349218-JIM-F-0512
Johnson Controls Unitary Products 27
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followed in all cases unless superseded by local codes or gas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 12. 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 13: External Supply Connection External Shut-Off
Figure 14: 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.
Table 11: Gas Application Data
Unit
Input
(MBH)
Output (MBH)
Temp Rise
(°F)
1
1. On VAV units, individual VAV boxes must be full open in
heating mode to insure airflow falls within temperature rise
range.
Size Opt.
J15ZJ
24 300 240 20-50
32 400 320 30-60
J18ZJ
24 300 240 20-50
32 400 320 30-60
J20ZJ
24 300 240 20-50
32 400 320 30-60
J25ZJ
24 300 240 20-50
32 400 320 30-60
Drip Leg
Main
Manual
Shut-off
Valve
Table 12: Gas Pipe Sizing - CapacIty of Pipe
Length of
Pipe (ft.)
Nominal Iron Pipe Size
1 in. 1-1/4 in.
10 520 1050
20 350 730
30 285 590
40 245 500
50 215 440
60 195 400
70 180 370
80 170 350
90 160 320
100 150 305
Table 13: Gas Heat Minimum Supply Air
Size
(Tons)
Heat Size
Supply Air (CFM)
Cooling Heating
Min Max Min Max
J15ZJ
(15)
24 4500 7000 4500 7000
32 4500 7000 4500 7000
J18ZJ
(17.5)
24 6000 8750 6000 8750
32 6000 8750 6000 8750
J20ZJ
(20)
24 6000 9400 6000 9400
32 6000 9400 6000 9400
J25ZJ
(25)
24 7500 12500 7500 12500
32 7500 12500 7500 12500
Drip Leg
Main
Manual
Shut-off
Valve
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