5565591-YIM-B-1019
28 Johnson Controls Ducted Systems
Optional Gas Heat
These gas-fired heaters have aluminized-steel or optional
stainless steel, tubular heat exchangers with spark ignition.
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followed in all cases unless superseded by local codes or gas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.
Figure 23: Side Entry Gas Piping
Figure 24: Bottom Entry Gas Piping
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.
NOTE: There may be a local gas utility requirement specifying a
minimum diameter for gas piping. All units require a 3/4
inch pipe connection at the entrance fitting. Line should
not be sized smaller than the entrance fitting size.
Table 12: Gas Pipe Sizing - Capacity of Pipe
Length of
Pipe (ft.)
Nominal Iron Pipe Size
3/4 in. 1 in. 1-1/4 in.
10 278 520 1050
20 190 350 730
30 152 285 590
40 130 245 500
50 115 215 440
60 105 195 400
70 96 180 370
80 90 170 350
90 84 160 320
100 79 150 305
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