Air Conditioning Basics Every Homeowner Should Understand

June 25, 2015
Ross and Witmer

If you enjoy the comfort your air conditioner provides in the sultry Charlotte and Union area summers, it’s worth taking time to learn some air conditioning basics so you can keep your system running reliably. The more you know about your A/C, the better you’ll be able to maintain it, troubleshoot as necessary and choose a new model when the time comes to upgrade.

How an Air Conditioner Cools Your Home

Air conditioning basics begin by understanding how the system actually operates. An air conditioner cools rooms by absorbing heat from inside the house and transferring that heat outdoors. It works essentially the same way as a refrigerator, with the inside of the refrigerator being comparable to the inside of your house. To accomplish this, your air conditioning system uses two main sections:

  • Indoor air handler – This unit contains the expansion valve, evaporator coil and a fan. A set of copper tubes connects the indoor unit to the outdoor unit and carries refrigerant between the two.
  • Outdoor condenser unit – This unit houses the compressor, condenser coil and a fan.

High-pressure liquid refrigerant enters the expansion valve, which releases pressure on the liquid, rapidly cooling it. The cool liquid refrigerant flows into the evaporator coils. The blower fan blows warm room air over the coil, and the refrigerant absorbs heat from the air. The resulting cool air is blown into the ducts and out to the rooms.

As the refrigerant absorbs heat, it evaporates, turning into gas form. The warm gaseous refrigerant moves through the refrigerant lines to the outdoor unit. It first enters the compressor, which raises its pressure. Then it moves to the condenser coils. A fan blows air over the coils, cooling the refrigerant inside and turning it back into a liquid. The liquid refrigerant flows through the refrigerant lines back into the house to start the cooling cycle all over again.

Why the Right Air Conditioner Capacity Matters

Cooling capacity is one of the air conditioning basics you’ll need to know to ensure your system’s performance. An air conditioner’s cooling capacity is measured in tons, but because the systems don’t weigh tons, this may seem like a strange choice of measurements. The choice is rooted in the origin of air conditioning. Before electric air conditioners existed, buildings were cooled with blocks of ice brought indoors. The ice absorbed heat from the building, melting as it did so.

A ton of ice could absorb 12,000 BTUs of heat per hour. In modern air conditioners, a ton of capacity refers to the ability to remove 12,000 BTUs of heat per hour. Most home air conditioners are between to 1.5 to 5 tons in capacity.

While you can estimate your required air conditioner capacity based on your home’s square footage, this is only a very rough guide. A responsible air conditioning technician will follow the Air Conditioning Contractor of America’s Manual J to accurately calculate your home’s exact heating load and the size of air conditioner you need.

Precision matters; an undersized air conditioner won’t provide enough cooling to keep you comfortable and will run nearly constantly, wearing out its components. Some less responsible technicians intentionally oversize air conditioners to ensure they can cool effectively even on exceptionally hot days, but this method causes more problems than it solves. An oversized system creates temperature swings, can’t dehumidify well and strains its components so they’re likely to wear out early.

Air Filters Make a Big Difference

Small and hidden away as it is, the air filter is one of those air conditioning basics that’s easy to overlook. If you want to keep your indoor air quality high and your air conditioner efficient and problem-free, however, you should be paying close attention to your filter.

A filter’s efficiency at trapping contaminant particles is shown by its minimum efficiency reporting value (MERV), with more efficient filters having higher MERVs. When choosing a filter, there are three basic efficiency groups to consider.

  • MERV 1 to 4 – Although they’re the least expensive options available, these thin fiberglass filters are meant only to protect your system from debris. They do next to nothing to improve your air quality.
  • MERV 5 to 8 – Filters in this range trap enough of the smaller dust particles, pollen and mold spores in the air to be sufficient for most homes where no one has a respiratory condition. For the best filtration in this range, look for pleated synthetic filters.
  • MERV 9 to 11 – If someone in your home has allergies, asthma or another respiratory concern, choose a filter in this range. Most filters this efficient are pleated synthetic models.

Routine Maintenance Keeps Your System Efficient

System maintenance requirements are some of the most important air conditioning basics to know. While professional annual A/C maintenance is essential, there are a few jobs you as a homeowner should perform that are just as critical. One of those is keeping the air filter clean. A dirty air filter makes it harder for the blower fan to pull in enough air. This runs up cooling bills, reduces the system’s performance and can eventually damage the fan motor.

Inspect the air filter once a month and replace it if you find a layer of dust. One-inch fiberglass filters should be replaced monthly, and while higher-efficiency filters last longer, they should still be replaced every three months, even if they look clean.

To ensure good airflow and energy efficiency, the outdoor condenser unit should also be kept clean. Check the unit now and then, and if you see leaves, grass or other debris stuck to the outside, remove the debris with a stiff brush.

At the start of the cooling system, remove the unit’s top grill and clean up dust and debris inside using a shop vac. With a gentle stream of water from a garden hose, rinse down the aluminum fins from the inside of the unit outward. When the cooling season ends, cover the unit with a sheet of plywood held down by bricks to keep out hail and other winter weather. Don’t wrap the unit up; this will hold in moisture and encourage rust.

At least once a year, check the indoor evaporator coil for dust, rust and leaks. The finest layer of dust on this component impairs its efficiency. A slightly dusty unit can be cleaned with compressed air or foaming coil cleaner. A coil with a heavy dust buildup, rust or signs of leakage should be cared for by an air conditioning technician.

Before the cooling season starts, schedule a professional A/C inspection. A technician can check the motor’s voltage and start-up amperage, tighten electrical connections, test the refrigerant charge and pressure, and take other steps that improve your system’s efficiency and longevity.

Troubleshooting an Ailing A/C

Knowing air conditioning basics also means knowing what to do if something goes wrong.

  • If your system isn’t running, first check that the thermostat is set to “cool” and for a temperature that’s lower than the room temperature. Make sure the breaker wasn’t tripped and the outdoor unit’s shutoff wasn’t accidentally switched off. A system that repeatedly trips the breaker should be professionally inspected as soon as possible.
  • If your system is producing warm or room temperature air, take a look at the air filter. A clogged air filter can impair airflow so much that the system can’t cool effectively. Putting in a clean filter should help. Check the outdoor unit, too, as a buildup of debris here can also impair airflow.
  • Banging, clanging and squealing noises usually mean a component is either loose or failing. When any unusual noises start up, shut the A/C down and call a technician.
  • If you notice a sudden drop in cooling capacity, check the copper refrigerant lines for an oily substance, which indicates a refrigerant leak. If you find signs of a leak or can’t identify another reason for the problem, call a technician immediately.

For more information on air conditioning basics every homeowner should know, check out Ross and Witmer’s home cooling solutions or call 704-392-6188.

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