PRODUCT DESIGN
57
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.
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)
Natural Gas Capacity of Pipe
In Cubic Feet of Gas Per Hour (CFH)
BTUH Furnace Input
Heating Value of Gas (BTU/Cubic Foot)
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 pip-
ing. Refer to the following figures for typical gas line con-
nections to the furnace.
1. Use black iron or steel pipe and fittings for the build-
ing 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.
9. Connect the furnace to the building piping by one of
the following methods:
– Rigid metallic pipe and fittings.
– Semi-rigid metallic tubing and metallic fittings. Alu
minum alloy tubing must not be used in exterior
locations. In order to seal the grommet cabinet
penetration, rigid pipe must be used to reach the
outside of the cabinet. A semi-rigid connector to
the gas piping may be used from there.
10. Use listed gas appliance connectors in accordance with
their instructions. Connectors must be fully in the same
room as the furnace.
11. Protect connectors and semi-rigid tubing against physi-
cal and thermal damage when installed. Ensure alumi-
num-alloy tubing and connectors are coated to protect
against external corrosion when in contact with masonry,
plaster, or insulation, or subjected to repeated wetting
by liquids such as water (except rain water), detergents,
or sewage.
CAUTION
E
DGES OF SHEET METAL HOLES MAY BE SHARP.
U
SE GLOVES A PRECAUTION
WHEN REMOVING HOLE PLUGS.
DIRECT/STANDARD INLET PIPING
When gas piping enters directly to the gas valve through the
standard inlet hole (upflow through the right side panel), the
installer must supply straight pipe with a ground joint union
to reach the exterior of the furnace. NOTE: The rigid pipe
must be long enough to reach the outside of the cabinet to
seal the grommet cabinet penetration on 90% furnaces. A
semi-rigid connector to the gas piping can be used outside
the cabinet per local codes.
INDIRECT/ALTERNATE INLET PIPING
When gas piping enters indirectly to the gas valve through
the alternate gas inlet hole the installer must supply the
following fittings (starting from the gas valve) to reach the
outside of the cabinet (NOTE: On the 90% furnaces the in-
staller must swap the alternate inlet hole plug with the stan-
dard inlet grommet in order to seal the cabinet):
• Coupling.
• 90 degree elbow.
• 2 inch close nipple.
• 90 degree elbow.
• Straight pipe, with a ground joint union, to reach the
exterior of the furnace. NOTE: The rigid pipe must be
long enough to reach the outside of the cabinet so as
to seal the grommet cabinet penetration on the 90%
furnaces. A semi-rigid connector to the gas piping can
be used outside the cabinet per local codes.
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