Sequence Of Operation; Heating Mode - Bryant 350AAV Installation, Start-Up, And Operating Instructions Manual

Fig. 46—Inducer Housing Drain Tube Cap
Fig. 47—Filling Condensate Trap
WARNING: 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.
IV. SEQUENCE OF OPERATION
CAUTION: 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. 35.) 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
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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.
A. Heating Mode
(See Fig. 31 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
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.
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Sequence- When the igniter