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21
Figure 22. Typical Gas Piping
Table 7. Capacity of Black Iron Gas Pipe
(cu. ft. per hour) for Natural Gas
(specific gravity = .60)
To Gas
Supply
Floor
Inducer
Alt. Gas
Line Entry
Floor Cavity
Gas
Valve
Burner
Box
Control
Board
Main
Blower
NOMINAL LENGTH OF PIPE RUN
BLACK IRON (feet)
PIPE DIAMETER
(in.) 1020304050607080
1/2 130 90 75 65 55 50 45 40
3/4 280 190 150 130 115 105 95 90
1 520 350 285 245 215 195 180 170
1 1/4 1050 730 590 500 440 400 370 350
1 1/2 1600 1100 890 760 670 610 560 530
CAPACITY OF BLACK IRON GAS PIPE (CU. FT. PER HOUR)
FOR NATURAL GAS (SPECIFIC GRAVITY - 0.60)
The cubic feet per hour listed in the table above must be greater than
the cubic feet per hour of gas flow required by the furnace.
To determine the cubic feet per hour of gas flow required by the furnace,
divide the input rate of the furnace by the heating value of the gas:
Cubic Feet Input To Furnace (Btu/hr)
Per Hour Required Heating Value of Gas (Btu/Cu. Ft.)
=
If the test pressure is less than or equal to 1/2
psig (14 in. water column), the furnace must be
isolated from the gas supply line by closing the
manual shut-off valve.
Leak Check
After the gas piping to the furnace is complete,
all connections must be tested for gas leaks. To
check for leaks use only a soap and water solu-
tion or other approved method.
High Altitude Derate
The nameplate input rating for the furnaces
apply for elevations up to 4,000 feet above sea
level for US and Canada. If the elevation for the
furnace location is higher than 4,000 feet above
sea level, the furnace input must be derated by
using the appropriate orifice size listed in
Table 8.
NOTE: The density of air decreases with in-
creasing elevation above sea level. This re-
duces the quantity of combustion air drawn into
the furnace under normal operation and requires
the unit be derated by using smaller gas orifices
or lower manifold pressure.
CONVERSION
This furnace can be converted from the fac-
tory-equipped gas to either natural gas (for LP
gas ready models), or LP gas (for natural gas
ready models). Conversions must be made by
qualified service personnel, using only factory
authorized or approved parts. The required
conversion orifices are supplied with the fur-
nace.
!
WARNING:
DO NOT REMOVE OR DEFACE THE
ORIGINAL RATING PLATE.
!
CAUTION:
The gas supply shall be shut off prior to
disconnecting the electrical power,
before proceeding with the conversion.
To Turn Off Fuel Supply to the Appliance:
1. Set the room thermostat to “OFF” or its
lowest temperature setting.
2. Turn OFF the main gas supply to the appli-
ance at the manual valve, outside of the
appliance casing.
3. Remove the control access panel / lou-
vered door.
4. Move the appliance gas valve lever/knob to
the “OFF” position.
5. Turn OFF the electrical power to the appli-
ance.