Carrier 48NHT024 - Duct Connections; Electrical Connections

A CAUTION
Unstable operation may occur when the gas valve and
manifold assembly are forced out of position while con¬
necting improperly routed rigid gas piping to the gas
valve. Use a backup wrench when making connection to
avoid strain on, or distortion of, the gas control piping.
A CAUTION
If a flexible conductor is required or allowed by the
authority having jurisdiction, black iron pipe shall be
installed at the gas valve and extend a minimum of
2-ins. outside the unit casing.
A WARNING
Never use a match or other open flame when checking
for gas leaks. Never purge gas line into combustion
chamber. Failure to adhere to this warning could result
in an explosion.
8. Check for gas leaks at all field-installed and factory-
installed gas lines after all piping connections have
been completed. Use soap-and-water solution (or
method specified by local codes and/or regulations).
Step 5—Duct Connections
Model 48N has duct flanges on the supply- and return-air
openings on the side and bottom of the unit. See Figs. 2 and
3 for connection sizes and locations.
NOTE: The design and installation of the duct system must
be in accordance with the standards of the National Fire
Protection Association for installation of nonresidence-type
air conditioning and ventilating systems, NFPA No. 90A or
residence-type, NFPA No. 90B; and/or local codes and
ordinances.
Adhere to the following criteria when selecting, sizing, and
installing the duct system:
1. R emove appropriate panels from unit to obtain either
side or bottom discharge. If models 48NLT018 thru
48NMT042 are installed in horizontal discharge appli¬
cations, remove side duct covers, save screws, and
install the covers on bottom duct openings. For models
48NHT036 thru 48NHT060 remove either side or bot¬
tom duct covers as needed and discard.
2. S elect and size ductwork, supply-air registers, and
return-air grilles according to ASHRAE recom¬
mendations.
A CAUTION
When the duct-system fastening holes are being drilled
into side of Model 48N instead of the unit duct flanges,
use extreme care to avoid puncturing the coil or coil
tubes.
3. Use flexible transition between rigid ductwork and unit
to prevent transmission of vibration. The transition
may be screwed or bolted to duct flanges. Use suitable
gaskets to ensure weather and airtight seal.
4. Install external, field-supplied air filter(s) in return-air
ductwork where it is easily accessible for service. Rec¬
ommended filter sizes are shown in Tables 2 thru 7.
5. Size all ductwork for maximum required airflow (either
heating or cooling) for unit being installed. Avoid
abrupt duct size increases or decreases.
6. Adequately insulate and weatherproof all ductwork
located outdoors. Insulate ducts passing thru uncondi¬
tioned space, and use vapor barrier in accordance with
latest issue of SMACNA and ACC A minimum installa¬
tion standards for heating and air conditioning sys¬
tems. Secure all ducts to building structure.
7. Flash, weatherproof, and vibration-isolate all openings
in building structure in accordance with local codes and
good building practices.
Step 6—Electrical Connections
1. Make all electrical connections in accordance with
National Electrical Code ANSI/NFPA 70-1987 and
local electrical codes governing such wiring. In Canada,
all electrical connections must be in accordance with
CSA standard C22.1 Canadian Electrical Code Part 1
and applicable local codes. Refer to Unit Wiring
Diagram.
2. Use only copper conductor for connections between
field-supplied electrical disconnect switch and unit. DO
NOT USE ALUMINUM WIRE.
3. Ensure that high-voltage power to unit is within oper¬
ating voltage range indicated on unit rating plate. On
3-phase units, ensure that phases are balanced within
2%. Consult local power company for correction of
improper voltage and/or phase balance.
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