RT-SVX36G-EN
159
Unit Start Up
Full Modulating Gas Furnace
Full Modulating gas heaters are available for the 500, 850 and 1000 MBH heater sizes. These heaters
are available in the same cabinet sizes as the current heaters.
The firing rate of the unit can vary from the pilot rate of 125 MBH up to the nameplate rating of the
unit. The turn down ratios, therefore, vary from 4:1 for the 500 MBH to 8:1 for the 1000 MBH heater.
Heat Exchanger
The heat exchanger drum, tubes and front and rear headers are constructed from stainless steel
alloys.
Unit control
The unit is controlled by a supply air temperature sensor located in the supply air stream for
Discharge Temperature Control units. Zone Temperature Control units have two sensors, one
located in the supply air stream and the zone sensor. The temperature sensor signal is sent to the
Heat module of the IntelliPak Unit Control. The control signal from the Heat Module is an inverse
proportional 5 -10 VDC. The higher the voltage signal, the lower the call for heat.
The 5 -10 VDC. signal controls the angular position of the combustion air damper through a direct
coupled damper actuator motor. The position of the air damper in turn controls the combustion air
Figure 84. Natural gas combustion curve (ratio of oxygen to carbon dioxide in percent)
Figure 85. Gas valve adjustment screw locations
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
0 1 2 3 4 5
6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Percent Oxygen
Percent Carbon Dioxide
Curve Fuel
A = 1,000 BTU per cu. ft.
of Natural Gas.
A
