29
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 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 transition piece
from 1/2" pipe to a larger pipe size.
The following stipulations apply when connecting gas piping.
•
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 prop-
erly 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. Al-
ways use pipe joint compound (pipe dope) that is AP-
PROVED 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 mini-
mum 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.
•
Always use a back-up wrench when making the con-
nection 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; ex-
cessive 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 fur-
nace.
•
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 pen-
etration, rigid pipe must be used to reach the outside
of the cabinet. A semi-rigid connector to the gas pip-
ing 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 physi-
cal and thermal damage when installed. Ensure alu-
minum-alloy tubing and connectors are coated to pro-
tect against external corrosion when in contact with
masonry, plaster, or insulation, or subjected to re-
peated wetting by liquids such as water (except rain
water), detergents, or sewage.
E
DGES
OF
SHEET
METAL
HOLES
MAY
BE
SHARP
. U
SE
GLOVES
AS
A
PRECAUTION
WHEN
REMOVING
HOLE
PLUGS
.
WARNING
G
AS
P
IPING
C
HECKS
Before placing unit in operation, leak test the unit and gas con-
nections.
T
O
AVOID
THE
POSSIBILITY
OF
EXPLOSION
OR
FIRE
,
NEVER
USE
A
MATCH
OR
OPEN
FLAME
TO
TEST
FOR
LEAKS
.
WARNING
Check for leaks using an approved chloride-free soap and water
solution, an electronic combustible gas detector, or other ap-
proved testing methods.
NOTE:
Never exceed specified pressures for testing. Higher
pressure may damage the gas valve and cause subsequent
overfiring, resulting in heat exchanger failure.
Disconnect this unit and shutoff valve from the gas supply pip-
ing 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 shutoff valve before pressure testing sup-
ply piping system with test pressures equal to or less than 1/2
psig (3.48 kPA).
OPERATION
