10 HVAC Installation & Maintenance Mistakes That Hurt Performance

Every homeowner wants an HVAC system that performs well throughout the year and doesn’t drive up energy costs. However, some HVAC technicians make mistakes that hurt or limit the systems they install.

Correct Installation Is Critical for HVAC Performance

A National Institute of Standards and Technology survey concluded that even if customers purchase the most energy-efficient heat pump, air conditioner, and furnace, they’ll go to waste with a subpar installation.

The takeaway? Don’t purchase the very best HVAC equipment and have it installed on the cheap. The installer is as critical as the equipment you buy.

Improper installation can increase household energy consumption by as much as 30%. This is reason enough to call an experienced HVAC service like West Coast Chief!

Here are 10 of the most common HVAC installation mistakes:

1. An Oversized HVAC System

• The HVAC service provider might install a system too powerful for your house.
• Perhaps they rushed the job and took incorrect measurements.
• The technician could be inexperienced or even greedy. Bigger system components pad the bottom line of the seller.

But an oversized system will heat or cool a house fast and shut down fast. A system that stops and starts frequently will use far more energy than a system that runs continuously at lower power. It will also do an inferior job of maintaining a comfortable temperature.

2. An Undersized HVAC System

On the other hand, an HVAC technician might install a system that doesn’t have enough heating or cooling capacity for your home.

Some contractors do this to save on installation costs, since smaller systems are less expensive. But it’s a false economy because an undersized system will run all the time and rack up huge energy bills. It will also wear out faster than a properly sized system.

3. Improperly Sized Ductwork

If the ducts that carry air to and from your HVAC system are too small, then the system has to work harder, use more energy, and won’t cool or heat your home as effectively.

On the other hand, if the ducts are too large, the HVAC system will cycle on and off too frequently, wasting energy and causing premature wear and tear. Either way, you’ll be paying more in energy bills than you should.

4. Poorly Sealed Ductwork

Leaky ductwork allows outside into the ducts, which raises or lowers the temperature of the air passing through and makes your HVAC system work harder than necessary. It can also let humid outside air into your home, leading to condensation and mold growth.

Up to 30% of your heating or cooling is lost through incorrectly sized or leaky ductwork. This means higher energy bills for you and reduced comfort in your home.

For a heating and cooling system to perform at its best, it must have good airflow. Inexperienced HVAC services might sometimes overlook this factor; the oversight will ultimately cost you.

5. Incorrect Refrigerant Charge

If your air conditioner has the wrong refrigerant charge, it won’t work as efficiently. Your home won’t cool as it should, and you’ll see an unwelcome spike in your energy bills.

In some cases, an incorrect refrigerant charge can make your air conditioner freeze up, leading to more expensive repairs.

This brings us to our next point… Hire someone to maintain your HVAC system.

6. Lack of Maintenance

Your HVAC system needs regular maintenance to function at its best.

• Filters should be changed regularly.
• Coils should be cleaned.
• The ductwork should be checked for leaks.
• The entire system should be inspected periodically and tuned to keep it in peak operating condition.

7. Poorly Insulated Attic; Leaky Walls, Doors & Windows

An attic without good insulation allows heat to escape during the winter, and cold air to enter during the summer. The same goes for leaky walls, doors, and windows.

Leaks force your HVAC system to work harder than it should, wasting energy and money. They also make your home uncomfortable, as anyone who has sat in a draft will attest.

8. Faulty Electrical Wiring & Switches

Defective electrical wiring can cause all kinds of problems.

Your HVAC system might not start at all.

It might run inefficiently, overheat, and break down prematurely.

In some cases, faulty wiring can be a fire hazard. Fixing the wiring is not a do-it-yourself job. You’ll need a qualified electrician.

9. Exhaust Fans Not Vented to the Outside

Bathroom and kitchen exhaust fans should vent to the outside. If not, humid air in your home could contribute to mold growth, and your HVAC system will work overtime to remove the extra moisture from the air.

You can avoid the problem by hiring a qualified HVAC contractor for your installation or maintenance needs.

10. Forgetting the “V” in HVAC

New homes are tighter than ever, almost hermetically sealed. New energy codes require better sealing and sometimes blower door tests to verify air tightness.

The upshot is that new homes need good mechanical ventilation, especially in kitchens and bathrooms.

Be sure that the company you choose for HVAC services measures the airflow in your ventilation systems according to three mechanical ventilation principles:

• Positive pressure
• Negative pressure
• Balance

You don’t have to understand what these principles mean, but your HVAC service should.

Call West Coast Chief for Your HVAC Needs

At Chief, we’re experts at installing and maintaining HVAC systems, from ductless mini-splits to central air conditioners.

We’ll ensure your system is the right size for your home, properly installed, and regularly maintained.

We’ll also check for other problem areas, like poor insulation and ventilation, and make recommendations to solve them.

This way, you can ensure your HVAC system provides the maximum comfort and energy savings for you and your family.

To learn more or schedule a free consultation, call us today.

Q: What’s the most common mistake that affects HVAC performance?

Neglecting to change the air filter regularly is one of the most common and damaging mistakes. A dirty filter restricts airflow, makes your system work harder, reduces efficiency, and can lead to system breakdowns. Filters should be checked monthly and replaced every 1–3 months.

Q: How does blocking vents affect my HVAC system?

Closing or blocking vents in unused rooms may seem like a way to save energy, but it can actually increase pressure in the system. This forces your HVAC unit to work harder, potentially leading to duct leaks, reduced efficiency, and long-term damage.

Q: Can skipping HVAC maintenance really cause problems?

Skipping annual professional maintenance increases the risk of breakdowns, reduces system lifespan, and causes minor issues to escalate. Preventive maintenance includes cleaning, inspecting key components, and identifying problems before they become costly repairs.

Q: Is it bad to set the thermostat too high or too low?

Extreme temperature settings don’t cool or heat your home faster — they just make your HVAC system run longer, increasing energy use and wear. It’s better to use moderate, energy-efficient settings or a programmable thermostat to maintain comfort and control costs.

Q: Why is poor insulation a problem for HVAC performance?

Without proper insulation, your HVAC system must work harder to compensate for lost heat in winter or cool air in summer. This not only increases your energy bill, but also strains the system and shortens its lifespan.

Q: Does furniture placement affect HVAC efficiency?

Placing furniture or curtains over vents or returns can block airflow, which reduces system efficiency and creates hot or cold spots in your home. Ensure vents and intakes are free from obstructions for even airflow.

Q: What are signs that my HVAC system is being overworked?

Signs include unusually high energy bills, uneven heating or cooling, excessive cycling (turning on and off), strange noises, or reduced airflow. These symptoms often result from clogged filters, blocked vents, or lack of maintenance.

Q: How can I improve my HVAC system’s performance and extend its life?

Change air filters regularly, schedule yearly professional tune-ups, keep vents unblocked, insulate your home properly, and use a programmable thermostat. Small steps like these can keep your HVAC system running efficiently and reliably for years.