4000-SERIES INSTALLATION, OPERATION AND SERVICE MANUAL
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18.3 Gas Piping
The gas manifold connection extends through the
side of the control enclosure for vertical equipment
and through the bottom for horizontal equipment. The
factory piping terminates with a male pipe connection
in the primary gas valve. Be sure that the fuel supply
pipe connected at this point is large enough to
ensure the proper volume and line pressure at the
inlet of the air handler. The piping must comply with:
United States: Refer to NFPA 54/ANSI Z223.1 - latest
revision, National Fuel Gas Code.
Canada: Refer to CSA B149.1 - latest revision,
Natural Gas and Propane Installation Code.
Gas supply piping must conform to best building
practices and local codes. During installation of the
gas piping, be sure that piping does not restrict
accessibility to the air handler or its removable
access doors.
Lockable manual shut-off valve must be added by the
installer in compliance with Occupational Safety and
Health Administration (OSHA) regulations.
18
.4 Pressure Test Ports
There are 1/8"(3.2 mm) and 1/4"(6.4 mm) pressure
test ports located on the manifold. The test ports are
available to measure the manifold inlet gas pressure
and the burner gas pressure during burner setup.
18.4.1 Manifold Inlet Gas Pressure
The pressure test port for measuring manifold inlet
pressure is located on the inlet side of the first safety
shutoff valve. Refer to the unit rating plate for the
acceptable inlet gas pressure.
18.4.2 Burner Gas Pressure
A pressure tap is used to measure negative pressure
at the burner (fan only, gas valves closed) and to set
high fire gas pressure regulating (gas valves open).
Air handlers are equipped with a modulating/
regulating valve (MRV). The pressure tap is located
on the downstream side of the MRV.
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