Gas Pipe Sizing - Capacity Of Pipe; Side Entry Gas Piping; Bottom Entry Gas Piping - Johnson Controls ZE Series Installation Manual

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followed in all cases unless superseded by local codes or gas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 12. 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
Table 12: Gas Pipe Sizing - Capacity of Pipe
Length of
Pipe (ft.)
3/4 in.
10 278
20 190
30 152
40 130
50 115
60 105
70 96
80 90
90 84
100 79
Johnson Controls Ducted Systems
Nominal Iron Pipe Size
1 in. 1-1/4 in.
520 1050
350 730
285 590
245 500
215 440
195 400
180 370
170 350
160 320
150 305
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.
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.
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.
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