29
Table 8 -- Troubleshooting Chart (Cont’d)
SYMPTOM
CAUSE
REMEDY
Burners will not ignite
Water in gas line
Drain. Install drip leg.
No power to furnace
Check power supply fuses, wiring or circuit breaker.
No 20--v power supply to control circuit
Check transformer.
NOTE: Some transformers have internal over--current
protection that requires a cool--down period to reset.
Mis--wired or loose connections
Check all wiring and wire nut connections
Burned--out heat anticipator in thermostat
Replace thermostat
Broken thermostat wire
Replace thermostat
Burned--out heat anticipator in thermostat
Run continuity check. Replace wire if necessary.
Misaligned spark electrodes
Check flame ignition and sense electrode positioning. Ad-
just as necessary
No gas at main burners
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 attempting to light unit.
2. Check gas valve.
Inadequate heating
Dirty air filter
Clean or replace filter as necessary
Gas input to furnace too low
Check gas pressure at manifold match with that on unit
nameplate
Unit undersized for application
Replace with proper unit or add additional unit
Restricted airflow
Clean or replace filter. Remove any restriction.
Blower speed too low
Use faster speed tap if available, or install alternate motor.
Limit switch cycles main burners
Check rotation of blower, temperature rise of unit. Adjust
as necessary.
Poor flame characteristics
Incomplete combustion results in: Aldehyde odors, carbon mon-
oxide, sooting flame, floating flame
1. Tighten all screws around burner compartment
2. Cracked heat exchanger. Replace.
3. Unit over--fired. Reduce input (change orifices or adjust
gas line or manifold pressure).
4. Check burner alignment.
604D
