ELECTRICAL CONTROLS
SUB•SYSTEM
Integrated Furnace Control (IFC)
Board
All units come with a solid state
integrated furnace control board to
monitor and control all furnace
operations. If an abnormal condition
occurs the IFC either stops the
furnace or takes other appropriate
safety action. It controls blower on
and off operation, and determines
what motor speed to run. Some
controls have provisions for constant
blower operation. All control and
main power wiring connects to the
IFC. Those used on (-)GRA/(·)GTA
units can control both an electronic
air cleaner and humidifier
accessories.
►
Current direct spark ignition IFC
boards now have an automative type
3 amp fuse to protect 24 volt circuit
components mounted on the board.
Over Temperature Switch(es)
The over temperature switch
prevents overheating conditions in
the burner compartment. The switch
mounts on the burners.
It is in the 24
volt control circuit. It must be
manually reset.
Pressure Switches
There are two pressure switches in
the 24 volt control circuit on upflow
units and only one on the downflow.
Each mounts near the induced draft
blower and condensate drain. One
checks for proper vent gas flow, the
other monitors the drain from the
secondary coil. While separate
switches, both act differentially
together.
FIGURE 10
INTEGRATED FURNACE CONTROL
FIGURE 11
OVER TEMPERATURE SWITCH
FIGURE 12
PRESSURE SWITCH
f
f
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