Carrier 48DU Installation Instructions Manual page 34

SYMPTOM
Burners will not ignite
Inadequate heating
Poor flame characteristics
Table 10—Troubleshooting Chart Con't- -Gas Furnace Operation
CAUSE
Water in gas line
No power to unit
No 24--v power supply to control circuit
Mis--wired or loose connections
Misaligned spark electrodes
No gas at main burners
Inducer pressure switch not closing
Dirty air filter
Gas input to unit too low
Unit undersized for application
Restricted airflow
Limit switch cycles main burners
Incomplete combustion results in: Aldehyde odors,
carbon monoxide, sooting flame, floating flame
Drain. Install drip leg.
Check power supply fuses, wiring or circuit
breaker.
Check transformer.
NOTE: Some transformers have internal over--
current protection that requires a cool--down peri-
od to reset.
Check all wiring and wire nut connections
Check flame ignition and sense electrode posi-
tioning.
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.
1. Check pressure switch wires, connections,
and tubing. Repair or replace if necessary.
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.
Check rotation of blower, temperature rise of unit.
Adjust as necessary.
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.
5. Inspect heat exchanger for blockage. Clean
as necessary.
34
REMEDY