46 18-CD30D1-12
Installer’s Guide
B) GAS VALVE SETUP (MANIFOLD PRESSURE
ADJUSTMENT)
NOTE: To obtain an accurate manifold pressure mea-
surement ,the manifold pressure must be referenced
to the burner box, since the burner box pressure tap
equalizes the gas valve pressure regulator. To do so,
install a tee and section of tube (field supplied) in the
tubing between the tee coming from the burner box
tube and the gas valve manifold pressure measure-
ment fitting. This tube and tee is in addition to the
tube attached to the gas valve pressure tap on the
outlet side of the gas valve. See Figure 58.
NOTE: In order to properly set the manifold gas
pressure, the incoming line gas pressure should be
tested with the unit off and again with the unit operat-
ing at the high heat setting to ensure adequate fuel
supply to the furnace. The incoming gas pressure
should be 5" W.C. minimum and 13.8" W.C. maximum
for natural gas.
1) Before Setting Manifold Gas Pressure
Setting the manifold gas pressures is critical for the cor-
rect operation of this furnace.
Before entering the Gas Valve Setup mode:
a. Turn comfort control system switch to the OFF position
and fan switch to the AUTO position.
b. Prime the furnace condensate trap.
Any call for heat or fan by the comfort control will abort
or cancel the Gas Valve Setup mode. The unit will
stay in Gas Valve Setup mode for a maximum of 20
minutes.
c. Connect dual port manometer & field tubing per Figure
58 on page 47.
Note: MIN = 40% (low) heat, MAX = 100% (high) heat
Setting Manifold Gas Pressure
2) Setting “MIN” manifold gas pressure
To enter the Gas Valve Setup mode:
a. Scroll down on the user interface to Unit Test.
b. Scroll to the right and select “Gas Val Setup”.
c. Push the Enter button.
d. Select “MIN” and push the Enter button.
e. When asked “Are You Sure”, select Yes, and push the
Enter button.
f. The furnace will now begin the ignition sequence.
g. If pressure switch 1 & 2 learning routines have not
been performed; after successful ignition, the inducer
will go through this operation. (see Inducer Learning
Routine section).
UNIT TEST MODE
A) SIMPLE
Note:
Stage 1 = 40% (low) heat, Stage 2 = 100% (high) heat
A qualified technician can cycle the Variable Speed
Indoor Blower and the Modulating Gas Furnace
through its operation at the User Interface.
• The unit test cycle is entered at the user interface.
• The test cycle can only be entered when the comfort
control has no demand and the furnace IFC is not
reporting a fault. Turn the comfort control to the Off
position and turn the fan control to Auto. This will
ensure the unit test cycle will not be interrupted.
• Scroll down using the button at the user interface until
the display reads:
• UNIT TEST. Press the Enter button.
• UNIT TEST and NO (NO) will now be displayed. Use
the or arrow button to change the NO to a YES and
then press ENTER.
• ARE YOU SURE and NO (NO) will now be displayed. Use
the or arrow button to change the NO to a YES and
then press ENTER.
• UNIT TEST and Y1 ON FAN ON will now be displayed.
The variable speed indoor blower will then be turned
on by the IFC for 10 seconds and then off.
• Furnace will then transition to the ignition sequence.
STAGE OFF will now be displayed. After a 45 second
heat fan on delay, Stage 1 will be displayed and 40%
(low) heat inducer speed will be energized for 10
seconds.
• Stage 2 will be displayed and 100% (high) heat inducer
speed will be energized for 10 seconds.
• The control transitions to off.
• The Model and Serial Number will be displayed.
• The variable speed indoor blower will now operate for the
heat exchanger cool down cycle and then shut off at the
end of the cycle.
• The comfort control can now be returned to the
homeowner’s desired settings.
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