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2
JOHNSON CONTROLS
FORM 100.50-NOM6 (1207)
GAS PIPING
Proper sizing of the gas piping depends on the cubic feet
per hour of gas fl ow required, specifi c gravity of the gas
and the length of run. National Fuel Gas Code Z223.1
– latest Edition should be followed in all cases unless
superseded by local codes or gas company requirements.
Refer to Table 2-19.
The heating value of the gas may differ with locality.
The value should be checked with the local gas utility.
There may be a local gas utility re-
quirement specifying a minimum
diameter for gas piping. All units re-
quire a 1-1/2-inch pipe connection at
the entrance fi tting. Line size should
not be sized smaller then the entrance
fi tting size.
GAS CONNECTION
The gas supply line should be routed within the space
and penetrate the roof at the gas inlet connection of
the unit. The gas piping can enter the unit through an
opening in the base of the gas heat section. Many local
codes require that a shut off valve be located external to
the unit. In these cases it is easier to run the gas piping
on the roof and enter the unit through the side of the
base rail. Typical supply piping arrangements are shown
in Figure 2-13.
GAS HEATING
TABLE 2-19 – PIPE SIZES
LENGTH IN
FEET
NOMINAL IRON PIPE SIZE
1-1/2 IN.
1
2 IN.
1
10 1,600 3,050
20 1,100 2,100
30 890 1,650
40 760 1,450
50 1,270
60 1,150
70 1,050
80 990
1
Maximum capacity of pipe in cubic feet of gas per
hour (based upon a pressure drop of 0.3 inch water
column and 0.6 specifi c gravity gas).
FIG. 2-13 – TYPICAL GAS PIPING CONNECTION
1-1/2" FPT
FACTORY
PIPING
ROOF
CURB
DRIP LEG
UNIT BASERAIL
UNION (For Servicing)
1/8" NPT PLUG
MANUAL GAS
VALVE
PITCH POCKET
ROOF
Gas Piping Recommendations
1. A drip leg and a ground joint union must be in-
stalled in the gas piping.
2. When required by local codes, a manual shut-off
valve will have to 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 pro-
pane. Propane being an excellent
solvent will quickly dissolve white
lead or most standard commercial
compounds. Therefore, a special pipe
dope must be applied when wrought
iron or steel pipe is used. Shellac
base components such as Gaskolac
or Stalastic, and compounds such as
Rectorseal #5, Clyde’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 blow-
ing out the loose particles. Before initial start-up,
be sure that all of the gas lines external to the unit
have been purged of air.
5. The gas supply should be a separate line and in-
stalled in accordance with all safety codes as pre-
scribed under “Limitations” listed in the beginning
of this section. After the gas connections have been
completed, open the main shutoff valve admitting
gas pressure to the mains. Check all joints for
leaks with soap solution or other material suitable
for the purpose. NEVER USE A FLAME!
LD11765A