Carrier 48GH - Manual (Page 21)

TROUBLESHOOTING CHARTS
Table 7 — Heating Service Analysis Chart
SYMPTOM
Pilot Will Not Light
Burners Will Not Ignite
Inadequate Heating
Poor Flame Characteristics
CAUSE No spark at electrode
Spark shorting out to main
burner ____ __
No gas at pilot burner
Water in gas line
No power to furnace
No 24-volt power supply to
control circuit_________
Miswired or loose connections
Dirty pilot — yellow flame
Pilot burning properly —
sharp blue flame_____
Burned out heat anticipator
in thermostat______ ___
No gas at main burners
REMEDY
Check air gap between electrode tip and pilot
burner Gap should be as shown in Fig. 10
Readjust as necessary. _ _____
Clean moisture or dirt accumulation on electrode
ceramic with cloth._____ __________
Cracked ceramic — replace pilot electrode
assembly. _ ______ _____________
Check for loose or broken wiring at and between
spark generator and electrode. Replace wire or
tighten connection as necessary. ______
Check fuses or circuit breaker to ensure voltage
to unit.
Check 24-volt input to spark generator If you read
24 volts and above steps have been completed,
replace spark generator. _ _____
Realign electrode tip away from main burner but
maintain spark gap to pilot burner. See Fig. 10.
Clean pilot orifice.__ ________ _
Check for voltage to terminals 3 and 5 of
gas valve. ____
Check to see if pilot valve is opening Check for
loose or broken wiring connections If no
deficiency is found, replace gas valve___
Drain — install water trap.____________ _
Check power supply, fuses, wiring, or circuit
breaker._______________________ ___
Check transformer — replace if necessary
Check all wiring amd wirenut connections.
Clean pilot orifice.
Replace pilot
Replace thermostat
Broken thermostat wire
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, (CO), sooting
flame — floating flame
Check to see if main gas valve is opening. Look
for loose or broken wiring connections If no
deficiency is found, replace valve assembly.
Run continuity check to locate break._ __
Replace filter. __________ ______
Check gas pressure at manifold Clock gas meter
for input. If too low, increase manifold pressure
or replace with correct orifices.
Replace with proper unit — or add additional unit.
Clean or replace filter — or remove any
restriction. _______ _________ ________ _
Use faster speed tap — or install optional blower.
Dirty air filters — clean or replace.____
Registers closed, restricted ductwork — open or
remove restriction.
Check heat anticipator setting on thermostat —
readjust._ _ __ _____ _____ ___
Air shutters on burners closed — adjust to
soft blue flame. __________________ ____
Check all screws around flue outlets and burner
compartment — tighten. _ __
Lack of combustion air.................................
Cracked heat exchanger — replace.______
Overfired furnace — reduce input or change
orifices._________ ________ ___ ______
Check vent for restriction — clean as required.
Check orifice to burner alignment.
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