102777-YIM-E-0206
16 Unitary Products Group
GAS HEATING
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-Latest Edition
should be followed in all cases unless superseded by local
codes or gas company requirements. Refer to Table 10.
The heating value of the gas may differ with locality. The
value should be checked with the local gas utility.
NOTE: There may be a local gas utility requirement specify-
ing a minimum diameter for gas piping. All units
require a 1-1/4 inch pipe connection at the entrance
fitting. Line should not be sized smaller than 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.
Refer to Fig. 13 -- 16 to locate the access opening. Typical
supply piping arrangements are shown in Figure 5.
Gas piping recommendations:
1. A drip leg and a ground joint union must be installed 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.
4. All piping should be cleaned of dirt and scale by ham-
mering on the outside of the pipe and blowing 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 installed in
accordance with all safety codes as prescribed under
Limitations. After the gas connections have been com-
pleted, open the main shutoff valve admitting normal gas
pressure to the mains. Check all joints for leaks with
On VAV units with gas fired furnace, ALL INDIVID-
UAL ROOM DAMPER BOXES MUST BE CON-
TROLLED FULL OPEN DURING HEATING
OPERATION TO ENSURE PROPER AIRFLOW
OVER THE FURNACE. A control contact between
D1 and D2 on TB3 is provided for the damper box
interlock. This contact is normally open, thus is
closed during heating operation.
TABLE 10: PIPE SIZES
LENGTH IN
FEET
NOMINAL IRON PIPE, SIZE
1-1/4 IN.
1
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.
1-1/2 IN.
1
2 IN.
1
10 1,050 1,600 3,050
20 730 1,100 2,100
30 590 890 1,650
40 - 760 1,450
50 - - 1,270
60 - - 1,150
70 - - 1,050
80 - - 990
FIGURE 6 - TYPICAL GAS PIPING CONNECTION
Natural gas may contain some propane. Propane,
being an excellent solvent, will quickly dissolve
white lead or most standard commercial com-
pounds. Therefore, a special pipe dope must be
applied when wrought iron or steel pipe is used.
Shellac base compounds such as Gaskolac or
Stalastic, and compounds such as Rectorseal #5,
Clyde's or John Crane may be used.
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