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Table 10: Gas Application Data
Unit
Input
Size
Opt.
(MBH)
24
-15
32
24
-18
32
24
-20
32
24
-25
32
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followed in all cases unless superseded by local codes or gas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.
NOTE: There may be a local gas utility requirement specifying
a minimum diameter for gas piping. All units require a
one-inch pipe connection at the entrance fitting.
Main
Manual
Shut-off
Valve
Figure 13: External Supply Connection External Shut-Off
Figure 14: Bottom Supply Connection External Shut-Off
22
Temp Rise
Output (MBH)
300
240
400
320
300
240
400
320
300
240
400
320
300
240
400
320
Drip Leg
Main
Manual
Shut-off
Valve
Drip Leg
Table 11: Gas Pipe Sizing - CapacIty of Pipe
Length of
Pipe (ft.)
(°F)
10
20-50
20
30-60
30
20-50
40
30-60
50
20-50
60
30-60
70
20-50
80
30-60
90
100
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.
Table 12: Gas Heat Minimum Supply Air
Size
(Tons)
-15
(15)
-18
(17.5)
-20
(20)
-25
(25)
Gas Connection
The gas supply line can be routed within the space and roof curb,
exiting through the unit's basepan. Refer to Figure 5 for the gas
piping inlet location. Typical supply piping arrangements are
shown in Figures 13 and 14. All pipe nipples, fittings, and the gas
cock are field supplied.
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.
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
Supply Air (CFM)
Heat Size
Cooling
Min
Max
24
4500
7000
32
4500
7000
24
6000
8750
32
6000
8750
24
6000
9400
32
6000
9400
24
7500
12500
32
7500
12500
Unitary Products Group
178113-BIM-D-0906
Heating
Min
Max
4500
7000
4500
7000
6000
8750
6000
8750
6000
9400
6000
9400
7500
12500
7500
12500
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