MG2S Installation Manual

27
10. Inspect the burners for accumulated dust or debris.
If necessary carefully clean them with a soft wire
brush and a vacuum cleaner. IMPORTANT: DO
NOT damage the igniter while cleaning the burner
assembly.
11. Replace all the parts in reverse order that they were
removed.
12. Follow the lighting instructions found on the furnace
door to return the furnace to operation. Verify proper
operation after servicing.
Vent System
WARNING:
Holes in the vent pipe or heat exchanger can
cause combustion products to enter the home.
Replace the vent pipe or heat exchanger if leaks
are found. Failure to prevent the circulation of
combustion products into the living space can
create potentially hazardous conditions including
carbon monoxide poisoning that could result in
personal injury or death.
TROUBLESHOOTING
Check the inlet pipe (if applicable) and outlet pipe to ensure
they are not blocked by debris. Any damaged section
of vent pipe must be replaced, and any obstruction or
blockage must be removed prior to operating the furnace.
Heat Exchanger & Burner Maintenance - The furnace
should operate for many years without soot buildup in the
flue passageways, however, the flue, vent system, and
burners should be inspected and cleaned (if required) by
a qualified service technician annually to ensure continued
safe operation. Pay attention to any deterioration from
corrosion or other sources.
Lubrication - The bearings in the blower motor and
inducer blower used in these furnaces are pre-lubricated
and sealed by the manufacturer. No further oiling of the
bearings is required for the life of the motor.
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?
Furnace Control Board
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
Motor Fault On Off
Diagnostic Description Yellow LED
Low Flame Sensor Signal Continuous Flash
Flame Present On
Motor Control Board (Variable Speed)
DIAGNOSTIC
DESCRIPTION
Green
LED
Red
LED
Control Fault (No Power) Off Off
Normal Operation On On
Motor Fault On Flash
Communications Fault Flash Flash
Table 5. Control Board Fault Conditions
• 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 5 below or the wiring diagram
(Figure 28, page 33) 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. For component locations see Figure 22
(page 28).
• 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 switch 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.