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
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