254597-YTG-B-0507
28
Unitary Products Group
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).
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-
dant 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
steel for corrosion resistance and allowing minimum mixed
air entering temperature of 25°F. Burners shall be of the
inshot type, constructed of aluminum coated steel and con-
tain air mixture adjustments. All gas piping shall enter the unit
cabinet at a single location through either the side or curb
without any field modifications. Integrated control boards
shall provide timed control of evaporator fan functioning and
burner ignition. Heating section shall be provided with the fol-
lowing minimum protection:
a.
Primary and auxiliary high-temperature limit
switches.
b.
Induced draft motor speed sensor.
c.
Flame roll out switch.
d.
Flame proving controls.
e.
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.
ELECTRIC HEATING SECTION
An electric heating section, with nickel chromium elements,
shall be provided in a range of 5 thru 30 KW, offering two
stages of capacity - 16 KW and above on 208/230 volt heaters
and 20 KW and above on 460 and 575 volt heaters. The heat-
ing section shall have a primary limit control(s) and automatic
reset to prevent the heating element system from operating at
an excessive temperature. The heating section assembly
shall slide out of the unit for easy maintenance and service.
Units with Electric Heating shall be wired for a single point
power supply with branch circuit fusing (where required).
UNIT OPERATING CHARACTERISTICS
a.
Unit shall be capable of starting and running at 125°F
outdoor temperature, exceeding maximum load crite-
ria of ARI Standard 210/240. The compressor, with
standard controls, shall be capable of operation
down to 0°F outdoor temperature. Unit shall be pro-
vided with fan time delay to prevent cold air delivery
before heat exchanger warms up (Gas heat only).
ELECTRICAL REQUIREMENTS
All unit power wiring shall enter unit cabinet at a single factory
provided location and be capable of side or bottom entry, to
minimize roof penetrations and avoid unit field modifications.
Separate side and bottom openings shall be provided for the
control wiring.
