GM9S80 Service Manual
SYSTEM OPERATION
21
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High altitude kits are purchased according to the installation
altitude and usage of either natural or propane gas. Refer
a tabular listing of appropriate altitude ranges and corre-
sponding manufacturer’s high altitude (Natural, Propane
gas, and/or Pressure Switch) kits.
Do not derate the furnace by adjusting the manifold pressure
The combination of the lower air density and a lower manifold
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er amount of air into the burner. This may cause incomplete
must be determined based upon the BTU/ft
3
content of the
derated gas and the altitude. Refer to the National Fuel Gas
Code, NFPA 54/ANSI Z223.1, and information provided by
regardless of the BTU/ft
3
content of the fuel used. Refer to
tabular listing of appropriate altitude ranges and correspond-
ing manufacturer’s pressure switch kits.
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ufacturer’s propane gas conversion kit, must be applied for
propane gas installations.
• Single-stage 80% furnace models using a Honeywell
VR8215 single stage valve or a White-Rodgers 36J22
use LPT-03 LP Conversion Kit.
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This unit is equipped with a 24 volt gas valve controlled
during furnace operation by the integrated control module.
the appropriate propane gas conversion kit. Taps for mea-
suring the gas supply pressure and manifold pressure are
provided on the valve.
gas valve, used on single stage furnaces, can be checked
with a gas pressure test kit (Part #0151K00000S) available
through our authorized distributors.
The gas valve has a manual ON/OFF control located on
Lighting Instructions Label
or the “Putting the Furnace Into Operation” section of this
manual or the installation instructions for use of this control
during start up and shut down periods.
The gas piping supplying the furnace must be properly sized
and length of the run. The gas line installation must comply
with local codes, or in their absence, with the latest edition of
the National Fuel Gas Code, NFPA 54/ANSI Z223.1.
Length of Nominal Black Pipe Size
Pipe in Feet 1/2" 3/4" 1" 1 1/4" 1 1/2"
10 132 278 520 1050 1600
20 92 190 350 730 1100
30 73 152 285 590 980
40 63 130 245 500 760
50 56 115 215 440 670
60 50 105 195 400 610
70 46 96 180 370 560
80 43 90 170 350 530
90 40 84 160 320 490
100 38 79 150 305 460
CFH =
(Pressure 0.5 psig or less and pressure drop of 0.3" W.C.; Based on 0.60 Specific
Gravity Gas)
BTUH Furnace Input
Heating Value of Gas (BTU/Cubic Foot)
To connect the furnace to the building’s gas piping, the in-
staller must supply a ground joint union, drip leg, manual
In some cases, the installer may also need to supply a tran-
The following stipulations apply when connecting gas pip-
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tions to the furnace.
1.
piping.
2. Use pipe joint compound on male threads only. Pipe
joint compound must be resistant to the action of the
fuel used.