Carrier 48HG014-028 User Manual download pdf (Page 76)

Packaged Rooftop Electric Cooling

Unit with Gas or Electric Heat —

Constant Volume Application

HVAC Guide Specifications

Size Range:

13 to 25 Tons, Nominal (Cooling)

250,000 to 400,000 Btuh, Nominal

(Input Heating) (Gas Units)

12 to 78 kW (Electric Heat)

Carrier Model Numbers:

48HGD, 48HGE, 48HGF, 48HGK,

48HGL, 48HGM, 50HG

Part 1 — General

1.01 SYSTEM DESCRIPTION

Unit is an outdoor rooftop mounted, electrically

controlled heating and cooling unit utilizing scroll

hermetic compressors with crankcase heaters for

cooling duty and gas combustion or electric heat

for heating duty. Supply air shall be discharged

downward or horizontally, as shown on contract

drawings.

1.02 QUALITY ASSURANCE

A. Unit shall comply with minimum requirements of

ASHRAE 90.1-2001 Energy Efficiency Standards.

B. Unit shall be rated in accordance with ARI

Standards 270 and 340/360 and all units shall be

designed in accordance with UL Standard 1995.

C. Unit shall be designed to conform to ASHRAE 15.

D. Unit shall be UL and UL, Canada tested and

certified in accordance with ANSI Z21.47 Standards

as a total package.

E. Roof curb shall be designed to conform to NRCA

Standards.

F. Insulation and adhesive shall meet NFPA 90A require-

ments for flame spread and smoke generation.

G. Unit casing shall be capable of withstanding

500-hour salt spray exposure per ASTM B117

(scribed specimen).

H. Unit shall be manufactured in a facility registered to

ISO 9001:2000.

1.03 DELIVERY, STORAGE, AND HANDLING

Unit shall be stored and handled per manufacturer’s

recommendations.

Part 2 — Products

2.01 EQUIPMENT (STANDARD)

A. General:

The unit shall be a factory assembled, single-piece

heating and cooling unit. Contained within the unit

enclosure shall be all factory wiring, piping, controls,

refrigerant charge (R-22), and special features

required prior to field start-up.

B. Unit Cabinet:

1. Constructed of galvanized steel (G90 — 1.8 oz.

of zinc per square foot [550 grams per square

meter] of sheet metal), bonderized and primer-

coated on both sides and coated with a baked

polyester thermosetting powdercoating finish

on the outer surface.

2. Indoor blower compartment interior surfaces

shall be insulated with a minimum

-in. thick,

1 lb density fiberglass insulation. Fiberglass

insulation shall be bonded with a thermosetting

resin (8 to 12% by weight nominal, phenol

formaldehyde typical), and coated with an

acrylic or other material that meets the NFPA

90 flame retardance requirements and has an

‘‘R’’ Value of 3.70. Aluminum foil-faced fiber-

glass insulation shall be used in the gas heat

compartment.

3. Cabinet panels shall be hinged with stainless

steel hinges. Panels shall have minimum

-in.

thick, 1.5-lb. density insulation. Hinged access

panels for the filter, compressors, evaporator

fan, and control box areas. Filter hinged access

panels permit tool-less entry for changing fil-

ters. Each external hinged access panel shall be

double-wall construction and permanently

attached to the rooftop unit. Panels shall also

include tiebacks.

4. Filters shall be accessible through a hinged

access panel.

5. Holes shall be provided in the base rails (mini-

mum 14 gage) for rigging shackles and level

travel and movement during overhead rigging

operations.

6. Fork lift slots shall be available from two sides of

the unit (end and side).

7. Unit shall contain a sloped drain pan, to pre-

vent standing water from accumulating. Pan

shall be fabricated of epoxy powder coated

steel.

C. Fans:

1. Indoor blower (evaporator fan):

a. Centrifugal supply air blower shall have

pillow-block ball bearings and adjustable belt

drive. Blower assembly shall slide out of unit

for servicing.

b. Fan wheel shall be made from steel with a

corrosion resistant finish. It shall be a

dynamically balanced, double-inlet type with

forward-curved blades.

c. The indoor fan system (blower wheels,

motors, belts, and both bearings) shall slide

out for easy access.

2. Condenser fans shall be of the direct-driven

propeller type, with corrosion-resistant blades

riveted to corrosion-resistant steel supports.

They shall be dynamically balanced and dis-

charge air upwards. Condenser fan motors shall

be totally enclosed and be of a shaft down

design.

Guide specifications — 48/50HG014-028

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