SYSTEM OPERATION
18
GAS SUPPLY AND PIPING
The furnace rating plate includes the approved furnace gas
input rating and gas types. The furnace must be equipped to
operate on the type of gas applied. This includes any con-
version kits required for alternate fuels and/or high altitude.
CAUTION
To prevent unreliable operation or equipment damage, the
inlet gas supply pressure must be as specified on the unit
rating plate with all other household gas fired appliances
operating.
Inlet gas supply pressures must be maintained within the
ranges specified below. The supply pressure must be con
-
stant and available with all other household gas fired appli
-
ances operating. The minimum gas supply pressure must
be maintained to prevent unreliable ignition. The maximum
must not be exceeded to prevent unit overfiring.
Natural Gas
Minimum: 4.5" w.c.
Maximum: 10.0" w.c.
Propane Gas Minimum: 11.0" w.c. Maximum: 13.0" w.c.
INLET GAS SUPPLY PRESSURE
High Altitude Derate
When this furnace is installed at high altitude, the appropri-
ate High Altitude orifice kit must be applied. This is required
due to the natural reduction in the density of both the gas
fuel and combustion air as altitude increases. The kit will
provide the proper design certified input rate within the spec
-
ified altitude range.
High altitude kits are purchased according to the installation
altitude and usage of either natural or propane gas. Refer
to the product Specification Sheet or the Accessory Matrix in
this Manual for a tabular listing of appropriate altitude rang-
es and corresponding manufacturer’s high altitude (Natural,
Propane gas, and/or Pressure Switch) kits.
Do
not
derate the furnace by adjusting the manifold pressure
to a lower pressure than specified on the furnace rating plate.
The combination of the lower air density and a lower manifold
pressure will prohibit the burner orifice from drawing the prop
-
er amount of air into the burner. This may cause incomplete
combustion, flashback, and possible yellow tipping.
In some areas the gas supplier may artificially derate the
gas in an effort to compensate for the effects of altitude.
If the gas is artificially derated, the appropriate orifice size
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
the gas supplier to determine the proper orifice size.
A different pressure switch may be required at high altitude
regardless of the BTU/ft
3
content of the fuel used. Refer to
the product Specification Sheet or Technical Manual for a
tabular listing of appropriate altitude ranges and correspond-
ing manufacturer’s pressure switch kits.
PROPANE GAS CONVERSION
WARNING
Possible property damage, personal injury or death may
occur if the correct conversion kits are not installed. The
appropriate kits must be applied tot ensure safe and proper
furnace operation. All conversions must be performed by a
qualified installer or service agency.
This unit is configured for natural gas. The appropriate man
-
ufacturer’s propane gas conversion kit, must be applied for
propane gas installations.
**9S9* models using a White-Rodgers 36J22 single stage
valve use LPM-07 LP Conversion Kit.
GAS VALVE
This unit is equipped with a 24 volt gas valve controlled
during furnace operation by the integrated control module.
As shipped, the valve is configured for natural gas. The
valve is field convertible for use with propane gas by using
the appropriate propane gas conversion kit. Taps for mea-
suring the gas supply pressure and manifold pressure are
provided on the valve.
NOTE: The gas supply pressure on White-Rodgers “J”
model 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
the valve itself. This control may be set only to the “ON”
or “OFF” position. Refer to the
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.
