SYSTEM OPERATION
7
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Inlet gas supply pressures must be maintained within the
ranges specied below. The supply pressure must be constant
and available with all other household gas red appliances
operating. The minimum gas supply pressure must be
maintained to prevent unreliable ignition. The maximum must
not be exceeded to prevent unit overring.
Natural Gas Minimum: 4.5" w.c. Maximum: 10.0" w.c.
Propane Gas Minimum: 11.0" w.c. Maximum: 13.0" w.c.
This unit is equipped with a 24 volt gas valve controlled during
furnace operation by the integrated control module. 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 section of this
manual or the installation instructions for use of this control
during start up and shut down periods.
To avoid possible unsatisfactory operation or
equipment damage due to underfiring of equipment,
use the proper size of natural gas piping needed when
running pipe from the meter to the furnace.
The gas piping supplying the furnace must be properly
sized based on the gas ow required, specic 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.
Length of Nominal Black Pipe Size
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
CFH =
(Pressure 0.5 psig or less and pressure drop of 0.3" W.C.; Based on 0.60 Specific
Gravity Gas)
BTUH Furnace Input
Heating Value of Gas (BTU/Cubic Foot)
Before placing unit in operation or upon completion of
servicing, leak test the unit and gas connections.
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Check for leaks using an approved chloride-free soap and
water solution, an electronic combustible gas detector, or
other approved testing methods.
Never exceed specied pressures for testing. Higher
pressure may damage the gas valve and cause subsequent
overring, resulting in heat exchanger failure. Disconnect
this unit and shuto valve from the gas supply piping system
before pressure testing the supply piping system with
pressures in excess of 1/2 psig (3.48 kPa). Isolate this unit
from the gas supply piping system by closing its external
manual gas shuto valve before pressure testing supply
piping system with test pressures equal to or less than 1/2
psig (3.48 kPa).
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