Goodman GMPN Installation & Operating Instructions Manual page 16

MAIN LIMIT SWITCH
The main limit switch is a 1/2" disc designed to shut off the burner gas should the outlet (bonnet)
temperature exceed the maximum design outlet air temperature. This switch is not adjustable. To
check the operation, block the return air flow through the unit temporarily. The limit switch should
function and shut the burner gas off within a few minutes. Remove the blockage and allow the
switch to cool sufficiently before reestablishing burner flames.
VENT PRESSURE SWITCH
This furnace utilizes a vent pressure switch which prevents the furnace from operating should any
portion of the vent system become restricted or a venter failure occur. To check this switch, place
the furnace in operation and remove the hose from the switch. The gas burners will extinguish.
Replacing the hose will allow the furnace to operate normally.
FLAME ROLL-OUT SWITCH
This furnace is equipped with four (4) flame roll-out switches. These manually resetable switches
are 1/2" disc type and are non-adjustable. They are designed to shut down the burner gas in the
event that flames are detected outside the heat exchanger. Should a switch function, contact a
qualified service person to determine the cause of function before resetting. To reset this
switch press the button on top of the switch after the furnace has cooled. To test the operation of
the switch with the furnace in operation, place an open flame on the disc portion of the switch.
The switch should function to shut down the burner gas. Wait until the furnace has cooled
sufficiently before resetting the switch.
FLAME SENSOR
The ignition is provided by electronic means. The burner flames should be extinguished if the
flame sensor fails to detect the presence of burner flame. To test, disconnect the flame sensor
wire before placing the furnace in operation. The electronic ignition should ignite the burners.
However the burners should shut off after a few seconds of operation. Disconnect the electrical
supply to the furnace, reinstall the disconnected sensor wire and reset the power supply to restore
the furnace to it's normal operation.
BLOWER DOOR INTERLOCK SWITCH
The purpose of the switch is to disconnect electrical power to the furnace should the blower door
become dislodged, removed, or not properly reinstalled such as performing a filter change.
ALLOWING THE FURNACE TO OPERATE WITHOUT THE BLOWER DOOR BEING
SECURELY IN PLACE CAN CAUSE COMBUSTION PRODUCTS TO BECOME CIRCULATED
THROUGHOUT THE LIVING AREA WHICH CAN CAUSE SERIOUS ILLNESS OR CARBON
MONOXIDE POISONING. To test the operation of this switch, place the furnace in operation and
remove the blower access door. The burner flames will extinguish and the venter and circulating
air blowers should both stop. To restore the unit to normal operation, shut off the electrical power
to the unit, replace the blower access door and restore the electrical power.
STACK OVER-TEMPERATURE SWITCH
Located on the venter blower housing, this switch is designed to shut down the burners should the
circulating air blower fail or the secondary coil become blocked. To test this switch, bypass the
main limit switch, disconnect the circulating air blower, and place the furnace in operation. After a
short period of time this switch should function shutting down the burners. IT IS VERY
IMPORTANT TO REMOVE THE BYPASS FROM THE MAIN LIMIT SWITCH AND REPLACE
THE WIRES WHICH WERE DISCONNECTED FOR THIS TEST PRIOR TO RETURNING THE
FURNACE IN NORMAL OPERATION.
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