Installation Instructions

27
Inlet gas supply pressures must be maintained within the ranges
specified in the adjacent table. The supply pressure must be
constant 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.
HIGH ALTITUDE DERATE
When this furnace is installed at high altitude, the appropriate
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 specified altitude
range.
High altitude kits are purchased according to the installation
altitude and usage of either natural or propane gas. Consult the
furnace Specification Sheet for appropriate 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 pres-
sure will prohibit the burner orifice from drawing the proper
amount of air into the burner. This may cause incomplete com-
bustion, 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 deter-
mined 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 deter-
mine the proper orifice size.
A different pressure switch may be required at high altitude re-
gardless of the BTU/ft
3
content of the fuel used. Consult the
furnace Specification Sheet for pressure switch.
WARNING
P OSSIBLE PROPERTY DAMAGE , PERSONAL INJURY OR DEATH MAY
OCCUR IF THE CORRECT CONVERSION KITS ARE NOT INSTALLED . T HE
APPROPRIATE KITS MUST BE APPLIED TO ENSURE SAFE AND PROPER
FURNACE OPERATION . A LL CONVERSIONS MUST BE PERFORMED BY A
QUALIFIED INSTALLER OR SERVICE AGENCY .
PROPANE GAS CONVERSION
This unit is configured for natural gas, but may be converted
for use with L.P. gas. Refer to the section on PROPANE GAS/
HIGH ALTITUDE INSTALLATIONS for L.P. kit selection.
Consult the furnace Specification Sheet for a listing of appro-
priate kits. The indicated kits must be used to insure safe and
proper furnace operation. All conversions must be performed by
a qualified installer, or service agency.
CAUTION
T O 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 .
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 con-
vertible for use with propane gas by replacing the regulator spring
with a propane gas spring from an appropriate manufacturer’s
propane gas conversion kit. Taps for measuring the gas supply
pressure and manifold pressure are provided on the valve.
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” posi-
tion. Refer to the lighting instructions label or Startup Procedure
& Adjustment for use of this control during start up and shut
down periods.
GAS PIPING CONNECTIONS
The gas piping supplying the furnace must be properly sized based
on the gas flow required, specific gravity of the gas, 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.
Natural Gas Capacity of Pipe
In Cubic Feet of Gas Per Hour (CFH)
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
(Pressure 0.5 psig or less and pressure drop of 0.3" W.C.; Based on
0.60 Specific Gravity Gas)
CFH =
BTUH Furnace Input
Heating Value of Gas (BTU/Cubic Foot)
To connect the furnace to the building’s gas piping, the installer
must supply a ground joint union, drip leg, manual shutoff valve,
and line and fittings to connect to gas valve. In some cases, the
installer may also need to supply a transition piece from 1/2"
pipe to a larger pipe size.
The following stipulations apply when connecting gas piping. Re-
fer to Gas Piping Connections figure for typical gas line connec-
tions to the furnace.
• Gas piping must be supported external to the furnace
cabinet so that the weight of the gas line does not
distort the burner rack, manifold or gas valve.
• Use black iron or steel pipe and fittings for building piping.
Where possible, use new pipe that is properly chamfered,