22
50ZH
SMALL PACKAGE PRODUCT AIR-TO-AIR HEAT PUMP
CONSTANT VOLUME APPLICATION
HVAC GUIDE SPECIFICATIONS
SIZE RANGE: 2-1/2 TO 5 TONS, NOMINAL (COOLING)
21,800 TO 52,500 BTUH, NOMINAL
(HEATING)
MODEL NUMBER: 50ZH
PART I - 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 horizontally
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 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
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 factory
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. Basepan shall be made of a single-piece non-corrosive,
composite material.
3. Indoor fan compartment cabinet surfaces shall be in-
sulated with a minimum 1/2 in. thick, flexible insulation,
coated on the air side, with aluminum foil-faced
insulation.
4. Cabinet panels shall be easily removable for servicing.
5. Unit shall have a factory-installed, sloped, non-
corrosive, condensate drain.
6. 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. 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 balanced, and shall
discharge air upwards.
D. Compressor:
Fully hermetic scroll, type with internal and external vibra-
tion 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 bellied to prevent tube
wear.
3. Outdoor coil shall be protected by metal louvered
panels.
F. Refrigerant Components:
1. Fixed orifice feed system.
2. Service gage connections on suction, discharge and
liquid lines.
3. Equipped with liquid line strainers.
4. Equipped with liquid line loss of charge switch.
G. Controls and Safeties:
1. Unit Controls:
a. Unit shall be complete with self-contained low-
voltage control circuit.
b. Defrost board is equipped with 5 minute compressor
time delay protection.
c. Unit shall incorporate an outdoor-coil defrost system
to prevent excessive frost accumulation during
heating duty, and shall be controlled 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 defrost
thermostat is satisfied or shall have a positive
termination time of 10 minutes.
2. Safeties:
Compressor, overtemperature, overcurrent.
H. Operating Characteristics:
1. Unit shall be capable of starting and running at 115°F
ambient outdoor temperature per maximum load criteria
of ARI Standard 240-89.
2. Compressor with standard controls shall be capable of
operation down to 40° F ambient outdoor temperature in
cooling duty.
3. Compressor shall be capable of operation in heating
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.
J. Motors:
1. Compressor motors shall be of the refrigerant-cooled
type with line break thermal and current overload
protection.
Guide specifications
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