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254599-YTG-C-0807
22 Unitary Products Group
insulated with a minimum 1/2” thick insulation, coated on the
airside. Aluminum foil faced insulation shall be used in the
furnace compartment and be fastened with ridged fasteners
to prevent insulation from entering the air stream. Cabinet
panels shall be “large” size, easily removable for servicing
and maintenance. Full perimeter base rails shall be provided
to assure reliable transit of equipment, overhead rigging and
proper sealing on roof curb applications. Disposable 1" filters
shall be furnished and be accessible through a removable
access door, sealed airtight. Units filter track shall be
designed to accommodate either 1” or 2” filters. Fan
performance measuring ports shall be provided on the
outside of the cabinet to allow accurate air measurements of
evaporator fan performance without removing panels or
creating air by-pass of the coils. Condensate pan shall be
internally sloped and conform to ASHRAE 62-89 self-draining
standards. Condensate connection shall be a minimum of 3/
4” I.D. female and be a ridged mount connection.
INDOOR (EVAPORATOR) FAN ASSEMBLY
The indoor fan shall be direct drive, multi-speed, or a factory
installed belt drive assembly that includes an adjustable pitch
motor pulley. Job site selected brake horsepower (B.H.P.)
shall not exceed the motors nameplate horsepower rating,
plus the service factor. Units shall be designed not to operate
above service factor. Fan wheel shall be double-inlet type
with forward-curved blades, dynamically balanced to operate
smoothly throughout the entire range of operation. Airflow
design shall be constant air volume. Bearings shall be sealed
and permanently lubricated for longer life and no mainte-
nance.
OUTDOOR (CONDENSER) FAN ASSEMBLY
The outdoor fan shall be of the direct-driven propeller type,
discharge air vertically, have aluminum blades riveted to a
corrosion resistant steel spider bracket and shall be dynami-
cally balanced for smooth operation. The outdoor fan motor
shall be totally enclosed with permanently lubricated bear-
ings, internally protected against overload conditions and
staged independently.
REFRIGERANT COMPONENTS
Compressor:
a. Shall be internally protected with internal high-pres-
sure relief and over temperature protection.
b. Shall have internal spring isolation and sound muf-
fling to minimize vibration and noise, and be exter-
nally isolated on a dedicated, independent
mounting.
Coils:
a. Evaporator and condenser coils shall have alumi-
num plate fins mechanically bonded to seamless
internally enhanced copper tubes with all joints
brazed. Special Phenolic coating shall be available
as a factory option.
b. Evaporator and Condenser coils shall be of the
direct expansion, draw-thru, design.
Refrigerant Circuit and Refrigerant Safety Components shall
include:
a. Thermal expansion devices (TXV’s).
• DF072 uses a fixed orifice distributor.
b. Filter drier/strainer to eliminate any moisture or for-
eign matter.
c. Accessible service gage connections on both suc-
tion and liquid lines to charge, evacuate, and mea-
sure refrigerant pressure during any necessary
servicing or troubleshooting without losing charge.
d. The refrigeration system shall provide at least 15°F
of sub-cooling at design conditions.
UNIT CONTROLS
a. Unit shall be complete with self-contained low-volt-
age control circuit protected by a resetable circuit
breaker on the 24-volt transformer side.
b. Unit shall incorporate a lockout circuit which pro-
vides reset capability at the space thermostat or
base unit, should any of the following standard
safety devices trip and shut off compressor.
c. Loss-of-charge/Low-pressure switch.
d. High-pressure switch.
e. Freeze-protection thermostat, evaporator coil.
f. If any of the above safety devices trip, a LED (light-
emitting diode) indicator shall flash a diagnostic
code that indicates which safety switch has tripped.
g. Unit shall incorporate “AUTO RESET” compressor
over temperature, over current protection.
h. Unit shall operate with conventional thermostat
designs and have a low voltage terminal strip for
easy hook-up.
i. Unit control board shall have on-board diagnostics
and fault code display.
j. Standard controls shall include anti-short cycle and
low voltage protection, and permit cooling operation
down to 0°F.
k. Control board shall monitor each refrigerant safety
switch independently.
l. Control board shall retain last 5 fault codes in non
volatile memory, which will not be lost in the event of
a power loss.
GAS HEATING SECTION (SINGLE OR 2 STAGE)
Shall be designed with induced draft combustion with post
purge logic, energy saving direct spark ignition, and redun-
da
nt main gas valve. Venter wheel shall be constructed of
stainless steel for corrosion resistance. The heat exchanger
shall be of the tubular type, constructed of T1-40 aluminized