32
Table13 – He ating Service Analysis
PROBLEM CAUSE REMEDY
Burners Will Not Ignite.
Misaligned spark electrodes. Checkflam e ignition and sensorelectrode positioning.
Adjust as needed.
Nogas at m ain burners.
Checkgas line for air, purge as necessary. After purging
gas line of air,allow gas to dissip ate for at least 5 minutes
before attempting to relight unit.
Checkgas v alve.
Water in gas lin e. Drainwater and install drip leg to trap water.
Nopower to furnace. Check power supply,fuses, w iring, and circuit breaker.
No 24 v power supply to control
circuit.
Checktra nsformer.Transformers with internal overcurrent
protectionrequire a cool down period before resetting.
Miswired or loose connections. Checkall wiring and wire nut connections.
Burned---outh eat anticipator in
thermostat. Replace thermostat.
Broken thermostat wires. Run continuity check. Replace wires, if necessary.
InadequateH eating.
Dirtya ir filter. Cleanor replace f ilter as necessary.
Gasinput to unit too low.
Checkgas pressure at m anifold. Clock gas meter for input.
If too low,increase ma nifold pressure, or replace with
correctorif ices.
Unitundersized forapplication. Replace with proper unitor add additional unit.
Restricted airflow. Clean filter,replace filter, or remove any restrictions.
Blower speed too low. Usehigh speed tap, increase fan speed, or install optional
blower,as suitable for individual units.
Limitswitchcyclesmainburners. Checkrotation of blower, thermostatheat anticipator
settings, and temperature rise of unit. Adjust as needed.
Toomuch outdoor air. Adjust minimumposition.
Check economizer operation.
PoorFl ame
Characteristics.
Incomplete combustion (lack of
combustion air) results in:
Aldehyde odors, CO, sooting
flame,or floating flame.
Checkall screws around flue outlets and burner
compartment. Tighten as necessary.
Crackedheat exchanger.
Overfired unit — reduce input, change orifices, or adjust
gasline or manif old pressure.
Checkvent f or restriction.Clean asnecessary.
Checkorifice to bu rner alignment.
Burners Will Not Turn
Off.
Unitis locked into H eating mode
fora one minute m inimum.
Waituntil mandatory one ---minutetime period has elapsed
orre set power to unit.
48TC