Installation
20
RT-SVX058B-EN
Gas Heat Data
Voltage Imbalance
Three phase electrical power to the unit must meet
stringent requirements for the unit to operate properly.
Measure each leg (phase-to-phase) of the power supply.
Each reading must fall within the utilization range stamped
on the unit nameplate. If any of the readings do not fall
within the proper tolerances, notify the power company to
correct this situation before operating the unit.
Excessive three phase voltage imbalance between phases
will cause motors to overheat and eventually fail.
The maximum allowable voltage imbalance is 2 percent.
Measure and record the voltage between phases 1, 2, and
3 and calculate the amount of imbalance as follows:
% Voltage Imbalance =
AV (Average Voltage) =
Table 3.
Gas heater operating data
Heating Input Rate—
Btu/h 115,000 100,000
72,000
Minimum Supply Gas
Pressure Natural/LP
4/11
4/11
4/11
Manifold Gas Pressure
(a)
(a) Staged gas heat units have a positive pressure gas valve. Never ad-
just the staged gas pressure valve to a negative pressure.
3.5
3.5
3.5
Combustion Blower Suction
Pressure (1
st
Stage)
-0.50 to -
0.55
-0.50 to -
0.55
-0.50 to -
0.55
Combustion Blower Suction
Pressure (2
nd
Stage)
-0.65 to -
0.70
-0.65 to -
0.70
---
Minimum Flame Sensing
Current
(b)
(b) A voltage reading across pens (V+) & (V-) is equatable to the flame
sensing current. One volt equals one micro amp.
5.0 Micro Amps DC
Normal Sensing Current
Range
8.0 to 16 Micro Amps DC
Flue Gas Temperature Rise
Above Ambient
250 to 350 F
Flue Gas Content - % CO
2
6.5 to 9.0 %
Natural LP
8.0 to 10.5%
Minimum Supply Air
Temperature Across Heat
Exchanger
40 F
Table 4.
Piping
Length of
Pipe (ft)
Iron Pipe Size (IPS) Inches
½” Pipe ¾” 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
Figure 17.
Schematic diagram for field gas piping to
units
Figure 18.
Typical unit gas train configuration
100 X AV - VD
where;
AV
Volt 1 + Volt 2 + Volt 3
3
