Trane ACONT900AC43UA - Three Stage Furnace Gas Pressure Measurement & Adjustment; Setting Manifold Pressure Using Contingency Mode

GF - D 11
Gas Valves
Step 14
If the firing rate cannot be obtained with the manifold
pressures specified in Table 4, check inlet gas piping
for proper sizing and pressure. If insufficient, correct
and/or contact gas company to adjust input pressure.
Step 15
When the correct operating manifold pressures are
obtained, turn the furnace OFF. Remove the field
supplied manometer tubing, 1/8" NPT barbed fitting,
and the tee installed at the beginning steps. TIGHTEN
DOWN THE MANIFOLD ADJUSTMENT COVERS
AND REINSTALL THE MANIFOLD PRESSURE
MEASUREMENT FITTING. Using a leak detection
solution or soap suds, check for leaks at plug or outlet
pressure tap screw.
Step 16
Reconnect the thermostat data line to the D terminal
of the furnace (Figure 27).
Figure 27
Step 17
Turn on the 115V power to the furnace. With the
thermostat data line connected to the furnace and
communications between the thermostat and the
furnace reestablished, the furnace operation will now
be controlled by the communicating comfort control.
NOTE: Gas valave set-up on the user interface unit is
not addressed. This was implemented on Modulating
furnaces April 2010.
Setting Manifold Pressure
Using Contingency Mode
Three Stage Furnace Gas Pressure
Measurement & Adjustment
Option 1 - Step 1
Remove power from the furnace and disconnect the
comfort control data wire labeled “D”.
Step 2
Re-apply 115 VAC to the furnace. The user Interface
will display WAIT, then model and serial number.
Step 3
Set up the furnace in the contingency mode of
operation at the User Interface for the first stage of
heat with a 50% duty cycle.
Step 4
Remove 115 VAC power from the furnace. Do not
repower the furnace until the Green LED (Figure 28)
on the inducer motor drive board goes out.
Figure 28
Step 5
Apply 115 VAC power to the furnace. The furnace User
Interface will display WAIT, and then the display will
change to CONTINGENCY MODE STG 1 50%.
(Figure 29) Let the furnace go through the first stage
learning routine and its temperature rise stabilize. The
temperature rise and learning routine will take less
than three minutes.
See pressure test connection diagrams for hook-up
configuration (Figures 46 & 47)