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15.4 Gas Piping
The gas manifold extends through the side of the
control cabinet for models XT-112 - XT-130. The
factory piping terminates with a female pipe
connection in the manual gas valve. The manual
main gas shutoff valve is shipped loose for field
installation. A union must also be installed (supplied
by others) between the supplied manual gas valve
main and the first tee pipe. Be sure that the fuel
supply pipe connected at this point is large enough to
ensure the proper gas flow 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 no piping restricts
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.
15.5 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.
15.5.1 Manifold Inlet Gas Pressure
The pressure 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.
15.5.2 Burner Gas Pressure
A pressure tap is used to measure negative airflow at
the burner and to set high fire gas pressure. On air
handlers equipped with a M611 modulating valve, the
pressure tap is located on a tee between the M611
valve and the burner. See Page 39, Figure 22 and
Page 68, Figure 37. On air handlers equipped with
the MR212 modulating valve, the pressure tap could
be located on the downstream side of the MR212
valve, on a T-fitting coming off the outlet pressure tap
on the MR212 valve or between the MR212 valve
and the burner. See Page 39, Figure 23 and Page 67 ,
Figure 35.
FIGURE 22: Plug Tapping (XT-112)
Modulating Valve
Manual Gas Valve (Burner)
FIGURE 23: Plug Tapping (XT-115 - XT-130)
Modulating Valve
Manual Gas Valve (Burner)
Plugged Taping
15.6 Line Pressure Test - Leak Testing
The air handler and its individual shut-off valve must
be disconnected from the gas supply piping systems
during any pressure testing of that system at test
pressures in excess of 14 in wc (34.9 mbar). The air
handler must be isolated from the gas supply piping
system by closing its individual manual gas valve that
is located immediately upstream of the safety shut-off
gas valve.
SECTION 15: G
AS
Plugged Taping
To Measure Burner Pressure
Burner
Burner
P
IPING
39
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