall be accessible through an access
panel with ‘‘no-tool’’ removal.
H. Controls and Safeties:
1. Unit Controls:
Unit shall be complete with self-contained low-
voltage control circuit.
Guide specifications
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