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GAS SUPPLY AND PIPING
The rating plate is stamped with the model number, type of
gas, and gas input rating. Make sure the furnace is equipped
to operate on the type of gas available.
Inlet Gas Supply Pressure
Natural Gas
Minimum: 5.0" W.C. Maximum :10.0" W.C.
Propane Gas
Minimum:11.0" W.C. Maximum :13.0" W.C.
Note: Inlet Gas Pressure Must Not Exceed the Maximum
Value Shown in Table Above.
The minimum supply pressure must not be varied downward
because this could lead to unreliable ignition. In addition,
gas input to the burners must not exceed the rated input
shown on the rating plate. Overfiring of the furnace could
result in premature heat exchanger failure. Finally, note that
inlet gas pressures in excess of 13 inches water column
could result in permanent damage to the gas valve.
HIGH ALTITUDE DERATE
If you are installing this furnace on natural gas and at an
altitude of 0 to 6000 feet for "C" and "D" model furnaces, or
0 to 7500 feet for "A" and "B" model furnaces, or 0 to 3000
feet for "S" and "V" model furnaces, no additional kits are
required. Please refer to the chart below for the proper natu-
ral gas manifold pressure required.
If you are installing this furnace on propane gas and at an
altitude of 0 to 6000 feet for "C" model furnace, 0 to 7000
feet for "S" and "V" model furnaces, or 0 to 7500 feet for "A"
and "B" model furnaces, the propane conversion kit, LPTK07,
LPTK07A or LPTK09, will be required. The "D" model fur-
nace at an altitude of 0 to 6000 feet, will require the propane
conversion kit, LPTK08 or LPTK09. Please refer to the charts
below for the proper propane gas manifold pressure required.
Model
Gas
Altitude
GUIA/B
Natural
0 - 7500 ft
GCIA/B
Propane
0 - 7500 ft
GUIC
Natural
0 - 6000 ft
GCIC
Propane
0 - 6000 ft
Natural
0 - 6000 ft
GUID
Propane
0 - 6000 ft
Model
Gas
Altitude
Natural
0 - 3000 ft
GUIS
Propane
0 - 7000 ft
GCIS
Propane
7001 - 8500 ft
Natural
0 - 3000 ft
GUIV
Propane
0 - 7000 ft
Propane
7001 - 8500 ft
At altitudes above 6000 feet for "C" and "D" model furnaces,
or 7500 feet for "A" and "B" model furnaces, or 7000 feet for
"S" and "V" model furnaces, a High Altitude Conversion Kit
is required. This is required regardless of the heat content of
the fuel used. For proper kit selection refer to the S-17 HIGH
ALTITUDE APPLICATION section in the SERVICING sec-
tion of this manual.
High altitude kits can be purchased depending upon the al-
titude.
38
Rev. 2
PRODUCT DESIGN
Manifold
Kit
Orifice
Pressure
None
#43
3.5" W.C.
LPTK07, 7A or 09
#55
10.0" W.C.
None
#43
3.5" W.C.
LPTK07, 7A or 09
#55
10.0" W.C.
None
#43
3.5" W.C.
LPTK08 or 09
#55
10.0" W.C.
Manifold Pressure
Kit
Orifice
High Stage Low Stage
None
#43
3.5" W.C.
1.9" W.C.
LPTK07, 7A or 09
#55
10.0" W.C.
6.0" W.C.
HALP09
#56
10.0" W.C.
6.0" W.C.
None
#43
3.5" W.C.
1.9" W.C.
LPTK07, 7A or 09
#55
10.0" W.C.
6.0" W.C.
HALP09
#56
10.0" W.C.
6.0" W.C.
CAUTION
The furnace will naturally derate itself with altitude.
Do not attempt to increase the firing rate by changing
orifices or increasing the manifold pressure. This can
cause poor combustion and equipment failure.
Adjustment of the manifold pressure to a lower pressure
reading than what is specified on the furnace nameplate is
not a proper derate procedure. With a lower density of air
and a lower manifold pressure at the burner orifice, the ori-
fice will not aspirate the proper amount of air into the burner.
This can cause incomplete combustion of the gas, flash
back, and possible yellow tipping.
CAUTION
To avoid possible unsatisfactory operation or equip-
ment damage due to underfiring of equipment, do not
undersize the natural gas piping from the meter to the
furnace. When sizing a trunk line per the tables, in-
clude all appliances on that line that could be oper-
ated simultaneously.
The gas pipe supplying the furnace must be properly sized
based on the cubic feet per hour of gas flow required, spe-
cific gravity of the gas and length of the run. The gas line
installation must comply with local codes, or in the absence
of local codes, with the latest edition of the National Fuel
Gas Code ANSI Z223.1.
NATURAL GAS CAPACITY OF PIPE IN CUBIC FEET OF
GAS PER HOUR (CFH)
Nominal Black Pipe Size
Length of
Pipe in Feet
1/2"
3/4"
10
132
278
20
92
190
30
73
152
40
63
130
50
56
115
60
50
105
70
46
80
43
90
40
100
38
(Pressure 0.5PSIG or less and Pressure Drop of 0.3" W.C. based on 0.60
Specific Gravity Gas)
BTUH FURNACE INPUT
CFH =
CALORIFIC VALUE OF GAS
1"
1-1/4"
1-1/2"
520
1050
350
730
285
590
245
500
215
440
195
400
96
180
370
90
170
350
84
160
320
79
150
305
1600
1100
980
760
670
610
560
530
490
460
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