Key takeaways
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Checklist = fewer errors, better warranties.
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Do Manual J load calc before picking equipment.
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Use AHRI-matched parts + NEC rules for safety.
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Level outdoor unit with 3+ ft clearance + drainage.
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Seal ducts with mastic, test + balance airflow.
Why this checklist matters (and how it saves you money)
Most comfort problems start on day one. If the system is too big, it cools fast but leaves sticky air. If ducts leak, you pay to cool the attic. This practical checklist gives homeowners and contractors a shared plan—from planning to final testing—so your system runs safely, quietly, and efficiently for years. It follows U.S. best practices (ACCA, AHRI, NEC) and uses simple steps you can verify.
Common problems this checklist solves
Here are the issues we see most in U.S. homes:
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Wrong size equipment → short cycling, poor humidity control, high bills.
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Leaky or undersized ducts → noisy vents, uneven rooms.
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Messy line-set work → refrigerant leaks later.
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Skipped commissioning → no one verifies performance numbers.
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Missing paperwork → weakened warranties.
This checklist fixes those by putting the steps in the right order: measure the house first, match components, prepare safe work areas, install cleanly, and then prove performance with numbers. When pros follow this flow, call-backs drop and comfort improves. For quick context on installation pitfalls, skim our recent overview on central air install phases and common errors; it matches what you’ll check off here.
Pre-install planning: site assessment & Manual J
Start with a room-by-room look at the home. Measure square footage and ceiling heights, note insulation, window size and direction, and count people and appliances that add heat. Then run Manual J—the ACCA method that calculates exactly how many BTU/h your home needs in real U.S. weather, not guesses. It prevents the common “too big” trap. Bring this to the design table:
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Target tonnage and sensible/latent loads by room.
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Outdoor design temps for your ZIP code.
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Notes on problem rooms (bonus rooms, west-facing glass).
If you want a simple walkthrough plus a template, see Manual J basics and our downloadable AC sizing guide. Or talk with our Design Center if you’d like a second set of eyes.
Helpful links: Sizing Guide, Design Center
Pick the right equipment: AHRI matches & R-32 readiness
Choose equipment based on the Manual J results—not rules of thumb. Verify indoor and outdoor units are AHRI-matched so published efficiency and capacity hold true (and warranties stay valid). In 2025, many residential systems use R-32 refrigerant for better efficiency and lower global-warming potential than older blends. If you’re shopping components, browse our [R-32 condensers], compatible [AC & coils], or packaged options. For plain-language primers on R-32 safety and benefits, start here: R-32 overview and A2L safety basics. These explain performance and handling in a homeowner-friendly way.
Helpful links: R-32 Residential Condensers, R-32 AC & Coils,
Safe setup: work area, power-off, and U.S. code basics
Clear paths to the furnace/air handler, attic or crawlspace, and the outdoor pad location. Protect floors, cover furniture, and stage tools. Then lock out and tag out the breaker feeding the HVAC equipment. Verify with a meter that power is off before touching conductors. In the U.S., follow the National Electrical Code (NEC)—especially Article 440 for HVAC. Use the correct wire gauge, install a weatherproof disconnect within sight of the condenser, and ground everything properly. Inside, plan space for service access: filters, coil doors, and drain clean-outs should not be blocked. If you’re replacing an air handler, compare specs and dimensions from our Air Handlers section and make sure supply/return transitions won’t choke airflow. For common pre-job prep tips, see our step-by-step central air overview
Helpful links: Air Handlers, Help Center
Outdoor unit placement: pad, clearance, and drainage
Set a level concrete or composite pad on compacted soil or pavers. Keep 3 feet or more of open space on all sides and clear sky above for airflow and service. Avoid direct roof runoff; slope grade so rain moves away from the pad. In snowy regions, raise the unit on risers. Keep shrubs trimmed and grills or dryers at a distance to prevent hot exhaust recirculation. Route the line set with gentle bends, protect it in UV-resistant insulation, and plan a tidy whip and low-voltage entry. If you’re selecting equipment that fits your location and budget, see our and financing options to keep projects moving without cutting corners on site work. For more homeowner prep reminders before install day, review our pros & cons checklist article.
Helpful links: R-32 Residential Packaged Air Conditioners, HVAC Financing
Ductwork design & sealing: quiet, even airflow
Ducts are the “roads” your air travels. Design with Manual D principles: target about 400 CFM per ton, limit sharp turns, and size returns generously. Support ducts every 4–6 feet and insulate any runs in attics or crawlspaces. Seal every joint with mastic (not tape alone) and then pressure-test for leakage. After start-up, balance each room by measuring supply CFM and adjusting dampers so rooms land near design airflow. These steps reduce noise and hot/cold spots and protect efficiency. For a homeowner-friendly primer on duct design and airflow fixes, read Ductwork Design Basics—it shows how right-sized, sealed ducts boost comfort and lower bills. If you’re comparing system types for tricky layouts, explore Ductless Mini-Splits
Refrigerant lines & brazing: clean, leak-free connections
Install the line set as a single, unbroken run sized to the manufacturer’s chart. Support copper every 4–6 feet and protect it from sharp edges. Insulate the suction line fully; the liquid line is typically bare. When joining, braze—don’t solder—and purge nitrogen (3–5 CFM) the whole time to prevent oxidation flakes that can clog TXVs. Heat the joint evenly and use a silver-bearing alloy (≈15% Ag). Let joints cool naturally, then pressure-test with dry nitrogen and evacuate the system to ≤500 microns before opening the refrigerant. A tidy line set and dry, clean system are the difference between years of smooth operation and early failures. If you need materials, see our Line Sets and Accessories sections for U.S.-standard parts that match today’s R-32 systems.
Electrical, commissioning, warranty & handover: prove it with numbers
Tighten lugs to spec, confirm correct breaker/fuse sizes, and verify the disconnect. On start-up, record suction/liquid pressures, superheat/subcooling, compressor amps, and supply/return temperatures. Measure total external static pressure and compare to the blower chart; adjust fan speed or duct restrictions if needed. Balance registers so each room gets its design CFM. Finally, document serial numbers, test results, and thermostat settings; register warranties within the required window and schedule the first checkup. Homeowners should know filter sizes and how to change them, how to set schedules, and when to call for service. For friendly refreshers, see our central air install tools & steps recap, then dive deeper into Manual J and R-32 resources when you want the “why” behind the numbers
FAQs (quick answers)
How long does a standard central air install take?
Usually 1–2 days once materials are on site. Complex duct fixes can add time. (Always plan for testing at the end.)
Do I really need Manual J?
Yes. It’s how pros right-size equipment for your exact home and climate, preventing humidity and short-cycling issues. See our Manual J basics.
What clearances does the outdoor unit need?
Keep about 3 feet on all sides and good airflow above. Avoid standing water and aim for shade if possible.
Tape or mastic on ducts?
Mastic (plus mesh on big seams) is the dependable, long-term seal. Then pressure-test and balance.
Why do techs “pull a vacuum” to 500 microns?
It removes moisture and air so refrigerant flows cleanly and the compressor lasts.
Is R-32 safe for homes?
Yes when installed by EPA-certified pros and used as designed. Read our R-32 safety explainer
What paperwork should I keep?
Model/serial numbers, test results, permits, warranty registration, and a simple maintenance log (filters, service dates).
