Inlet gas supply pressures must be maintained within the ranges specified below. The supply pressure must be constant and avail- able with all other household gas fired appliances operating. The minimum gas supply pressure must be maintained to prevent unreliable ignition. The maximum must not be exceeded to pre- vent unit overfiring.
| Inlet Gas Supply Pressure |
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Natural Gas | Minimum:5.0" W.C. Maximum :10.0" W.C. |
Propane Gas | Minimum:11.0" W.C. Maximum :13.0" W.C. |
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 combus- tion 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 alti- tude and usage of either natural or propane gas. Contact your distributor for a tabular listing of appropriate altitude ranges and corresponding manufacturer’s high altitude (Natural, propane gas, and/or Pressure Switch) 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 pressure will prohibit the burner orifice from drawing the proper amount of air into the burner. This may cause incomplete combustion, flash- back, 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 artifi- cially derated, the appropriate orifice size must be determined based upon the BTU/ft3 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 determine the proper orifice size.
A different pressure switch may be required at high altitude regard- less of the BTU/ft3 content of the fuel used. Contact your distributor for a tabular listing of appropriate altitude ranges and correspond- ing manufacturer’s pressure switch kits.
PROPANE GAS CONVERSION
WARNING
POSSIBLE PROPERTY DAMAGE, PERSONAL INJURY OR DEATH MAY OCCUR IF THE CORRECT CONVERSION KITS ARE NOT INSTALLED. THE APPROPRIATE KITS MUST BE APPLIED TO INSURE SAFE AND PROPER FURNACE OPERATION. ALL CONVERSIONS MUST BE PERFORMED BY A QUALIFIED INSTALLER OR SERVICE AGENCY.
This unit is configured for natural gas. The appropriate manufacturer’s propane gas conversion kit, must be applied for propane gas installations. Refer to the Section VIII, Propane Gas / High Altitude Installations section for details.
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 convertible 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” position. Refer to the lighting instructions label or Section XIV, Startup Pro- cedure & Adjustment for use of this control during start up and shut
down periods.
GAS PIPING CONNECTIONS
GENERAL
CAUTION
TO AVOID POSSIBLE UNSATISFACTORY OPERATION OR EQUIPMENT DAMAGE DUE TO UNDERFIRING OF EQUIPMENT, USE THE PROPER SIZE OF NATURAL/PROPANE GAS PIPING NEEDED WHEN RUNNING PIPE FROM THE METER/TANK TO THE FURNACE.
When sizing a trunk line, be sure to include all appliances which will operate simultaneously when sizing a trunk line.
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 |
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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 |
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0.60 Specific Gravity Gas) |
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CFH = | BTUH Furnace Input |
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Heating Value of Gas (BTU/Cubic Foot) |
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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.
•Use black iron or steel pipe and fittings for building piping. Where possible, use new pipe that is properly chamfered, reamed, and free of burrs and chips. If old pipe is used, be sure it is clean and free of rust, scale, burrs, chips, and old pipe joint compound.
•Use pipe joint compound on male threads ONLY. Always use pipe joint compound (pipe dope) that is APPROVED FOR ALL GASSES. DO NOT apply compound to the first two threads.
•Use ground joint unions.
•Install a drip leg to trap dirt and moisture before it can enter the gas valve. The drip leg must be a minimum of three inches long.
•Install a 1/8" NPT pipe plug fitting, accessible for test gage connection, immediately upstream of the gas supply connection to the furnace.
•Always use a
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