5168276-XIM-B-0216
20 Johnson Controls Unitary Products
Optional Gas Heat
These gas-fired heaters have aluminized-steel or optional
stainless steel, tubular heat exchangers with spark ignition with
proven pilot.
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followed in all cases unless superseded by local codes or gas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 13. 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.
Figure 16: External Supply Connection External Shut-Off
Figure 17: Bottom Supply Connection External Shut-Off
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.
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 16 and 17. 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.
Table 11: Gas Application Data
Unit
Input
(MBH)
Output (MBH)
Temp Rise
(°F)
Size Opt.
180
N30 300 240 20-50
N40 400 320 30-60
240
N30 300 240 20-50
N40 400 320 30-60
Drip Leg
Main
Manual
Shut-off
Valve
Drip Leg
Main
Manual
Shut-off
Valve
Table 12: Gas Pipe Sizing - Capacity of Pipe
Length of
Pipe ft. (m)
Nominal Iron Pipe Size
1 in. 1-1/4 in.
10 (3)
520 (14.7) 1050 (29.7)
20 (6)
350 (9.9) 730 (20.6)
30 (9.1)
285 (8) 590 (16.7)
40 (12.1)
245 (6.9) 500 (14.1)
50 (15.2)
215 (6) 440 (12.4)
60 (18.2)
195 (5.5) 400 (12.4)
70 (21.3)
180 (5) 370 (10.4)
80 (24.3)
170 (4.8) 350 (9.9)
90 (27.4)
160 (4.5) 320 (9)
100 (30.4)
150 (4.2) 305 (8.6)
Table 13: Gas Heat Minimum Supply Air Imperial
Size
(Tons)
Heat Size
Supply Air (CFM)
Cooling Heating
Min Max Min Max
180
(15)
N30 4500 7000 4500 7000
N40 4500 7000 4500 7000
240
(20)
N30 6000 9400 6000 9400
N40 6000 9400 6000 9400
Table 14: Gas Heat Minimum Supply Air Metric
Size
(Tons)
Heat Size
Supply Air (M
3
/S)
Cooling Heating
Min Max Min Max
180
(15)
N30 2.13 3.3 2.13 3.3
N40 2.13 3.3 2.13 3.3
240
(20)
N30 2.83 4.44 2.83 4.44
N40 2.83 4.44 2.83 4.44
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