How to tell if my AC was installed correctly

Wondering whether your new air conditioner was installed the right way? A correct installation is the difference between years of efficient comfort and a string of breakdowns. Below is a plain‑English checklist you can use at home to spot signs of quality workmanship, plus the critical code and documentation pieces that prove the job meets standards. Where hands‑on testing involves electricity, refrigerant, or ladder work, avoid DIY risks—many insurance policies and warranties expect certified HVAC involvement.

Immediate comfort and airflow

Within minutes of startup, your home should begin cooling steadily without hot or cold blasts. Supply registers should push a strong, consistent stream of air, and returns should pull air quietly. Rooms at the far end of runs shouldn’t feel starved for airflow. Weak airflow or whistling often points to undersized returns, crushed flex ducts, or poor balancing.

Temperature split you can measure

Use a simple thermometer. After 10–15 minutes of continuous cooling, the air temperature at a supply register should typically be about 16–22°F lower than at the nearest return (delta‑T). A very low split can indicate low refrigerant charge, high static pressure, or a dirty filter; a very high split can hint at restricted airflow or coil icing.

Quiet, low‑vibration operation

Indoors, you should hear a smooth hum—no buzzing, rattles, or door‑shaking vibrations. Outdoors, the condenser should sit level on a pad with anti‑vibration feet or a properly anchored stand. Persistent rattles suggest loose panels, misaligned blower wheels, or line set contact with framing.

Even temperatures room to room

Good installs balance supply and return air. Bedrooms should not be several degrees warmer than hallways. If balancing dampers were set, rooms should feel consistent throughout the day. Hot spots often mean poor duct design, bad transitions, or insufficient return air in closed‑door bedrooms.

Clean condensate drainage

The drain line should have a continuous downhill slope to the outlet, a clean trap if required, and no visible leaks. In attics or closets, you should see a secondary drain pan and a float safety switch that shuts the system off if water rises—this protects ceilings and meets common insurance expectations.

Refrigerant line set and charge basics

You won’t handle refrigerant yourself, but you can spot install quality. Line sets should be insulated end‑to‑end, UV‑protected outdoors, and neatly secured with no kinks. A pro install includes a nitrogen pressure test, a deep vacuum (often to 500 microns), and charge verified by superheat/subcooling to manufacturer specs. Frost on lines or the coil is not normal in cooling mode.

Electrical and safety

There should be a weatherproof disconnect within sight of the outdoor unit, correct breaker size per the unit nameplate, proper wire gauge, and solid grounding. The indoor unit should have a service switch. Overfused or underfused circuits are red flags. Low‑voltage thermostat wiring must be cleanly landed and protected from sharp metal.

Thermostat placement and setup

The thermostat should be away from supply vents, direct sun, ovens, or exterior doors. Staging and fan settings should match the system type. For high‑efficiency equipment, a common wire (C‑wire) is preferred for stable power. Poor placement causes short cycling and wide temperature swings.

Duct sizing, sealing, and static pressure

Quality installs keep total external static pressure within manufacturer limits (commonly around 0.5 in. w.c.). Returns must be generous, filter racks should seal tightly with no bypass, and joints should be sealed with mastic—not just tape. In hot attics, insulation values (e.g., R‑8) and short flex runs protect performance.

Proper system sizing (no guesswork)

Installers should reference a load calculation (Manual J) and match equipment using AHRI‑verified combinations. Oversized systems short‑cycle, create humidity issues, and waste energy; undersized equipment struggles on hot afternoons and drives up bills.

Permits, code, and documentation

In California, permitted installs are the norm. Ask for the permit number, inspection sign‑off, and Title 24/HERS documentation where applicable (duct leakage, airflow, and refrigerant charge verification). You should receive an AHRI certificate, model/serial numbers, warranty registration confirmation, and a commissioning report. Insurance carriers and manufacturers often require licensed installation and proper paperwork for coverage.

Energy bills and performance trend

During the first month, note runtime and bills relative to prior seasons. For a comparable weather period, a correctly installed SEER2‑rated system should track close to projections given your home size and insulation. Large deviations can indicate airflow or charge issues.

Odors and indoor air quality

A brief “new equipment” or dusty smell can be normal on first runs. Persistent chemical, musty, or burning odors are not—these can signal electrical issues, a blocked drain, or a refrigerant problem. Filtration should be sized correctly (often MERV 11–13 for homes) with no air bypass around the filter.

Outdoor unit clearances and location

Check for 12–24 inches of clear space around the condenser and full clearance above. Avoid roof drip lines, dryer vents, and tight alcoves that recirculate hot exhaust air. Plants and fences should not block coil airflow.

Mini‑split specifics

Flare joints must be properly torqued, lines neatly routed in a line‑hide, and condensate from each head pitched to drain or pumped with a trap‑free run. Indoor heads should be level, with quiet operation on all fan speeds and no water drips on long cycles.

Day‑one and week‑one homeowner checks

• Confirm delta‑T near 16–22°F after steady operation.
• Verify no water drips at the air handler or secondary pan.
• Listen for smooth fan starts and stops—no rattles.
• Ensure filter is new, correctly sized, and sealed.
• Walk rooms for even comfort and balanced airflow.
• Locate the outdoor disconnect and indoor service switch.
• Collect permit, AHRI match, and warranty paperwork.

When to involve a professional

High voltage, pressurized refrigerants, and ladder work are hazardous. Adjusting charge, measuring static pressure, setting blower speeds, or sealing ducts inside attics should be handled by qualified technicians. Many warranties and insurers require licensed documentation for claims—DIY fixes can put coverage at risk.

Who we are

#1 AC Guys is a family HVAC company in Southern California, serving Los Angeles County and nearby areas including Orange County, Ventura County, and Western Riverside County (examples: Los Angeles, Long Beach, Pasadena, Glendale, Burbank, Santa Clarita, Anaheim, Irvine, Santa Ana, Oxnard, Thousand Oaks, Corona, Temecula, and more). Our fourth‑generation family of engineers brings 80+ years of engineering experience to residential and commercial projects, with a special focus on large and complex systems. Our mission is healthy air at home for a healthier life.

Our engineers trained at manufacturer facilities for Fujitsu (Japan), Mitsubishi Elektrik (Thailand), Midea (China), Gree (China), and Hier (China). That grounding in factory methods informs our commissioning: load calculations, pressure testing with nitrogen, deep‑vacuum evacuation, airflow and static tuning, verified charge, and documented results you can keep for your records.

Bottom line

If your AC cools evenly and quietly, drains cleanly, shows a healthy temperature split, carries proper permits and paperwork, and passes basic visual checks, it was likely installed correctly. If any critical item is off—especially electrical protection, drainage, refrigerant charge, or code compliance—stop and have a qualified HVAC professional evaluate before damage or insurance problems arise.