System Start-up
98
RT-SVX35H-EN
13. Press the STOP key at the Human Interface Module in
the unit control panel to stop the system operation.
Limited Modulating Gas Furnace
Limited 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 33% rated MBH up
to the nameplate rating of the unit. The turn down ratios,
therefore, is limited to 3:1.
Heat Exchanger
The heat exchanger drum, tubes and front and rear
headers utilities the same materials as the standard two
stage furnace.
Unit Control
The unit is controlled by a supply air temperature sensor
located in the supply air stream for VAV units. CV 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
-10V DC. The higher the voltage signal, the lower the call
for heat.
The 5 -10V DC. 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 pressure that is sensed by the
modulating gas valve. The greater the combustion air
pressure, the greater the call for gas and the higher the
firing rate of the heater. As the temperature setpoint is
reached, the Modulating Heat control will cause the
combustion air actuator to change the damper position to
a lower firing rate that matches the heat load of the space.
1. To verify and check system optimum combustion, use
to program the limited modulating heat
system components for 90% operation by scrolling
through the Human Interface displays.
2. Follow the checkout procedures discussed in the
previous steps.
Note:
The minimum firing rate for a limited modulating
gas furnace in step 8 is 33%. Travel of the
combustion air damper is limited by a welded stop.
3. Press the STOP key at the Human Interface Module in
the unit control panel to stop the system operation.
—
Modulating Gas Regulator Legend
1. Adjustment and indication of the air to gas ratio.
2. Adjustment and indication of the bias.
3. Connection for the Ambient compensation line.
4. Connection for the gas pressure sensing line.
5. Connection for the air pressure sensing line.
Note:
There are no serviceable parts on the SKP70
actuator. Should it become inoperative, replace the
actuator.
Figure 53. Modulating gas regulator
11
2
2
5
5
3
3
4
4
Summary of Contents for IntelliPak WEHE Series
Page 15: ...General Information RT SVX35H EN 15 Figure 1 Unit component layout and ship with locations...
Page 17: ...Installation RT SVX35H EN 17 Figure 2 Typical control module location...
Page 44: ...Installation 44 RT SVX35H EN Figure 27 Typical field power wiring for W_HE casings 2 through 6...
Page 56: ...Installation 56 RT SVX35H EN Figure 32 Wiring notes for CV controls...
Page 60: ...Installation 60 RT SVX35H EN Figure 35 Wiring notes VAV...
Page 68: ...System Start up 68 RT SVX35H EN Figure 38 Typical fenwall ignition control system...
Page 69: ...System Start up RT SVX35H EN 69 Figure 39 Typical Fenwall ignition control system...
