Install Instructions

40
TROUBLESHOOTING
If the furnace fails to operate check the following:
• Is the thermostat operating properly?
• Are the blower compartment door(s) in place?
• Is the furnace disconnect closed?
• Has the circuit breaker tripped or the control board fuse
burned open?
• Is the gas turned on?
• Are any manual reset switches open?
• Is the filter dirty or plugged?
• Is the flame sensor coated? (Remove and clean with
steel wool. (Do not use emery cloth or sandpaper!)
• Is there blockage in the condensate drain switch? Also
verify that there is no double trapping of condensate.
• Is the secondary heat exchanger free of debris and
clogs?
• Is evaporator coil clean and free of debris (If applicable).
• Are all the LED’s on the furnace control board constantly
ON? If not, refer to
Table 13 or the wiring diagram, Figure
31 (page 30)
or Figure 32 (page 31) to determine fault
condition.
• Are all the LED’s on the motor control board constantly
ON? If not, refer to
Table 14 to determine fault condition.
IMPORTANT NOTE:
The furnace will lock out after 5 failed attempts for ignition
and will try again every hour if the call for heat remains.
• If the Inducer Blower is operating, and items above have
been verified, check the Blower Limit Switch and reset if
necessary. See
Figure 37 (page 41) or Figure 38 (page
41)
for component location.
• If the furnace operates when the Blower Limit Switch is
reset, contact a qualified service technician to identify
and repair the problem.
• If the furnace still doesn’t operate, check the Flame Roll-
out Switches and reset if necessary.
• If the furnace operates when the Flame Rollout Switch
is reset, contact a qualified service technician to identify
and repair the problem.
DIAGNOSTIC DESCRIPTION GREEN LED RED LED
Control Fault (No Power) Off Off
L1/Neutral Polarity Fault Flash Flash
1 Hour Lockout Alternating Flash
Normal Operation On On
Pressure Switch Closed Fault On Flash
Pressure Switch Open Fault Flash On
Open Limit Switch Fault Flash Off
DIAGNOSTIC DESCRIPTION YELLOW LED
Low Flame Sensor Signal Continuous Flash
Flame Present On
Table 13. Control Board Fault Conditions
FURNACE COMPONENTS
The descriptions below are various functional components
that affect the operation and shutting down of this furnace.
Some of these components and their locations are shown
in
Figure 37 (page 41) or Figure 38 (page 41). If any
component of the furnace must be replaced, use only factory
authorized replacement parts specified in the Replacement
Parts List provided online.
Condensate Drain Switch: The Condensate Drain Switch
will shut down the furnace if the condensate drain from the
Collector Pan becomes clogged.
Blower Limit Switch: Prevents operation when blower is
not operational.
Flame Sensor: Verifies when a flame has carried over from
the igniter to the opposite end burner. If no flame is detected,
the furnace will shut down within 4 seconds.
Flame Roll-Out Switch: Verifies that the burner flames are
drawn into the heat exchanger tubes. If the burner flames are
not properly drawn into the heat exchanger, the flame roll-out
switch will close the gas valve and initiate the shutdown cycle.
Gas Valve: Controls the flow of gas to the burners. When the
gas valve is energized it automatically opens and regulates
the gas pressure in the manifold.
Inducer Assembly: Vents products of combustion to the
outside.
Pressure Switches: Verifies that the inducer is drawing
the combustion gases through the heat exchanger. The
pressure switch prevents furnace operation with excessive
flue/condensate blockage or improper inducer operation.
Supply Air Limit Switch: Prevents the air temperature
leaving the furnace from exceeding the maximum allowable
outlet air temperature.
DIAGNOSTIC DESCRIPTION RED LED GREEN LED
Control Fault (No Power) Off Off
Normal Operation On On
Motor Fault On Flash
Twin Fault (No Motor Fault) Flash On
Communications Fault Flash Flash
Table 14. Motor Control Board Fault Conditions