At Shellaby AC & Refrigeration, we understand that installing a new HVAC system is a major investment. A poor installation can lead to higher bills, reduced comfort, frequent repairs, or a short system lifespan. In this guide, we’ll walk you through 8 common HVAC installation mistakes that homeowners (and even contractors) often make — so you can spot red flags, ask the right questions, and protect both your comfort and your wallet. Whether you’re looking for HVAC Installation in Corpus Christi TX, or residential HVAC installation elsewhere, knowing these pitfalls will help you get a smoother, better-performing system from day one.
1. Wrong Sizing of HVAC Equipment
One of the most critical mistakes is picking a unit that’s too big or too small. An oversized system will short cycle (turn on and off too quickly), causing inefficient performance, high energy use, and wear on components. A system that’s too small will struggle to meet demand, leaving some rooms undercooled or overheated and pushing the system beyond its limits. HVAC experts often point out that improper sizing ranks among the top installation errors.
To avoid this, a reputable contractor should perform a load calculation (Manual J or similar) factoring in insulation, window sizes, orientation, occupancy, and more. Don’t accept a guess or a rule-of-thumb sizing. At Shellaby AC & Refrigeration, we always start with a precise load analysis, whether for air conditioning installation in Corpus Christi or heating services elsewhere.
Symptoms of wrong sizing:
- System cycles very frequently
- Rooms struggle to reach set temperature
- Uneven comfort zones
- Noisy starts and stops
If you already have an install and suspect sizing issues, request the load calculation and compare it to the unit’s rated capacity. If there’s a mismatch, you may need to correct it early, rather than putting up with elevated energy bills and more repairs.
2. Improper Duct Design or Sealing
Your HVAC system is only as good as its ductwork. Even with a perfect unit, poor duct design or leaks will waste energy and ruin performance. Many installations skip careful duct planning, leading to:
- Undersized trunks or runs
- Long, convoluted duct paths
- Poor transitions or sharp bends
- Leaky seams or joints
- Inadequate insulation
These flaws cause lost airflow, pressure imbalances, and wasted energy.
A few rules to keep in mind:
- Ensure all joins, seams, and connections are sealed with proper materials (mastic, UL-approved tape)
- Size each run to maintain balanced airflow
- Avoid sharp angles and excessive bends
- Insulate ducts in unconditioned spaces
When we handle duct cleaning and ventilation service or HVAC maintenance solutions, we often uncover leaks or gaps that have undermined performance from day one.
3. Poor Placement of Indoor and Outdoor Units
Where you place the outdoor condenser, indoor air handler, or thermostat matters more than most people realize. Mistakes include:
- Outdoor unit too close to walls or obstacles, restricting airflow
- Indoor unit in areas with poor airflow or obstruction
- Thermostat mounted near heat sources or in direct sunlight
If the outdoor condenser is boxed in, crowded against walls, or near shrubs, it can’t exhaust heat effectively. The indoor unit needs clearance too. Thermostat placement in a hot corner or in direct sun leads to false readings that force your system to overwork.
At Shellaby AC & Refrigeration, we always check airflow paths and space requirements. Be sure that your contractor considers unit clearance and ventilation, not just electrical wiring.
4. Faulty Electrical Work & Improper Wiring
The electrical side of an HVAC installation is often overlooked, yet mistakes here can be dangerous or costly. Some common errors include:
- Undersized wiring for power loads
- Poor grounding or missing ground
- Wrong fuse or breaker sizing
- Loose connections or weak contacts
- Mixing voltage phases or motors
These issues can cause voltage drops, frequent fuse blows, or even damage to compressors and control boards.
Always ensure that the electrician or HVAC technician follows manufacturer instructions, local codes, and verifies voltages once installed. Also, ask to see the post-install electrical testing and documentation—something we routinely provide at Shellaby AC & Refrigeration.
5. Skipping Proper Refrigerant Charge & Leak Testing
An HVAC system only works right when it has the correct refrigerant charge and is leak-free. Mistakes include:
- Not pulling a deep vacuum before charging
- Undercharging or overcharging refrigerant
- Failing to use nitrogen during brazing (leading to oxidation)
- Not checking for leaks
A system with incorrect charge may not cool or heat properly, could ice up, or cause compressor failure.
Best practice is to use nitrogen purge when brazing, pull a vacuum to at least required microns (often 500 microns or less), then charge per manufacturer spec. Make your installer document superheat/subcool measurements. At Shellaby AC & Refrigeration, we won’t finalize an install without that verification.
6. Neglecting Local Codes, Permits & Inspections
Skipping permits or neglecting to meet local building or HVAC codes is a common but dangerous shortcut. This can lead to:
- Failed inspections and forced rework
- Noncompliance with energy or safety standards
- Voided warranties or insurance issues
Local jurisdictions may require venting rules, setback distances, electrical permits, or certain efficiency standards. Don’t let a contractor skip this. We ensure compliance whether for HVAC installation in Corpus Christi TX or commercial HVAC contractors in Rockport or surrounding areas.
7. Poor Indoor Air Quality & Ventilation Considerations
Some installations ignore the importance of ventilation, air filtration, and indoor air quality (IAQ). Problems include:
- Insufficient fresh air exchange
- No filter access or use of low-quality filters
- Unsealed returns that draw dust or pollutants
- Ignoring humidification or dehumidification needs
This can lead to health complaints, stuffy air, or uneven humidity. Ensure that your system is designed for ventilation and that filters are accessible and maintained. If you’re looking for air conditioning and heating service or HVAC repair services, check whether IAQ was addressed in the original installation. Shellaby AC & Refrigeration always accounts for fresh air, filtration, and proper return design.
8. Skipping Start-Up, Commissioning, and Documentation
An installation isn’t complete until it’s properly commissioned. Skipping or rushing the start-up stage results in:
- No verification of performance
- Undetected leaks or wiring faults
- No records for warranty or future troubleshooting
- Surprise failures in hot or cold seasons
A proper commissioning includes measuring airflow, temperature split, voltage, current, refrigerant pressures, and calibrating controls. Also document everything with job sheets. Contractors should provide you with operating data and system charts. At Shellaby AC & Refrigeration, we include a detailed start-up sheet for every project—residential or commercial.
Summary Table – Mistakes vs. Solutions
| Mistake | Consequence | Solution / Checkpoint |
|---|---|---|
| Wrong sizing | Inefficient cycles, poor comfort | Always request load calculation |
| Poor duct design | Air loss, imbalance | Seal, size, avoid sharp turns |
| Bad placement | Restricted airflow, false thermostat | Maintain clearance, proper thermostat location |
| Faulty wiring | Damage, safety risk | Follow code, test post-install |
| Incorrect refrigerant/ leaks | Poor performance, compressor damage | Pull vacuum, leak test, measure charge |
| Code noncompliance | Rework, invalid warranty | Obtain proper permits, follow local regs |
| Neglect IAQ | Poor air, health issues | Design ventilation, filtration upfront |
| No commissioning | Hidden faults, poor startup | Measure, document, calibrate fully |
Why These Mistakes Matter to You
You, the homeowner or facility manager, expect comfort, energy savings, and reliability. But many of these mistakes strike at exactly those goals. If you ignore them, you may face:
- Higher utility bills
- Frequent HVAC repair in Corpus Christi or elsewhere
- Early system replacement or HVAC system replacement near me
- Inconsistent indoor comfort
- Health complaints from poor air quality
- Voided warranties or insurance refusal
Understanding these pitfalls gives you power. You can ask your contractor the right questions, demand checks, and verify steps. When selecting a provider, look for one who commits to HVAC inspection and tune-up, start-up documentation, and honors warranties.
How to Choose a Quality HVAC Installer
When hiring someone—for Best HVAC Installation in Corpus Christi TX or any other location—here are things to look for:
- Proof of training, licensing, and insurance
- Willingness to perform a detailed load calculation
- Commitment to proper ductwork, airflow, and verification
- Transparent communication (show you specs, wiring plans, charge sheets)
- Documentation and checks post-installation
- Local references, reviews, and portfolio
- Will do permits, code compliance, and inspections
- Offers maintenance, emergency repair, IAQ services
We at Shellaby AC & Refrigeration embody these standards. From offering 24-hour HVAC service near me to performing tune-ups, we strive to build trust and deliver systems that perform well for decades.
Final Thoughts
Installing an HVAC system isn’t just about putting in a unit and closing it up. It’s a precise science that spans load calculations, duct design, refrigerant charging, electrical work, ventilation, and commissioning. Each of the 8 common mistakes above undermines one or more of those steps. Recognizing them helps you ensure a better, more efficient, and reliable installation.
If you’re looking for Best HVAC Installation company in Corpus Christi, or seeking service in Rockport, AC repair Corpus Christi, HVAC repair services, or heating and cooling system upgrade, reach out to Shellaby AC & Refrigeration. We know the local code, climate challenges, and performance expectations. Let us help you avoid these pitfalls from the start — for comfort, lower costs, and peace of mind. (361) 386-2886.
