Carrier 48SS - Manual (Page 6)

Factory-installed options
Unit with base rail
provides holes for rigging and handling
as well as an elevated mounting frame that gives additional
structural support for horizontal installations
Downflow option unit is shipped from factory configured
for vertical ductwork connection Unit is equipped with
base rail.
Field-installed accessories
Factory-assembled roof curbs
are designed for use on
downflow discharge applications Heavy gage, galvanized
steel construction provides one-piece support The curb com­
plies with the standards of the NRCA (National Roofing Con­
tractors Association) A wood nailing strip is provided for
attaching the roofing to the curb
Modulating economizers
are available for downflow or
horizontal discharge applications
The economizers adjust their outdoor- and return-air damp­
ers to economically blend cooler outdoor air with warmer
return air for comfort cooling. This process reduces energy
costs and extends equipment life by allowing the use of
outdoor air to supply “free” cooling when conditions are
favorable
Modulating economizers have a mixed-air controller that
provides for full-range modulation of the outdoor- and return-
air dampers The enthalpy control selects the suitable outdoor-
air quality for “free” cooling operation by measuring the
outdoor-air dry bulb temperature and humidity mix Mod­
ulating economizers also have an adjustable, motor-mounted,
minimum-position potentiometer and a compressor lockout
switch The motor operates through the unit 24-v low-voltage
control circuit.
Constant ventilation is recommended for light commer­
cial application when the conditioned space is occupied
Manual outdoor-air damper
provides for minimum out­
door air and is manually adjustable This device closes au­
tomatically whenever the evaporator fan is not operating
Two-position damper
allows outside air to enter the build­
ing when the indoor fan is energized When enthalpy con­
trol detects that outside air is suitable for cooling, outdoor-
air damper opens fully and indoor-air damper closes, allowing
outside air to enter building
Thermostat and subbase
provide heating and cooling unit
control The subbase provides system and fan switching at
the thermostat location
Carrier electronic programmable thermostats
pro
vide 2-stage heating and 2-stage cooling control with remote
communication ability
Low-ambient kit (Motormaster® II device)
allows the
use of mechanical cooling down to outdoor ambient tem­
peratures as low as 0° F
UNIT WITH OPTIONAL BASE RAIL
Solid-state Time Guard® device protects compressor by
preventing short cycling.
Crankcase heater
warms crankcase oil to reduce refriger­
ant migration and ensure proper compressor lubrication. (Rec­
ommended on 208/230-v single-phase units in sizes 024-
042 only)
High- and Tow-pressure switches
provide additional safety
features and protect the unit from running at unsuitable
pressures.
Filter rack
features easy installation, serviceability, and high
filtering performance
Lifting bracket kit
provides attachment points for rigging
straps The kit is not required when unit is equipped with an
optional base rail or downflow application.
The natural-to-propane conversion kit
allows for con­
version from natural gas to liquid propane
Flexible duct kit
consists of 2 flexible UL-listed (Under­
writers’ Laboratories) ducts The duct construction includes
vapor barrier and 1-in fiberglass insulation The ‘K’ factor is
0 23 Each duct has a square-to-round snap adapter for at­
tachment to the accessory roof curb on one end, and a round
clamp collar for attachment to the accessory concentric dif­
fuser box on the other end
Concentric diffuser box is aerodynamically designed and
equipped with a combination 4-way supply and center re­
turn diffuser The box is designed for use with accessory
flexible ducts and roof curbs to provide an easily installed
concentric system A special core is provided with the dif­
fuser box to provide even 4-way air distribution.