Page 21
Gas Piping
Gas supply piping should not allow more than 0.5”W.C.
drop in pressure between gas meter and unit. Supply gas
pipe must not be smaller than unit gas connection
CAUTION
If a exible 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. The exible connector can then be added
between the black iron pipe and the gas supply line.
Gas Supply
WARNING
Do not over torque (800 in-lbs) or under torque (350 in-
lbs) when attaching the gas piping to the gas valve.
1 - This unit is shipped standard for left or right side
installation of gas piping (or top entry in horizontal
applications). Connect the gas supply piping into
the gas valve. The maximum torque is 800 in lbs
and minimum torque is 350 in lbs when attaching
the gas piping to the gas valve.
2 - When connecting the gas supply piping, consider
factors such as length of run, number of ttings, and
furnace rating to avoid excessive pressure drop.
Table 6 lists recommended pipe sizes for typical
applications.
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
furnace. The piping must be supported at proper
intervals [every 8 to 10 feet (2.44 to 3.01 m)] with
suitable hangers or straps. Install a drip leg in
vertical pipe runs to the unit.
5 - A 1/8” N.P.T. plugged tap or pressure post is located
on the gas valve to facilitate test gauge connection.
See gure 31.
6 - 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.
IMPORTANT
Compounds used on threaded joints of gas piping must
be resistant to the actions of liquied petroleum gases.
NOTE - If emergency shutoff is necessary, shut off the
main manual gas valve and disconnect main power to the
furnace. The installer should properly label these devices.
TABLE 6
Gas Pipe Capacity - ft3/hr (m3/hr)
Nominal
Iron Pipe
Size Inches
(mm)
Internal
Diameter
inches
(mm)
Length of Pipe - feet (m)
10
(3.048)
20
(6.096)
30
(9,144)
40
(12,192)
50
(15.240)
60
(18.288)
70
(21.336)
80
(24.384)
90
(27.432)
100
(30,480)
1/2
(12.7)
.622
(17.799)
172
(4.87)
118
(3.34)
95
(2.69)
81
(2.29)
72
(2.03)
65
(1.84)
60
(1.69)
56
(1.58)
52
(1.47)
50
(1.42)
3/4
(19.05)
.824
(20.930)
360
(10.19)
247
(7.000)
199
(5.63)
170
(4.81)
151
(4.23)
137
(3.87)
126
(3.56)
117
(3.31)
110
(3.11)
104
(2.94)
1
(25.4)
1.049
(26.645)
678
(19.19)
466
(13.19)
374
(10.59)
320
(9.06)
284
(8.04)
257
(7.27)
237
(6.71)
220
(6.23)
207
(5.86)
195
(5.52)
1-1/4
(31.75)
1.380
(35.052)
1350
(38.22)
957
(27.09)
768
(22.25)
657
(18.60)
583
(16.50)
528
(14.95)
486
(13.76)
452
(12.79)
424
(12.00)
400
(11.33)
1-1/2
(38.1)
1.610
(40.894)
2090
(59.18)
1430
(40.49)
1150
(32.56)
985
(27.89)
873
(24.72)
791
(22.39)
728
(20.61)
677
(19.17)
635
(17.98)
600
(17.00)
2
(50.8)
2.067
(52.502)
4020
(113.83)
2760
(78.15)
2220
(62.86)
1900
(53.80)
1680
(47.57)
1520
(43.04)
1400
(39.64)
1300
(36.81)
1220
(34.55)
1160
(32.844)
2-1/2
(63.5)
2.469
(67.713)
6400
(181.22)
4400
(124.59)
3530
(99.95)
3020
(85.51)
2680
(75.88)
2480
(70.22)
2230
(63.14)
2080
(58.89)
1950
(55.22)
1840
(52.10)
3
(76.2)
3.068
(77.927)
11300
(319.98)
7780
(220.30)
6250
(176.98)
5350
(151.49)
4740
(134.22)
4290
(121.47)
3950
(111.85)
3670
(103.92)
3450
(97.69)
3260
(92.31)
NOTE - Capacity given in cubic feet (m3 ) of gas per hour and based on 0.60 specic gravity gas.
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