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Resize the common venting system to the minimum
vent pipe size determined by using the appropriate
tables in appendix G. (These are in the current stan-
dards of the National Fuel Gas Code ANSI Z223.1 in
the USA, and the appropriate Category 1 Natural Gas
and Propane appliances venting sizing tables in the
current standards of the CSA B149 Natural Gas and
Propane Installation Codes in Canada.)
Gas Piping
CAUTION
If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe
shall be installed at the gas valve and extend outside
the furnace cabinet.
Gas Supply
1 − This unit is shipped standard for left or right side instal-
lation of gas piping. Connect the gas supply to the pip-
ing assembly.
2 − When connecting the gas supply piping, consider fac-
tors such as length of run, number of fittings, and fur-
nace rating to avoid excessive pressure drop. Table 11
lists recommended pipe sizes for typical applications.
Nominal
Internal
Iron Pipe
Diameter
Size
inches
inches
(mm)
(3.048)
(mm)
3/8
.493
(9.53)
(12.522)
(2.69)
1/2
.622
175
(12.7)
(17.799)
(4.96)
3/4
.824
360
(19.05)
(20.930)
(10.19)
1
1.049
680
(25.4)
(26.645)
(919.25)
1−1/4
1.380
1400
(31.75)
(35.052)
(39.64)
1−1/2
1.610
2100
(38.1)
(40.894)
(59.46)
2
2.067
3950
(50.8)
(52.502)
(111.85)
2−1/2
2.469
6300
(63.5)
(67.713)
(178.39)
3
3.068
11000
(76.2)
(77.927)
(311.48)
NOTE − Capacity given in cubic feet (m
Gas Pipe Capacity − ft
10
20
30
(6.096)
(9.144)
95
65
52
(1.84)
(1.47)
120
97
(3.40)
(2.75)
250
200
(7.08)
(5.66)
465
375
(13.17)
(10.62)
950
770
(26.90)
(21.80)
460
1180
(41.34)
(33.41)
2750
2200
(77.87)
(62.30)
4350
3520
(123.17)
(99.67)
7700
6250
(218.03)
(176.98)
3
) of gas per hour and based on 0.60 specific gravity gas.
3 − The gas piping must not run in or through air ducts,
clothes chutes, gas vents or chimneys, dumb waiters,
or elevator shafts.
4 − The piping should be sloped 1/4 inch (6.4 mm) per 15
feet (4.57 m) upward toward the meter from the fur-
nace. The piping must be supported at proper intervals
[every 8 to 10 feet (2.44 to 3.01 m)] with suitable hang-
ers or straps. Install a drip leg inside vertical pipe runs
to the unit.
5 − In some localities, codes may require the installation of
a manual main shut-off valve and union (furnished by
the installer) external to the unit. The union must be of
the ground joint type.
Compounds used on threaded joints of gas piping
must be resistant to the actions of liquified petro-
leum gases.
NOTE − Install a 1/8 inch NPT plugged tap in the field piping
upstream of the gas supply connection to the unit. The tap
must be accessible for test gauge connection. See figure 13.
NOTE − If emergency shutoff is necessary, shut off the main
manual gas valve and disconnect the main power to the
furnace. The installer should properly label these devices.
TABLE 11
3
3
/hr (m
/hr)
Length of Pipe − feet (m)
40
50
60
(12.192)
(15.240)
(18.288)
45
40
36
(1.27)
(1.13)
(1.02)
82
73
66
(2.32)
(2.07)
(1.87)
170
151
138
(4.81)
(4.28)
(3.91)
320
285
260
(9.06)
(8.07)
(7.36)
660
580
530
(18.69)
(16.42)
(15.01)
990
900
810
(28.03)
(25.48)
(22.94)
1900
1680
1520
(53.80)
(47.57)
(43.04)
3000
2650
2400
(84.95
(75.04)
(67.96)
5300
4750
4300
(150.07)
(134.50)
(121.76)
Page 19
IMPORTANT
70
80
90
(21.336)
(24.384)
(27.432)
33
31
29
(.73)
(.88)
(.82)
61
57
53
(1.73)
(1.61)
(1.50)
125
118
110
(3.54)
(3.34)
(3.11)
240
220
205
(6.80)
(6.23)
(5.80)
490
460
430
(13.87)
(13.03)
(12.18)
750
690
650
(21.24)
(19.54)
(18.41)
1400
1300
1220
(39.64)
(36.81)
(34.55)
2250
2050
1950
(63.71)
(58.05)
(55.22)
3900
3700
3450
(110.43)
(104.77)
(97.69)
100
(30.480)
27
(.76)
50
(1.42)
103
(2.92)
195
(5.52)
400
(11.33)
620
(17.56)
1150
(32.56)
1850
(52.38)
3250
(92.03)
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