A/C & Heat Pumps
~12 min read · Use temperature split, condensate and refrigerant-line clues to judge cooling systems.
Cooling inspection is performance reading without gauges: the temperature split across the coil, the condensate's escape route, and the outdoor unit's health. Add the rule about not running compressors in cold weather, and the section is complete.
The temperature split
Operate in cooling mode and measure supply-vs-return air temperatures: a healthy system drops roughly 14–20°F across the evaporator. Low split: low refrigerant charge, weak compressor, or excessive airflow; high split: starved airflow (filter, blower, iced coil). It is a screening number, not a diagnosis — report out-of-band splits with 'HVAC evaluation.' Frozen suction lines and ice on the coil are report-now findings (run in fan-only to confirm airflow issues vs charge). Operating limitation: don't run compressors when outdoor temps have been below ~60–65°F (oil migration damages them) — state the limitation instead of testing on winter inspections.
- 14–20°F supply/return split = the screen
- Ice on lines/coil: stop-and-report
- Cold-weather no-test rule — state the limitation
Condensate management
Cooling wrings gallons from the air; that water needs a safe exit: primary drain trapped and flowing (algae clogs are the service call of summer), and for units above living space, a secondary/auxiliary pan with its own drain to a conspicuous location OR a float switch that kills the unit before overflow — the ceiling-stain-under-the-attic-air-handler pattern is this system failing. Condensate pumps: function and discharge routing. Rust and water in/under the air handler mark history.
- Primary drain trapped, clear, flowing
- Overhead units: aux pan + drain or float switch
- Ceiling stains below air handlers tell the story
Outdoor unit and heat pumps
The condenser: coil condition (fins matted with cottonwood; bent fin fields), clearance for airflow, level pad, refrigerant line insulation (suction line armaflex sun-rotted), disconnect present, and the data plate (age; R-22 units flag the refrigerant-phaseout economics — repairs on borrowed time). Heat pumps add: reversing operation (heat and cool), defrost behavior, supplemental heat strips, and the same split logic in heating (smaller, warmer split). Age framing: compressors live ~10–15+ years; the report gives age and condition, not warranties.
Worked example
August inspection: the system runs but the house is muggy; the split measures 8°F; the outdoor coil wears a fur coat of cottonwood; the suction line's insulation is missing for six feet of sun exposure; and in the attic, the air handler's secondary pan holds rusty water with no float switch visible — the ceiling below shows a tea-colored ring. Diagnose the layers.
The 8°F split confirms the mugginess — underperforming. Candidate causes visible without gauges: the furred condenser can't reject heat (airflow blockage — cleaning is step one), and the bare, sun-cooked suction line adds gains; charge state needs an HVAC tech's gauges — referral with the split documented. The attic: rusty water IN the secondary pan means the primary drain has already failed at least once; no float switch means the next failure goes through the ceiling — the existing ring says it already has. Report: performance deficiency with visible contributors (clean coil, insulate line, evaluate charge), condensate primary blocked (service), aux protection incomplete (add float switch/drain), moisture history noted. Screen, contributors, referral — the cooling method in one house.
Common exam pitfalls
Reporting the split as a refrigerant diagnosis.
The split screens; gauges diagnose — report out-of-band numbers with evaluation referrals.
Running the compressor on a cold day to 'be thorough.'
Cold-start damage is real — state the weather limitation and move on.
Passing an attic unit with a dry primary and no float switch.
Aux protection is for the day the primary clogs — absent pan/drain/switch above living space is a finding even when dry.
Fourteen-to-twenty across the coil, water finds its drain, and compressors sleep through cold weather.
Recap
- Split screen 14–20°F; ice = stop-and-report
- Cold-weather compressor no-test limitation
- Condensate: trapped primary; aux pan/drain or float above ceilings
- Condenser airflow, fins, line insulation, disconnect
- R-22 era units: phaseout economics note
- Heat pumps: both modes, defrost, strips
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