5188235-YIM-E-0518
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Johnson Controls Ducted Systems
Gas Piping
Proper sizing of gas piping depends on the cubic feet per hour
of gas flow required, specific gravity of the gas and the length of
run. “National Fuel Gas Code” Z223.1 (in U.S.A.) or the current
Gas Installation Codes CSA-B149.1 (in Canada) should be
followed in all cases unless superseded by local codes or gas
utility requirements. Refer to the Pipe Sizing Table 11. The
heating value of the gas may differ with locality. The value
should be checked with the local gas utility.
Figure 15: Side Entry Gas Piping
Figure 16: Bottom Entry Gas Piping
NOTE:
Maximum capacity of pipe in cubic feet of gas per hour
based upon a pressure drop of 0.3 inch W.C. and 0.6
specific gravity gas.
NOTE:
There may be a local gas utility requirement specifying a
minimum diameter for gas piping. All units require a 1/2
inch pipe connection at the entrance fitting. Line should
not be sized smaller than the entrance fitting size.
Gas Connection
The gas supply line can be routed within the space and roof
curb, exiting through the unit’s basepan. Refer to Figure 6 for
the gas piping inlet locations. Typical supply piping
arrangements are shown in Figures 15 and 16. All pipe nipples,
fittings, and the gas cock are field supplied or may be
purchased in Ducted Systems accessory kit #1GP0401.
Gas piping recommendations:
1.
A drip leg and a ground joint union must be installed in the
gas piping.
2.
Where required by local codes, a manual shut-off valve
must be installed outside of the unit.
3.
Use wrought iron or steel pipe for all gas lines. Pipe dope
should be applied sparingly to male threads only.
4.
All piping should be cleaned of dirt and scale by
hammering on the outside of the pipe and blowing out
loose particles. Before initial start-up, be sure that all gas
lines external to the unit have been purged of air.
5.
The gas supply should be a separate line and installed in
accordance with all safety codes as prescribed under
“Limitations”.
6.
A 1/8-inch NPT plugged tapping, accessible for test gage
connection, must be installed immediately upstream of the
gas supply connection to the unit.
7.
After the gas connections have been completed, open the
main shut-off valve admitting
normal gas pressure
to the
mains.
Check all joints for leaks with soap solution or other
material suitable for the purpose.
NEVER USE A FLAME.
Table 11: Gas Pipe Sizing - Capacity of Pipe
Length of
Pipe (ft.)
Nominal Iron Pipe Size
3/4 in.
1 in.
1-1/4 in.
10
278
520
1050
20
190
350
730
30
152
285
590
40
130
245
500
50
115
215
440
60
105
195
400
70
96
180
370
80
90
170
350
90
84
160
320
100
79
150
305
Natural gas may contain some propane. Propane is an
excellent solvent and will quickly dissolve white lead and
most standard commercial compounds. A special pipe
dope must be used when assembling wrought iron or
steel pipe. Shellac based compounds such as Gaskolac
or Stalastic, and compounds such as Rectorseal #5,
Clydes’s or John Crane may be used.
