Did I Receive an Improper HVAC Installation?

C.E. Larusso
Written by C.E. Larusso
Updated January 20, 2022
A young man under a blanket working on his laptop
Photo: Marcel ter Bekke / Moment / Getty Images


  • An HVAC system must be properly installed for your air conditioner and furnace or heat pump to keep your home comfortable.

  • More than half of the HVAC systems in American homes are poorly installed.

  • Signs of faulty installation include high energy bills, electrical issues, inadequate airflow, and leakage.

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Whether you’re shivering in the frozen depths of winter or wilting in the summer sun, a reliable HVAC system is a blessing to your family’s comfort. However, if the system isn’t correctly installed, you’re likely paying more money for fewer benefits. If you live in the U.S., the odds are that some of your HVAC components aren’t operating at total capacity. According to ENERGY STAR, more than half of the HVAC systems in American homes aren’t delivering the efficiency and savings they’re capable of due to installation errors. 

Read on to discover the symptoms of an improperly installed HVAC system, common installation errors, and how you can avoid this fate.

Symptoms of Improper Installation 

Some of the signs are unmistakable: 

  • Leaking water (around the indoor air handler or the outdoor unit)

  • Blown fuses and other electrical issues 

  • Indoor temperatures falling far from the mark set by the thermostat 

  • Poor airflow

  • Excessive noise from the HVAC unit (a low rumbling and clanging or a high-pitched whistling sound)

  • Hot and cold spots throughout the house

If you’re having these kinds of problems with the new HVAC system, the conclusion is obvious: Something went awry during installation. 

In many cases, improper installation results in hot or cool air escaping through the ductwork and getting trapped between walls or in a crawl space. This can drive up your bills and waste precious resources while you languish in suboptimal temperatures. According to ENERGY STAR, the correct installation of your HVAC components can result in up to 36% in savings on air conditioner or heat pump usage and as much as 18% for a furnace.

Common Installation Mistakes

When an HVAC system is performing less efficiently than it should, it may be due to one of these installation errors. 

1. Poor Drainage

Your air conditioning unit generates a lot of moisture, which condenses around the coils to produce cool air for your home. Proper drainage mechanisms are essential to avoid leakage around in the unit or from its components and to ensure water isn’t pooling and fostering the growth of mold and mildew. If you see leaks or notice unpleasant odors, it could be an issue with the secondary drip pan, the condenser pan, or another part of the unit’s drainage system. 

2. Faulty Ductwork

Undersized ducts and ones that have been kinked or disconnected will restrict the airflow, distributing the pressure unevenly and resulting in hot and cold spots throughout the home. Loose screws or brackets can also create unpleasant noises when the system is operating. 

Suppose the previous contractor cut corners on the ductwork, using cheap materials or leaving gaps and cracks sealed only with tape. That quick fix will soon fail, radically compromising your system’s efficiency. Whenever you hire someone to install a new HVAC system, make sure they replace any old ductwork in the house since they have likely suffered some damage over the years. 

3. Electrical Problems

Connecting the HVAC units to your home’s electrical system is one of the trickiest parts of the job and often the place where things go wrong. HVAC systems often rumble and shake as they operate, putting a strain on the wiring, which can quickly come loose if they weren’t secured correctly during installation. 

An inexperienced technician or DIYer in over their head may also install an incorrectly sized fuse. The system may work OK at first, but it’ll quickly lead to blowouts and poor performance if not replaced with the proper part. 

4. Inappropriate Sizing 

The power of an HVAC unit correlates with its size—the larger a unit, the more hot or cold air it can produce—but bigger isn’t always better. Installing a unit that’s too large for your home can lead to constant start and stop errors, and a unit too small will quickly wear out. 

Factors such as local climate, the house orientation, the materials that compose it, and the height of your ceilings can affect the load size that’ll most efficiently treat your home. A good installation technician will make the complex calculations necessary to determine the right size for your home rather than relying on loose rules of thumb. 

5. Bad Venting

While many HVAC installation mistakes can lead to wasted money and discomfort, a poorly vented gas furnace unit can quickly pose threats to the health and safety of your family. The furnace produces toxic gases (including carbon monoxide) as part of its regular operation, and if the system isn’t adequately vented, they’ll feed into your home. 

There are a few different ways an inexperienced or cost-cutting technician might fail to properly vent your unit, including:

  • Installing pipes that are the wrong size

  • Using the wrong materials

  • Neglecting to install a fresh air uptake vent

  • Placing the vent pipes in an area where they might get buried in snow or knocked out of place by high winds 

6. Poor Placement

Where you install your HVAC system and its components has implications for its performance. A replacement system should never be placed in the same spot as the old unit. You should also shield the system from direct sunlight so the warm rays don’t overburden the system. 

The placement of the thermostat is also significant: If it’s located near windows or heat sources, it won’t accurately measure the temperature inside. Additionally, the outdoor condenser unit must have adequate clearance, at least 2 feet around the whole perimeter, to ensure efficient operation.

Hire a Reputable Pro to Avoid Installation Errors

If you’re thinking about saving money on your new HVAC system by handling the installation yourself, think again. HVAC installation is a high-risk job with high-stakes consequences if performed incorrectly—potentially even imperiling the lives of you and your family. In most cases, DIY installation is also likely illegal, with states requiring licensure for anyone handling the refrigerant required by a central AC. 

Whether you’re adding a brand-new system to your home or replacing an old setup, hire a professional HVAC contractor in your area. Ask if their technicians maintain certifications from the North American Technician Excellence (NATE) or Mechanical Service Contractors of America (MSCA) and whether they follow ENERGY STAR’s quality installation guidelines

Be suspicious of contractors offering unusually low bids. Repairing a poorly done installation will be significantly more expensive than paying more to ensure it’s done correctly the first time. In a typical home, the HVAC system accounts for about half of the monthly energy bill, so spending a little more money to hire quality technicians for the installation and inspections is an investment you’ll quickly recoup.

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