Guide specifications
Packaged Rooftop Air-to-Air Heat Pump
Constant Volume Application
HVAC Guide Specifications
Size Range:
2 to 5 Tons, Nominal (Cooling)
23,800 to 57,000 Btuh (Heating)
Carrier Model Number:
50HX
Part 1 — General
1.01 SYSTEM DESCRIPTION
Outdoor package, electrically controlled, air-to-air heat
pump utilizing a scroll compressor for heating and
cooling duty. Unit shall discharge supply air horizon-
tally or vertically as shown on contract drawings.
1.02 QUALITY ASSURANCE
A. Unit shall be rated in accordance with ARI Standards
210/240 and 270 latest revisions. Designed in ac-
cordance with UL Standard 1995.
B. Unit shall be designed to conform to ASHRAE 15.
C. Unit shall be UL listed and UL, Canada, certified as a
total package for safety requirements.
D. Insulation and adhesive shall meet NFPA 90A require-
ments for flame spread and smoke generation.
E. Unit shall be manufactured in a facility registered to
ISO 9002 (International Standards Organization) Manu-
facturing quality standard.
1.03 DELIVERY, STORAGE, AND HANDLING
Unit shall be stored and handled per manufacturer’s
recommendations.
Part 2 — Products
2.01 EQUIPMENT
A. General:
Factory-assembled, single piece, air-to-air heat pump.
Contained within the unit enclosure shall be all fac-
tory wiring, piping, controls, and refrigerant charge
(R-22).
B. Unit Cabinet:
1. Unit cabinet shall be constructed of phosphated,
bonderized, zinc-coated, prepainted steel, capable
of withstanding 500 hours in salt spray, Federal
Test Method Std. No. 141 (Method 6061).
2. Indoor fan compartment cabinet surfaces shall
be insulated with a minimum
1
⁄
2
in. thick, flexible
fiberglass insulation, coated on the air side, with
aluminum foil-faced fiberglass insulation.
3. Cabinet panels shall be easily removable for
servicing.
4. Unit shall have a factory-installed sloped, non-
corrosive condensate drain.
5. Unit insulation conforms to ASHRAE 62P.
6. Unit shall have a single-piece top cover.
C. Fans:
1. Indoor Blower (Indoor Fan):
a.
Fan shall be 3-speed (sizes 024-042) or vari-
able speed (sizes 048 and 060), direct drive
as shown on the equipment drawings.
b.
Fan wheel shall be made from steel, be double-
inlet type. It shall have forward-curved blades
with a corrosion-resistant finish and shall be
dynamically balanced.
2. Outdoor fan shall be of the direct-driven propeller
type with aluminum blades, riveted to corrosion-
resistant steel spiders. It shall be dynamically bal-
anced, and shall discharge air upwards and
horizontally.
D. Scroll Compressor:
Fully hermetic scroll type with internal and external
vibration isolation.
E. Coils:
1. Indoor and outdoor coils shall have aluminum-
plate fins mechanically bonded to seamless cop-
per tubes with all joints brazed.
2. Tube sheet openings shall be belled to prevent tube
wear.
F. Refrigerant Components:
Acutrol™ feed system.
G. Controls and Safeties:
1. Unit Controls:
a.
Unit shall be complete with self-contained low-
voltage control circuit.
b.
Unit shall incorporate an outdoor-coil defrost
system to prevent excessive frost accumula-
tion during heating duty, and shall be con-
trolled as follows:
1) Defrost shall be initiated on the basis of
time and coil temperature.
2) A 30/50/90 minute timer shall activate
defrost cycle only if coil temperature is
low enough to indicate a heavy frost
condition.
3) Defrost cycle shall terminate when de-
frost thermostat is satisfied or shall have
a positive termination time of 10 minutes.
2. Safeties:
a.
Compressor, overtemperature, overcurrent.
b.
Refrigerant lines — strainer, loss-of-charge
switch.
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