Why Doesn’t My AC Cool My House Well?

By Erin Hynes | Oct. 11, 2021 7:33 am PST

Is your AC not cooling well?

Bigger isn’t always better — especially when it comes to your central air conditioner. An oversized AC unit doesn’t last as long or perform as well as a unit that’s the right size.

If you find yourself thinking the questions below, odds are good your central AC is too big for your house.

Why Are Some Rooms Still Hot When the AC Is Running?

Inconsistent cooling is typical if you have an oversized air conditioner unit. Rooms nearest the AC inside unit cool off, while more distant rooms stay warm. That’s because an oversized AC quickly cools down rooms close to the inside cooling unit. The nearby thermostat senses the cool temperature and shuts off the AC before cooled air can travel through air ducts to rooms farther away.

Why Is My House So Humid?

An air conditioner is designed to remove humidity to keep your home comfortable. The AC’s evaporator removes moisture from air as the unit cools. That moisture forms frost on the evaporator fins, and then the frost melts off the evaporator between cycles and drains out of your home.

Because an oversized AC stops running too soon, air can’t fully circulate through the evaporator for dehumidification. Your air conditioner typically needs to run for at least a half hour per cycle to circulate enough air through the evaporator to dehumidify your home.

During summer, your home feels stuffy and uncomfortable when inside air is humid. You might even see condensation on windows. Mold and mildew might form quickly in the bathrooms; and because mold and mildew can cause respiratory problems, you might cough and feel congested if you suffer from mold allergies.

Additionally, the brief interval between short cycles prevents frost from melting and draining out of your home. The evaporator is less efficient at dehumidifying your home when the defrost/drain process isn’t completed between frequent, short-cycling cooling cycles.

Why Is My Electric Bill so High?

Motors in the AC unit require extra power to start. Short cycling of an oversized AC unit causes the compressor and fan motors to use excessive starting current — driving up your electric bill. Additionally, an oversized unit uses a larger compressor, so it consumes more power than a right-size AC unit.

You can easily see your electric bill skyrocket in the summer even though your home doesn’t feel very cool.

Why Does My AC Unit Turn On and Off a Lot?

When an AC runs for 5 or 10 minutes and then shuts off, and then runs again in 5 or 10 minutes, it’s called short cycling. An oversized unit repeats the on/off cycle in 15 to 20 minute intervals; an AC that is the right size runs for at least 30 minutes before shutting off.

An oversized AC system short cycles because the unit quickly cools the air in the space surrounding the inside cooling unit and thermostat. After only a short time, the thermostat senses the cooler temperature and shuts the AC off.

Short cycling is the underlying cause of oversized AC problems such as inconsistent cooling, high humidity, high electric bills and high repair bills.

Why Does My AC Keep Breaking Down?

Short cycling puts more wear and tear on the compressor and fans of your AC. Their motors run hotter when they have to start frequently. Also, they don’t have a chance to cool down fully between short cycles. Excessive wear causes more breakdowns.

Electric components such as motor capacitors can also wear out quickly due to short cycling. Capacitors are electrical devices that help provide extra electrical current to the compressor and fan motors during AC start-up. Excessive use of the capacitors during short cycling wears them out faster.

How Do I Fix This AC Problem?

Replace your oversized AC unit with a right size air conditioner.

Schedule a free visit with a Sears Home Services HVAC consultant to examine your current AC system and recommend the right size central air conditioner in your home.

The consultant will identify a unit that will efficiently cool and dehumidify your home. The investment in a right size central AC unit will pay for itself with lower electric bills and repair bills over time.

To top it off, you’ll be much more comfortable in your home with the right-sized AC.

Get a free in-home consultation

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