5566020-JIM-C-1019
34
Johnson Controls Ducted Systems
Optional gas heat
The optional gas-fired heaters have aluminized-steel or optional
stainless steel, tubular heat exchangers with spark ignition.
Note:
On VAV units: individual VAV boxes must be fully open
in heating mode to ensure airflow falls within the
specified temperature rise range.
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.
Follow the “National Fuel Gas Code” Z223.1 (in U.S.A.) or the
current Gas Installation Codes CSA-B149.1 (in Canada) in all
cases unless they are superseded by local codes or gas utility
requirements.
Gas pipe sizing - capacity of pipe,
The heating value of the gas may vary by locality. You must
check the value with the local gas utility.
Figure 25: Side entry gas piping
Figure 26: 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. The line
must not be sized smaller than the entrance fitting size.
OPTIONAL
COIL
GUARD
SHOWN
Table 16: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
OPTIONAL
COIL
GUARD
SHOWN