Hey There, Cool Customer 😎
It’s your girl Samantha again, here to save you from another round of HVAC headaches. You’ve done your homework, picked out the perfect central air conditioning system (hopefully from my personal fave spot, The Furnace Outlet 💁), and you’re ready to dive into installation.
Buuut hold up. Before you grab a screwdriver or sign off on a contractor, let’s talk about the most common mistakes I see homeowners make when installing central AC systems. Because nothing ruins summer faster than blowing your budget and your cool.
Let’s make sure your comfort upgrade goes off without a hitch. Ready? Let’s do this. 🔧❄️
1. Skipping a Load Calculation
Too many folks skip proper sizing and assume "bigger is better" (spoiler alert: it’s not). If your unit is too big, it’ll cycle too quickly and leave your home humid. Too small? It’ll run nonstop and still won’t cool effectively.
You need a proper Manual J load calculation done for your home’s size, insulation, and climate. Many pros (and DIYers) guess at this and get it way wrong.
Want to understand how it’s calculated? This HVAC load calculator by Service Titan is a good intro to how the pros do it.
2. Not Sealing Ducts Properly
You could buy the most efficient unit on the market, but if your ducts are leaking like a colander, guess what? You're paying to cool your attic.
Make sure all ductwork connections are sealed with mastic, not just duct tape. According to the U.S. Department of Energy, the average home loses up to 30% of airflow due to leaky ducts. That’s like throwing money out the window.
3. Installing the Thermostat in a Bad Spot
The thermostat is your system’s brain. Place it near a window or a vent and it’ll get confused, thinking it’s cooler (or hotter) than it actually is. That means uneven cooling and nonstop cycling.
Ideal placement? A central, interior wall—away from direct sunlight, vents, or appliances. Trust me, this little sensor needs a drama-free zone. 🧠📍
4. Forgetting to Check Local Codes and Permits
I know, paperwork is no one’s idea of a good time—but installing a central AC system without the right permits is asking for trouble. Not only can it affect your resale value, but you might get hit with fines or be forced to redo the whole thing.
Double-check your municipality's permit requirements or talk to your HVAC pro. Many states now require documentation, especially for energy efficiency standards. The International Code Council is a great place to see what’s current.
5. Overlooking Drainage and Condensate Lines
Your AC system doesn’t just cool—it pulls moisture from the air. That water needs to go somewhere or you’ll end up with soggy ceilings or mildew in your basement.
Make sure your condensate line is clear and slopes away from the home. Bonus points for adding a secondary drain pan and a float switch, which can shut off the unit before it floods.
6. Using the Wrong Refrigerant or Connections
Today’s systems are often built for R-32 or newer refrigerants. If you’re retrofitting, mixing refrigerants or using outdated gauges can void your warranty—or worse, ruin your compressor.
Your system manual should state exactly what refrigerant it uses, and your installer should have recovery tools on hand. ASHRAE is a go-to source for understanding safe refrigerant handling, especially with newer low-GWP options.
7. Ignoring the Airflow Setup
A shiny new system won’t mean squat if your airflow is off. Things like improperly sized return ducts, dirty vents, or backward blower installation (yes, it happens 🙈) can destroy efficiency.
Always test airflow at vents using a simple anemometer or ask your tech to do a static pressure test. Low airflow = higher bills, lower comfort.
8. Hiring Based on Price, Not Credentials
Look, I love a good deal. But AC installation isn’t a Groupon kind of job. Hiring a cheap, unlicensed installer can cost you thousands in rework.
Make sure your HVAC tech is NATE-certified, insured, and experienced. You can check contractor reviews and licensing status at the Better Business Bureau.
9. Skipping a Final System Test
You’d be shocked how many systems get installed and never properly tested. Always ask for a full system check: airflow, refrigerant pressure, voltage, and a thermostat calibration.
If something seems off—noisy ducts, inconsistent cooling, weird smells—call it out. This is your home, not an experiment.
10. Not Registering Your Warranty
This is such an easy step, and yet people miss it all the time. Most major brands require you to register your system within 60–90 days or the warranty gets cut in half.
Keep all your paperwork, register the product online, and understand what’s covered. You can usually do this right on the manufacturer’s website. And trust me—you’ll thank yourself later.
Final Word from Samantha ☀️
I’ve said it before, and I’ll say it again: AC is an investment. And like any good investment, it deserves thoughtful planning, quality parts, and expert care. Avoiding these mistakes can mean the difference between a comfy, carefree summer and a $5,000 regret.
And if you’re still in the market for your system, don’t forget to check out my go-to source: The Furnace Outlet’s central AC bundles. They’ve got quality systems at down-to-earth prices—just the way I like it.
Having low airflow issues with your central AC? Visit my guide: Feeling the Breeze... or Not?
Catch you on the cool side. ❄️💃
- Samantha, Home Comfort Advisor
