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Figure 105. Air Damper location - two-stage and
modulating
Air
damper
Ultra Modulating Gas Furnace
Ultra modulating gas heaters are available for the 500, 850
and 1000 MBh heater sizes.
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
Symbio controller of the IntelliPak unit. The control signal
from the Symbio controller is 2-10V DC. The higher the
voltage signal, the higher the call for heat.
The 2 -10V DC signal the heat output of the gas heat
controller. The greater DC voltage, the greater the call for
gas and the higher the firing rate of the heater. As the
temperature setpoint is reached, the modulating heat
controller will cause the combustion air speed to change to
a lower firing rate that matches the heat load of the space.
For 2-stage heat, the control signal will have a mid range
voltage (4 - 5V DC) for stage one and 10V DC for stage
two.
Note: See figures in
"Ultra Modulating Burner Setup Two-
stage and Modulating Burner Setup," p. 123
850MBh representation.
Ultra Modulating Burner Setup Two-stage
and Modulating Burner Setup
Important: It is necessary to measure gas pressure at the
following points listed below. Install the
necessary fittings prior to starting the burner in
the Manual Override.
•
Inlet pressure (see
•
Main gas regulator outlet pressure (see
Figure 108, p.
•
Load line pressure (see
124)
•
Manifold pressure (see
RT-SVX072D-EN
for 500/
Figure 108, p.
125)
125)
Figure 107, p.
Figure 109, p.
125)
Important: Important: Flue readings should be taken from
center of the flue and at least 4 inches down
from the outlet. See
1. Program the following system components for
operation by scrolling through the user interface
displays:
a. Open the manual gas valve, located in the gas heat
section.
b. Set toggle switch located on heater control box to
ON.
c. Press Stop button on user interface.
d. Navigate to the Gas Heat Manual override screen.
See
Figure 106, p.
percentage to 1% and enable the 1st stage. Touch
the Auto button in the top right corner of the screen.
e. Turn the Supply Fan ON by the navigating to the
Manual Override Screen. Set the Fan speed to
100%.
Low Fire Adjustment
2. After the initial purge sequence and once the burner
has started, run the burner at low fire for ten minutes to
allow the burner to stabilize.
3. Use a flue analyzer to measure the oxygen (O
carbon dioxide (CO
), and carbon monoxide (CO)
2
levels in the flue gas. Take several readings to confirm
burner operation is stable.
If the measured O
level is between 17.0%-19.0% and
2
the CO
level is no more than 400ppm (corrected to 3%
2
O
), no adjustment is necessary. If an adjustment is
2
needed, turn the adjustment screw on the ratio
regulator. CCW to increase O2, CW to decrease O2.
See
Figure 107, p.
124.
Note: Ratio regulator turns affects amount of gas flow. The
number of turns on the ratio regulator is preset at the
factory. Only small adjustments should be made for
fine tuning combustion.
High Fire Adjustment
4. Adjust the user interface to operate the furnace at max
firing rate (100%) or 2
nd
operate for 10 minutes.
Note: The burner capacity is controlled by the
combustion fan speed. This has been preset at
the factory and normally does not need field
adjustment.
5. Check the inlet pressure at the tap upstream of the pilot
regulator. Refer to the illustration in
The inlet pressure should between 7.0" to 14.0" w.c.
6. Check the outlet pressure of the main gas regulator at
tap on the upstream solenoid valve. Refer to the
illustration in
Figure 108, p.
from the main gas regulator should be 6.0" w.c.
7. Check manifold pressure at tap closest to where the
valve train attaches to the burner. Refer to the
illustration in
Figure 109, p.
Unit Start-up
Figure 102, p.
122.
124. Set the modulating
),
2
Stage. Allow the system to
Figure 108, p.
125. The outlet pressure
125. Verify the manifold
125.
123
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