Carrier 48NLT - Manual (Page 7)

IN testing of the piping systems when test pressure in excess
of 0.5 psig. Pressure test the gas supply piping system at
pressures equal to or less than 0.5 psig. The unit heating
section must be isolated from the gas piping system by clos­
ing the external main manual shutoff valve and slightly open­
ing the ground-joint union.
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 au­
thority having jurisdiction, black iron pipe shall be in­
stalled at the gas valve and shall extend a minimum of
2 in. outside the unit casing.
Size "A"
Small Cabinet NLT018-NET042 20V2 in.
Large Cabinet NHT036-NVT060 25V2 in.
Fig. 8 — Location of Coii Area Not to be Drilled
5. Install an accessible, external, manual main shutoff valve
in gas supply pipe within 6 ft of heating section.
6. Install ground-joint union close to heating section be­
tween unit manual shutoff and external manual main shut­
off valve.
7. Pressure-test all gas piping in accordance with local and
national plumbing and gas codes before connecting pip­
ing to unit.
NOTE; Pressure test the gas supply system after the gas
supply piping is connected to the gas valve. The supply
piping must be disconnected from the gas valve during the
A WARNING
Never use a match or other open flame when checking
for gas leaks. Never purge gas line into combustion
chamber. Failure to follow this warning could result in
an explosion causing personal injury or death.
8. Check for gas leaks at the field-installed and factory-
installed gas lines after all piping connections have been
completed. Use soap-and-water solution (or method spec­
ified by local codes and/or regulations).
Step 8 — Install Duct Connections — The unit
has duct flanges on the supply- and return-air openings on
the side and bottom of the unit. See Fig. 2 and 3 for con­
nection sizes and locations.
NOTE: The design and installation of the duct system must
be in accordance with the standards of the NFPA for instal­
lation of nonresidence-type air conditioning and ventilating
systems, NFPA No. 90A orresidence-type, NFPA No. 90B;
and/or local codes and 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. The unit is shipped in vertical configuration. To convert
unit to horizontal application, remove side duct covers,
save screws and install the covers on bottom duct
openings.
2. Select and size ductwork, supply-air registers and return-
air grilles according to ASHRAE (American Society of
Heating, Refrigeration and Air Conditioning Engineers)
recommendations.
A CAUTION
When drilling the duct-system fastening holes into the
side of the unit instead of the unit duct flanges, use ex­
treme care to avoid puncturing the coil or coil tubes.
See Fig. 8.