Guide specifications
Packaged Rooftop Air-to-Air Heat Pump
Constant Volume Application
HVAC Guide Specifications
Size Range: 1
1
⁄
2
to 5 Tons, Nominal (Cooling)
18,000 to 60,000 Btuh, Nominal
(Heating)
Carrier Model Number: 50HS
Part 1 — General
1.01 SYSTEM DESCRIPTION
Outdoorpackage, electrically controlled, air-to-airheat
pump utilizing a reciprocating or scroll compressor
for heating and cooling duty. Unit shall discharge sup-
ply air horizontally or vertically as shown on contract
drawings.
1.02 QUALITY ASSURANCE
A. Unit shall be rated in accordance with ARI Standards
210/240-89, and 270-84. Designed in accordance
with UL Standard 1995.
B. Unit shall be designed to conform to ASHRAE 15.
C. Unit shall be UL listed and CSA certified as a total
package for safety requirements.
D. Insulation and adhesive shall meet NFPA90Arequire-
ments for flame spread and smoke generation.
1.03 DELIVERY, STORAGE, AND HANDLING
Unit shall be stored and handled per manufacturer’s
recommendations.
Part2—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.
2. Indoor fan compartment cabinet surfaces shall be
insulated with a minimum
1
⁄
2
in. thick, flexible fi-
berglass insulation, coated on the air side, with alu-
minum foil-faced fiberglass insulation.
3. Cabinet panels shall be easily removable for
servicing.
4. Unit shall have a factory-installed condensatedrain.
5. Unit insulation conforms to ASHRAE 62P.
C. Fans:
1. Indoor Blower (Indoor Fan):
a. Fan shall be 2- or 3-speed, direct drive as
shown on the equipment drawings.
b. Fanwheel shall be made from steel,bedouble-
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. Compressor:
1. Fully hermetic type with internal and external vi-
bration isolation.
2. All reciprocating compressors are equipped with
crankcase heaters.
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:
1. Fixed orifice metering device feed system
2. Accumulator
G. Controls and Safeties:
1. Unit Controls:
a. Unit shallbecomplete 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.
H. Operating Characteristics:
1. Unit shall be capable of starting and running at
115 F ambient outdoor temperature per maxi-
mum load criteria of ARI Standard 240-89.
2. Compressor with standard controls shall be ca-
pable of operation down to 40 F ambient outdoor
temperature in cooling duty.
3. Compressor shall be capable of operation in heat-
ing duty down to –20 F ambient outdoor-air
temperature.
4. Unit shall be capable of simultaneous heating duty
and defrost cycle operation when using electric
heaters indicated in Section K, Special Features.
5. Compressors will be prevented from restarting for
a minimum of 5 minutes after shutdown.
I. Electrical Requirements:
All unit power wiring shall enter unit cabinet at a single
location.
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