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Table 28 -- Heating Service Analysis
PROBLEM CAUSE
Burners Will Not Misaligned spark electrodes.
Ignite.
No gas at main burners.
Water in gas line.
No power to furnace.
No 24 v power supply to control circuit.
Miswired or loose connections.
Burned-out heat anticipator in thermostat.
Broken thermostat wires.
Inadequate Heating, Dirty air filter.
Gas input to unit too low.
Unit undersized for application.
Restricted airflow.
Blower speed too low.
Limit switch cycles main burners.
Too much outdoor air.
Poor Flame
Characteristics.
Incomplete combustion (lack of combustion air)
results in:
Aldehyde odors, CO, sooting flame, or floating flame.
Burners Will Not Turn Unit is locked into Heating mode for a one minute
Off. minimum.
Table 29 -- MoistureMi$er TM Dehumidification Subcooler Service Analysis
PROBLEM CAUSE
Subcooler Will Not Energize No power to subcooler control transformer.
REMEDY
Check flame ignition and sensor electrode positioning.
Adjust as needed.
Check gas line for air; purge as necessary. After purging
gas line of air, allow gas to dissipate for at least 5 min-
utes before attempting to relight unit.
Check gas valve.
Drain water and install drip leg to trap water.
Check power supply, fuses, wiring, and circuit breaker.
Check transformer. Transformers with internal overcur-
rent protection require a cool-down period before
resetting. Check 24-v circuit breaker; reset if necessary.
Check all wiring and wire nut connections.
Replace thermostat.
Run continuity check. Replace wires if necessary.
Clean or replace filter as necessary.
Check gas pressure at manifold. Check gas meter for
input. If too low, increase manifold pressure or replace
with correct orifices.
Replace with proper unit or add additional unit.
Clean filter, replace filter, or remove any restrictions.
Install alternate motor, if applicable, or adjust pulley to
increase fan speed.
Check rotation of blower, thermostat heat anticipator set-
tings, and temperature rise of unit. Adjust as needed.
Adjust minimum position.
Check economizer operation.
Check all screws around flue outlets and burner com-
partment. Tighten as necessary.
Cracked heat exchanger.
Overtired unit -- reduce input, change orifices, or adjust
gas line or manifold pressure.
Check vent for restriction. Clean as necessary.
Check orifice to burner alignment.
Wait until mandatory one-minute time period has
elapsed or cycle power to unit.
Subcooler Will Not Deenergize
Low System Capacity
No power from subcooler control transformer to
liquid line three-way valve.
Liquid line three-way valve will not operate.
Liquid line three-way valve will not close.
Low refrigerant charge or frosted coil.
REMEDY
Check power source. Ensure all wire connections
are tight.
1. Fuse open; check fuse. Ensure continuity of wiring.
2. Subcooler control low-pressure switch open.
Cycle unit off and allow low-pressure switch
to reset. Replace switch if it will not close.
3. Transformer bad; check transformer.
1. Solenoid coil defective; replace.
2. Solenoid valve stuck closed; replace.
Valve is stuck open; replace.
1. Check charge amount. See system charging
section.
2. Evaporator coil frosted; check and replace
subcooler control low-pressure switch if necessary.
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