Air Conditioner
A split system cooling appliance: what each half does and how the two halves have to match.
Safety
What it is
A residential split air conditioner places the compressor and condenser coil outdoors and the evaporator coil indoors, usually above a furnace or inside an air handler. Refrigerant lines connect the two halves and the indoor blower moves building air across the cold evaporator.
How it works
Indoor and outdoor sections of a split system
Cooling is only half the job. As air passes over the evaporator below its dew point, moisture condenses out and drains away. A system that is oversized cools the air quickly, satisfies the thermostat, and shuts off before it removes enough moisture - which is why an oversized system can feel clammy.
What can go wrong
- A dirty condenser coil raises head pressure and cuts capacity.
- Low airflow indoors can freeze the evaporator coil into a block of ice.
- A failed run capacitor keeps the compressor or condenser fan from starting.
- A plugged condensate drain triggers a safety switch or causes water damage.
How to diagnose it
Measure the temperature split across the indoor coil
A small split with good airflow points to a refrigerant or compressor problem.
Verify airflow before touching gauges
Filters, coils and blower speed change every refrigerant reading you will take.
Check capacitor microfarad value under load conditions
A weak capacitor causes hard starting, overheating and nuisance trips.
Symptoms
Practice & Mastery
- Air Conditioner Troubleshooting Scenarios2
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