26
G
AS
P
IPING
C
ONNECTIONS
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.
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. Refer
to
Gas Piping Connections
figure for typical gas line connections to
the furnace.
• Gas piping must be supported external to the furnace cabinet
so that the weight of the gas line does not distort the burner
rack, manifold or gas valve.
•
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 gauge connection, immediately upstream of the gas supply connection
to the furnace.
•
Always use a back-up wrench when making the 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. Maximum torque for the gas valve connection is 375
in-lbs; excessive over-tightening may damage the gas valve.
•
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.
–
Semi-rigid metallic tubing and metallic fittings. Aluminum 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.
•
Use listed gas appliance connectors in accordance with their instructions. Connectors must be fully in the same room as the
furnace.
•
Protect connectors and semirigid tubing against physical and thermal damage when installed. Ensure aluminum-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.
T
O
AVOID
POSSIBLE
UNSATISFACTORY
OPERATION
OF
EQUIPMENT
DAMAGE
DUE
TO
UNDERFIRING
OR
EQUIPMENT
,
USE
THE
PROPER
SIZE
OF
NATURAL
/
PROPANE
GAS
PIPING
NEEDED
WHEN
RUNNING
PIPE
FROM
THE
METER
/
TANK
TO
THE
FURNACE
.
WARNING
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)
