Integrated Gas Controller - Bryant Preferred Series Installation Instructions Manual

Integrated Gas Controller

The unit contains an Integrated Gas Controller (IGC) board.
The IGC control board uses a flue gas pressure switch that
senses pressure drop in the heat exchanger due to the combus-
tion inducer. See Fig. 42.
Fig. 42 — Flue Gas Pressure Switch and Pressure Sense
Tube (Typical Location)
When the thermostat calls for heating, power is sent to W on the
Integrated Gas Controller (IGC) board. An LED (light emitting di-
ode) on the IGC board turns on and remains on during normal op-
eration. A check is made to ensure that the burner thermal switch
SPADE
CONNECT
IGNITOR
STATUS LED
OVERCURRENT
FUSE PROTECTION
FLUE GAS
PRESSURE
SWITCH
FLUE GAS PRESSURE
SENSE TUBE
Fig. 43 — IGC Board Component Layout
26
and limit switch are closed, and that the pressure switch is open. If
the check was successful, the induced draft motor is energized.
When the pressure in the heat exchanger is low enough to close
the pressure switch, the ignition activation period begins. Once ig-
nition occurs, the IGC board will continue to monitor the condi-
tion of the burner thermal switch, the limit switches, the pressure
switch, and the flame sensor. Assuming the unit is controlled
through a room thermostat set for "fan auto," 30 seconds after ig-
nition occurs, the indoor fan motor will energize, and the outdoor
air dampers will open to their minimum position. If the "over tem-
perature limit" opens prior to the start of the indoor fan blower, the
IGC will shut down the burners, and the control will shorten the
30 second delay to 5 seconds less than the time to trip the limit.
For example, if the limit trips at 37 seconds, the control will
change the "fan on delay" from 45 seconds to 32 seconds. Once
the "fan on delay" has been modified, it will not change back to 30
seconds unless power is reset to the control.
When the thermostat is satisfied, W opens and the gas valve clos-
es, interrupting the flow of gas to the main burners. If the call for
W lasted less than 1 minute, the heating cycle will not terminate
until 1 minute after W became active. If the unit is controlled
through a room thermostat set for fan auto, the indoor fan motor
will continue to operate for an additional 45 seconds, then stop.
An LED indicator is provided on the IGC to monitor operation.
See Table 5 for a listing of the LED alarm codes.
See Fig. 43 for IGC board component layout. Fig. 44 is a typi-
cal IGC control wiring diagram.
See Fig. 45 for a flow chart detailing the operating sequence
for the IGC.
CAUTION
Do not detach the burner box from the heat exchanger panel. If
the burner box must be replaced, refer to the Service and
Maintenance Instructions for the unit.
REDUNDANT
GAS VALVE RELAY