RT-SVX069A-EN
19
Gas Heat Data
Table 3. Gas heater operating data
Heating Input Rate—Btu/h
125,000
180,000
225,000
250,000
Minimum Supply Gas Pressure Natural/LP
4.5/11.0
4.5/11.0
4.5/11.0
4.5/11.0
Manifold Gas Pressure
(a)
3.5
3.9
3.6
3.5
Combustion Blower Suction Pressure (1
st
Stage)
-1.3 to -1.7
-1.3 to -1.7
-1.1 to -1.5
-1.1 to -1.5
Combustion Blower Suction Pressure (2
nd
Stage)
-1.3 to -1.7
-1.3 to -1.7
-1.1 to -1.5
-1.1 to -1.5
Minimum Flame Sensing Current
(b)
5.0 Micro Amps DC
Normal Sensing Current Range
8.0 to 16 Micro Amps DC
Flue Gas Temperature Rise Above Ambient
230 to 300 F
Flue Gas Content - % CO
2
7.0% to 8.0%
Natural LP
7.5% to 9.0%
Minimum Supply Air Temperature Across Heat Exchanger
40° F
(a)
Staged gas heat units have a positive pressure gas valve. Never adjust the staged gas pressure valve to a negative pressure.
(b)
A voltage reading across pens (V+) and (V-) is equatable to the flame sensing current. One volt equals one micro amp.
Table 4. Piping
Length of Pipe (ft)
Iron Pipe Size (IPS) Inches
1/2" Pipe
3/4" Pipe
1" Pipe
1¼” Pipe
1½” Pipe
15
76
176
345
750
1220
30
52
120
241
535
850
45
43
99
199
435
700
60
38
86
173
380
610
75
77
155
345
545
Note:
Capacity of Pipe of Different Diameters and Lengths in Cu. Ft. Per Hr. with Pressure Drop of 0.3" and Specific Gravity of 0.60.
Table 5. Specific gravity multipliers
Specific Gravity
Multipliers
0.50
1.10
0.55
1.04
0.60
1.00
0.65
0.96
