3. Insert field-supplied funnel into tube.
4. Pour 1 quart of water into funnel/tube. Water should run
through inducer housing, overfill condensate trap, and flow
into open field drain. (See Fig. 49.)
5. Remove funnel and tube from inducer housing and replace
drain connection cap and clamp.
Step 3—Purge Gas Lines
If not previously done, purge lines after all connections have been
made and check for leaks.
FIRE AND EXPLOSION HAZARD
Failure to follow this warning could result in a fire, explosion,
personal injury, or death.
Never purge a gas line into a combustion chamber. Never test
for gas leaks with an open flame. Use a commercially
available soap solution made specifically for the detection of
leaks to check all connections.
Step 4—Sequence of Operation
FURNACE MAY NOT OPERATE
Failure to follow this caution may result in furnace operation
stopping and water pipes freezing during cold weather.
Furnace control must be grounded for proper operation, or
control will lock out. Control is grounded through
green/yellow wire connected to gas valve and burner box
screw.
Using schematic diagram, follow sequence of operation through
different modes. (See Fig. 30.) Read and follow wiring diagram
carefully.
NOTE: If a power interruption occurs during a call for heat (W),
the control will start a 90-second blower-only ON period two
seconds after power is restored, if the thermostat is still calling for
gas heating. The Amber status code LED light will flash code 12
during the 90-second period, after which the LED will be ON
continuous, as long as no faults are detected. After the 90-second
period, the furnace will respond to the thermostat normally.
The blower door must be installed for power to be conducted
through the blower door interlock switch ILK to the furnace
control CPU, transformer TRAN, inducer motor IDM, blower
motor BLWM, hot-surface igniter HSI, and gas valve GV.
HEATING MODE
(See Fig. 27 for thermostat connections.)
The wall thermostat ″calls for heat,″ closing the R to W
circuit. The furnace control performs a self-check, verifies the
pressure switch contacts PRS are open, and starts the inducer
motor IDM.
a. Inducer Prepurge Period- As the inducer motor IDM
comes up to speed, the pressure switch contacts PRS close
to begin a 15-second prepurge period.
b. Igniter Warm-Up- At the end of the prepurge period, the
Hot-Surface igniter HSI is energized for a 17-second
igniter warm-up period.
c. Trial-for-Ignition Sequence- When the igniter warm-up
period is completed the main gas valve relay contacts
GVR-1 and -2 close to energize the gas valve GV, the gas
valve opens, and 24 vac power is supplied for a field-
installed humidifier at the HUM terminal. The gas valve
GV permits gas flow to the burners where it is ignited by
the Hot Surface Igniter HSI. Five seconds after the GVR-1
closes, a 2-second flame period begins. The HSI igniter
will remain energized until the flame is sensed or until the
2-second flame proving period begins.
Fig. 48—Inducer Housing Drain Tube Cap
A99118
Fig. 49—Filling Condensate Trap
A99119
37
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