Service Manual

INSTALLATION CONSIDERATIONS
30
GAS PIPING CONNECTIONS
CAUTION
T
O 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.
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.
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 =
Natural Gas Capacity of Pipe
In Cubic Feet of Gas Per Hour (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)
To connect the furnace to the building’s gas piping, the in-
staller 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 transi-
tion piece from 1/2" pipe to a larger pipe size.
The following stipulations apply when connecting gas piping.
Refer to the following figures for typical gas line connections
to the furnace.
1. Use black iron or steel pipe and fittings for the building
piping.
2. Use pipe joint compound on male threads only. Pipe
joint compound must be resistant to the action of the
fuel used.
3. Use ground joint unions.
4. 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.
5. Install a 1/8" NPT pipe plug fitting, accessible for test
gage connection, immediately upstream of the gas
supply connection to the furnace.
6. Use two pipe wrenches when making connection to
the gas valve to keep it from turning. The orientation
of the gas valve on the manifold must be maintained
as shipped from the factory.
7. Install a manual shutoff valve between the gas meter
and unit within six feet of the unit. If a union is in-
stalled, the union must be downstream of the manual
shutoff valve, between the shutoff valve and the fur-
nace.
8. Tighten all joints securely.