JOHNSON CONTROLS
49
SECTION 2 – INSTALLATION
FORM 100.50-NOM6
ISSUE DATE: 8/07/2017
2
Even with these equipment design features, the acous-
tical characteristics of the entire installation must never
be overlooked. Additional steps for the acoustical char-
acteristics of a rooftop installation should be addressed
during the design phase of a project to avoid costly al-
terations after the installation of the equipment. Dur-
ing the design phase of a project, the designing en-
gineer should consider, at a minimum, the impact of
the equipment location, rooftop installation, building
structure, and duct work.
GAS HEATING
Gas Piping
Proper sizing of the 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 – latest Edition should be followed in all cases
unless superseded by local codes or gas company re-
.
TABLE 20 -
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 specific
gravity gas).
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 require-
ment specifying a minimum diameter for
gas piping. All units require a 1-1/2-inch
pipe connection at the entrance fitting.
Line size should not be sized smaller then
the entrance fitting 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 pip-
ing on the roof and enter the unit through the side of
the base rail. Typical supply piping arrangements are
FIGURE 19 -
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
LD11765A
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 propane.
Propane being an excellent solvent will
quickly dissolve white lead or most stan-
dard commercial compounds. Therefore,
a special pipe dope must be applied when
wrought iron or steel pipe is used. Shel-
lac 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
prescribed under “Limitations” listed in the be-
ginning 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 ma-
terial suitable for the purpose.
NEVER USE A
FLAME!
