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SYMPTOM
Burners will not ignite.
Inadequate heating.
Poor flame characteristics.
Heating
CAUSE
Water
in gas line
No power
to furnace
No 24-v
power
supply
to control
circuit
Miswired
or loose connections
Burned-out
heat anticipator
in
thermostat
Broken
thermostat
wire
Misaligned
spark
electrodes
No gas at main
burners
Dirty air filter
Gas input to furnace
too low
Unit undersized
for application
Restricted
airflow
Blower
speed
too low
Limit switch
cycles
main
burners
incomplete
combustion
results
in:
Aldehyde
odors,
carbon
monox-
ide, sooting
flame,
floating
flame
REMEDY
Drain.
install
drip leg.
Check
power
supply
fuses,
wiring,
or circuit
breaker.
Check
transformer.
NOTE:
Some
transformers
have internal
overcurrent
protection
that requires
a cool-down
period
to reset.
Check
all wiring
and wirenut
connections.
Replace
thermostat.
Run continuity
check.
Replace
wire if necessary.
Check
flame
ignition
and sense
electrode
positioning.
Adjust
as necessary.
1. Check
gas line for air. Purge
as necessary.
NOTE:
After
purging
gas line of air, wait at least
5 minutes
for any gas to dissipate
before
attempt-
ing to light unit.
2. Check
gas valve.
Clean
or replace
filter as necessary.
Check
gas pressure
at manifold.
Match
with that on
unit nameplate.
Replace
with proper
unit or add additional
unit.
Clean
or replace
filter. Remove
any restriction.
Use faster
speed
tap if available,
or install
alternate
motor.
Check
rotation
of blower,
thermostat
heat antic-
ipator
settings,
temperature
rise of unit. Adjust
as
necessary.
1. Tighten
all screws
around
burner
compartment.
2. Cracked
heat exchanger.
Replace.
3. Unit overfired.
Reduce
input (change
orifices
or
adjust gas line or manifold
pressure).
4. Check
burner
alignment.
--35--
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