Carrier 48XL SYMPTOM Burners will not ignite, Inadequate heating Poor flame characteristics

SYMPTOM

Burners will not ignite

Inadequate heating

Poor flame characteristics

Table lO--Troubleshooting Chart Con't-Gas Furnace

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

Operation

REMEDY

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.

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