9
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 may be operated simultaneously.
The gas pipe supplying the furnace must be properly sized
based on gas flow required, specific gravity of the gas and
length of the run. The gas line installation must comply with
local codes, or in the absence of local codes, 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
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
0.60 Specific Gravity Gas)
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 Figure 3 for typical gas line connections to the
furnace.
•
Use black iron or steel pipe and fittings for the building
piping.
•
Use pipe joint compound on male threads only. Pipe
joint compound must be resistant to the action of the
fuel used.
•
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.
•
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.
•
Install a manual shutoff valve between the gas meter
and unit within six feet of the unit. If a union is installed,
the union must be downstream of the manual shutoff
valve, between the shutoff valve and the furnace.
•
Tighten all joints securely.
•
Connect the furnace to the building piping by one of the
following methods:
–
Rigid metallic pipe and fittings.
–
Semirigid metallic tubing and metallic fittings. Alumi-
num alloy tubing must not be used in exterior loca-
tions.
–
Listed gas appliance connectors, used in accordance
with the terms of their listing, must be completely in
the same room as the furnace.
–
Protect connectors and semirigid tubing against physi-
cal and thermal damage when installed. Ensure that
any aluminum-alloy tubing and connectors are coated
to protect against external corrosion when in contact
with masonry, plaster or insulation or are subject to
repeated wettings by such liquids as water (except
rain water), detergents or sewage.
``
Location of Manual Valve
(Installed Ahead of Ground
Joint Pipe Union)
Height Required
By Local Code
Ground Joint Pipe Union
To Be Installed Ahead Of
Gas Valve
Drip Leg
Reducing Coupling
1/2" x 1/8" with 1/8"
Pipe Plug To Measure
Line Gas Pressure
Figure 8
General Furnace Layout
Upflow Installations
When the gas piping enters through the right side of the
furnace
, the installer must supply the following fittings (start-
ing from the gas valve):
• 90 degree elbow.
• Close nipple.
• 90 degree elbow.
• Straight pipe to reach the exterior of the furnace
(Figures 9 & 10).
Figure 9
Gas Inlet Through Furnace Right Side
