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In making gas connections, avoid strains as they may cause noise and damage the con-
trols. A backup wrench is required to be used on the valve to avoid damage.
The capacities of gas pipe of different diameters and lengths in cu. ft. per hr. with pres-
sure drop of 0.3 in. and specific gravity of 0.60 (natural gas) are shown in Table 1.
After determining the pipe length, select the pipe size which will provide the minimum
cubic feet per hour required for the gas input rating of the furnace. By formula:
Gas Input of Furnace
(BTU/HR)
Cu. Ft. Per Hr. Required =
Heating Value of Gas
(BTU/FT
3
)
The gas input of the furnace is marked on the furnace rating plate. The heating value of
the gas (BTU/FT
3
) may be determined by consulting the local natural gas utility or the
L.P. gas supplier.
B. LP CONVERSION
Convert the valve to use liquefied petroleum (LP) gas by replacing the pressure regulator
spring with the conversion kit spring. This LP kit spring allows the regulator to maintain the
proper manifold pressure for LP gas. The correct burner LP orifices are included in the kit.
See Figure 14.
IMPORTANT: To remove the gas valve, remove the four screws securing the manifold pipe
to the burner tray. Remove the manifold pipe with gas valve attached. See Figure 15.
NOTE: Order the correct LP conversion kit from the furnace manufacturer. See Conversion
Kit Index shipped with unit for proper LP kit number. Furnace conversion to LP gas
must be performed by a qualified technician.
C. NOx MODELS
When converting units equipped with NOx inserts to LP gas, the stainless steel screen
mesh inserts in the entrance of the tubular exchangers are not required to meet SCAQMD
NOx emission levels. These inserts and 1/8؆ diameter retaining rod should be carefully
removed before firing this furnace on LP gas. IMPORTANT: This furnace is not designed to
operate on LP gas with the NOx inserts in place.
Step by step instructions on removing the NOx inserts and retaining rod are included in the
Conversion Kit Installation Instructions.
!
WARNING
FACTORY FOR USE ON NATURAL GAS ONLY. CONVERSION TO LP GAS
REQUIRES A SPECIAL KIT SUPPLIED BY THE DISTRIBUTOR OR MANUFAC-
TURER. MAILING ADDRESSES ARE LISTED ON THE FURNACE RATING PLATE,
PARTS LIST AND WARRANTY. FAILURE TO USE THE PROPER CONVERSION
KIT CAN CAUSE FIRE, CARBON MONOXIDE POISONING, EXPLOSION, PER-
SONAL INJURY, PROPERTY DAMAGE OR DEATH.
Maximum capacity of pipe in thousands of BTU per hour of undiluted liquefied petroleum
gases (at 11 inches water column inlet pressure).
(Based on a Pressure Drop of 0.5 Inch Water Column)
TABLE 2
LP GAS PIPE CAPACITY TABLE (CU. FT./HR.)
Nominal
Iron Pipe
Size, Inches
10 20 30 40 50 60 70 80 90 100 125 150
275 189 152 129 114 103 96 89 83 78 69 63
567 393 315 267 237 217 196 182 173 162 146 132
1,071 732 590 504 448 409 378 346 322 307 275 252
2,205 1,496 1,212 1,039 913 834 771 724 677 630 567 511
3,307 2,299 1,858 1,559 1,417 1,275 1,181 1,086 1,023 976 866 787
6,221 4,331 3,465 2,992 2,646 2,394 2,205 2,047 1,921 1,811 1,606 1,496
1/2
3/4
1
1-1/4
1-1/2
2
Length of Pipe, Feet
Example (LP): Input BTU requirement of unit, 150,000
Equivalent length of pipe, 60 ft. = 3/4؆ IPS required.