524581-YIM-I-0512
Johnson Controls Unitary Products
31
Optional Gas Heat
These 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 insure airflow falls within 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. "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followed in all cases unless superseded by local codes or gas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.
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. Line should
not be sized smaller than the entrance fitting size.
OPTIONAL
COIL
GUARD
SHOWN
Table 11: 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
