When it comes to a new air conditioning installation, proper sizing is as important as the quality of the unit. A right-sized system will provide your entire home with steady, reliable and consistent cooling all year long. The better the sizing, the more efficient the unit and the more comfortable you’ll feel.
Homeowners with oversized or undersized air conditioners might get plenty of cold air, but that air might feel like a recurring Arctic blast that makes you reach for a sweater. That is not proper cooling. You should feel refreshingly cool in your home, not like you’re living in the freezer.
AC System Is Too Small
An undersized air conditioner will spend its entire service life trying to supply your home with enough cool air to keep you comfortable, but it will never be enough. Nevertheless, the too-small air conditioner will die trying.
Common symptoms of an undersized system include constant cycling off and on. It doesn’t have enough bandwidth to complete a full cycle, so the too-small air conditioner shuts off, takes a rest and tries again. It’s quite sad when you think about it.
Indoor temperatures are never cool enough. You might have periodic infusions of icy air or hot spots where the cold air doesn’t reach. The air is typically humid, stagnant, stuffy and poorly ventilated.
AC System Is Too Large
A cooling system that’s too large is just as bad as one that’s too small. Overly large systems cycle on and off just like too-small units, but they do so for other reasons.
Unlike a too-small air conditioner, a too-large system has plenty of power to cool a house. But in this case, the problem is too much power instead of too little.
When an air conditioner is too big for its britches, it tries to cool your home very quickly. That might sound good, but it’s not.
The system will turn on and off continually throughout the day, a scenario known as “short cycling.” That’s bad because the system needs to run for longer cycles in order to remove enough humidity and heat to keep you comfortable.
When the too-large air conditioner cycles on, it will blast the house with ice-cold air and turn off. The blast of cold air quickly dissipates, and as it does, the unit cycles on again to deliver another short shot of freezing air. The unit spends its life repeating the same behavior, and it never solves the problem.
What Affects the Sizing of an Air Conditioner?
Proper AC sizing is a skill that not all HVAC contractors have mastered. In many cases, a contractor will simply replace an old air conditioner with a new and upgraded version of the unit you already have.
This approach almost always fails, even if the existing unit was right-sized when originally installed.
The planet is in constant motion, and every environmental shift affects air conditioner performance and efficiency. A new AC installation typically requires at least minimal sizing adjustments, even if nothing else changes.
The type, brand and rating of your new system will impact the sizing, as will its square footage and BTUh rating. Sizing and performance are affected by the quality of insulation and the condition of your ductwork.
Sun exposure, shade trees, ceiling height, construction materials and heat-generating appliances all play a role in the sizing process. Ceiling height and fireplaces have an effect, as do construction materials such as stone, brick and wood.
How to Ensure Correct AC Sizing
The Manual J calculation factors in a great many of the markers already discussed above, and the results offer a very accurate measure of the AC sizing requirements for your home.
For homeowners seeking maximum value from a new AC investment, a home energy audit that includes a Manual J load calculation will determine the exact sizing needed for state-of-the-art indoor comfort and substantial energy savings.
Many AC systems fail to achieve even average equipment performance, and poor sizing is usually to blame. A Manual J load calculation is the only way to determine which size is the right size.
What Is the ACCA Manual J Load Calculation?
When it comes to determining the correct size of a cooling system, the Manual J load calculation is the gold standard. It was developed by the Air Conditioning Contractors of America (ACCA) to be the most accurate measure for determining the size of a cooling system.
It shows how much cool air your AC needs to add to your home in any given summer to attain optimal performance levels and maximum indoor comfort. Baseline is attained when an AC can cool your home to 75 degrees in peak summer heat.
This formula often reveals that you require a smaller air conditioner than the one you have now.
To learn more about maximizing the return on your Birmingham, AL, AC installation, visit One Hour Air Conditioning & Heating.