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:
Cu. Ft. Per Hr. Required =
Gas Input of Furnace (BTU/HR)
Heating Value of Gas (BTU/FT3)
The gas input of the furnace is marked on the furnace rating plate. The heating value of the gas (BTU/FT3) may be determined by consulting the local natural gas utility or the L.P. gas supplier.
B. LP CONVERSION
!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.
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.
TABLE 2
LP GAS PIPE CAPACITY TABLE (CU. FT./HR.)
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)
Nominal |
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| Length of Pipe, Feet |
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Iron Pipe |
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10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 | 125 | 150 | ||
Size, Inches | |||||||||||||
1/2 | 275 | 189 | 152 | 129 | 114 | 103 | 96 | 89 | 83 | 78 | 69 | 63 | |
3/4 | 567 | 393 | 315 | 267 | 237 | 217 | 196 | 182 | 173 | 162 | 146 | 132 | |
1 | 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 | ||
2 | 6,221 | 4,331 | 3,465 | 2,992 | 2,646 | 2,394 | 2,205 | 2,047 | 1,921 | 1,811 | 1,606 | 1,496 | |
Example (LP): Input BTU requirement of unit, 150,000
Equivalent length of pipe, 60 ft. = 3/4″ IPS required.
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