Carrier 50YX - Manual (Page 18)

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Packaged Rooftop Air-to-Air Heat Pump
Constant Volume Applications
HVAC Guide Specifications
Size Range: IV 2 to 5 Tons, Nominal (Cooling)
18,000 to 60,000 Btuh, Nominal
(Heating)
Carrier Model Number: 50YX
Part 1 — General
1.01 SYSTEM DESCRIPTION
Outdoor package, electrically controlled, air-to-air heat
pump utilizing a scroll compressor for heating and cool­
ing duty. Unit shall discharge supply air horizontally as
shown on contract drawings.
1.02 QUALITY ASSURANCE
A. Unit shall be rated in accordance with ARI Standards
210, 240, and 270. Designed in accordance with UL
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 NFPA 90A require­
ments for flame spread and smoke generation
1.03 DELIVERY, STORAGE, AND HANDLING
A. 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.
2. Indoor-fan compartment interior cabinet surfaces
shall be insulated with a minimum Vz-in thick, flex­
ible fiberglass insulation, coated on the air side. Alu­
minum foil-faced fiberglass insulation shall be used
in the heating compartment
3. Cabinet panels shall be easily removable for
servicing.
4 Unit shall have a factory-installed condensate drain.
C. Fans:
1. Indoor Blower (Indoor Fan):
a. Fan shall be 2- or 3-speed direct drive as shown
on the equipment drawings
b. Fan wheel shall be made from steel, be double­
inlet type with forward-curved blades with a
corrosion-resistant finish and shall be dynam­
ically balanced.
2. Qutdoor (condenser) fan shall be of the direct-
driven propeller type with aluminum blades, riv­
eted to corrosion-resistant steel spiders, shall be
dynamically balanced, and shall discharge air ver­
tically upwards.
D Compressor
1 Fully hermetic scroll compressor with internal and
external vibration isolation
E Coils:
1. Indoor and outdoor coils shall have aluminum-
plate fins mechanically bonded to seamless copper
tubes with all joints brazed
2. Tube sheet openings shall be belled to prevent tube
wear
F. Refrigerant Components.
1. Thermostatic expansion valve
2 Reversing valve.
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 de­
frost cycle only if coil temperature is low
enough to indicate a heavy frost condition
3) Defrost cycle shall terminate when defrost
thermostat is satisfied or shall have a pos­
itive termination time of 10 minutes
c. Compressor shall be prevented from restart­
ing for a minimum of 5 minutes after shut­
down
2. Safeties:
a. Compressor, overtemperature, overcurrent.
H. Qperating Characteristics:
1. Unit shall be capable of starting and running at
115 F ambient outdoor temperature per maximum
load criteria of ARI Standard 210/240
2. Compressor with standard controls shall be capa­
ble of operation down to 55 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 heat­
ers indicated in Section K, Special Features.
I Electrical Requirements:
All unit power wiring shall enter unit cabinet at a sin­
gle location. Separate power supply is not required for
electric heaters when accessory single point box is used.
J. Motors:
1. Compressor motors shall be of the refrigerant-
cooled type with line break thermal and current
overload protection
2. All fan motors shall have permanently lubricated
bearings and inherent automatic reset thermal over­
load protection.
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