Types of AC Coils: Choosing the Right Ones for Your Cooling System

Air conditioning systems have to be matched to your needs to keep up with the demands of cooling your home during the hot summer months. No matter how durable your system – and how well you maintain it – the individual components may need repairs or replacement along the way.

When you work with professional, experienced AC technicians like those at Bell Brothers, you can count on AC repair and replacement parts that are a perfect match for your current system to get it running like new. We’ve been providing homeowners with on-time service, upfront pricing, and friendly, knowledgeable technicians for over 30 years.

Here’s everything you need to know about your AC coils, the different types, and how you can ensure that you’re getting the right match for consistent, energy-efficient cooling.

Air Conditioner Coils

Air conditioner coils are an important part of the air conditioner’s function. They are responsible for removing the heat and humidity from your home and transferring it outside.

No matter the type, air conditioners operate on the same principle – providing cool air by removing heat and humidity. Standard ACs have specialized chemicals and refrigerants with three primary components: a compressor, condenser coil, and evaporator coil. Combined, these components create a process to convert refrigerant from a liquid to a gas, and back, to facilitate cooling.

Here’s a breakdown of the types of AC coils:

Condenser Coil

The condenser coil is housed within the condenser, which is outside of the home. There are several components, including a compressor, a fan, and fins, as well as the condenser coils.

When the refrigerant absorbs heat from your home, it travels through copper tubing to the condenser unit. This low-pressure, warm refrigerant gas goes into the compressor, where it’s then pressurized and turned into a hot, high-pressure gas.

This gas travels from the compressor to the condenser coils. A fan blows the warm air over the condenser coils, then the cooled refrigerant draws the heat from the gas. There are several condenser coils to expose more of the refrigerant to the fan and remove as much heat as possible.

The refrigerant changes from a hot gas to a hot liquid as the refrigerant cools. Once cooled, it can travel back through the copper tubing into the expansion valve in the indoor unit to be distributed through your home. The process begins anew to continue cooling your hot indoor air.

Evaporator Coils


Evaporator coils are tubing in a circular “coiled” form. They’re found inside your air handler. Evaporator coils are made of metals that conduct heat easily, such as steel, copper, and aluminum.

The evaporator coils house refrigerant, which is cooled using a cooling mechanism and enclosed in panels that are positioned in the shape of an “A.” They also have thin pieces of metal, “fins,” that draw air in to be cooled near the coil refrigerant.

The indoor unit takes in the warm air, which enters through the expansion valve. This valve releases pressure from the liquid refrigerant to cool it and controls how much refrigerant flows into the evaporator. The refrigerant leaving the expansion valve is then cold, so it can absorb heat from the air. The warm air then passes over the low-pressure, cooled liquid refrigerant to cool it.

When water vapor from the indoors reaches the evaporator coils and refrigerants, it condenses into a liquid. This liquid is then drained into the condensate pan and travels outside. The evaporator coil is essential for reducing humidity.

How to Choose the Right Coils for Your AC

An air conditioner’s cooling capacity is measured in tons or British Thermal Units (BTUs) per hour. In new systems, the evaporator coil and the condenser coil have the same capacity rating. When it comes time to replace a coil, unfortunately, many homeowners mistakenly believe that they improve their system’s performance by installing a coil that has a higher capacity rating.

For example, they may upgrade from a 4-ton to 5-ton condenser coil, thinking that this will improve the cooling capacity. Mismatching coils like this can put additional strain on the other components, however, leading them to break down sooner.

In addition, the whole system may not operate efficiently. Minor cooling demands, such as during the transitional seasons of fall and spring, require the AC to work much harder and use more energy to produce minimal cooling. The result is low home comfort, high energy bills, and a reduced lifespan for the AC.

Many manufacturers state the coils’ capacity and SEER ratings for replacement and specify that any replacement coils must match. If you neglect to match your coils, you may void your warranty.

Here are some other aspects to consider:

  • Size: The evaporator and condenser coils should match the capacity of your HVAC system. Undersized coils may not provide enough cooling, but oversized coils can increase energy costs. The one exception is higher efficiency systems, which may require a coil with a capacity that’s higher than the desired output (this will be noted in the manufacturer’s guidelines).
  • Capacity: AC coils are advertised as being matched to a specific size unit in tons or BTUs/hr. One ton of cooling is about 12,000 BTUs/hr. The one exception is higher efficiency systems, which may require a coil with a capacity that’s higher than the desired output (this will be noted in the manufacturer’s guidelines).
  • Compatibility: The coil should always be appropriately sized to fit in the space allotted within your unit. Evaporator coils are usually sold in corresponding widths to the 4 standard widths for AC systems. They should match as closely as possible, but if an exact match isn’t available, smaller is better.
  • Coil type: Evaporator coils come in slab coils and “A” coils. Slab coils have a simple slab of fins with tube coils to carry refrigerant, which are used in systems that require low airflow resistance. “A” coils consist of two slabs of fins arranged in an “A” shape, which allows them to have similar surface area to a slab coil, but they can be installed in the system with no transitional ducting.
  • Coil orientation: Slab coils are only suitable for installation in horizontal configurations, whereas A coils are available for both horizontal and vertical configurations. It’s important to use the coil with the proper orientation to ensure water drains properly. Otherwise, you could end up with mold growth or poor operation.

Signs Your AC Coils Need Replacement


The evaporator coil and condenser coil are essential to your home’s AC system. Without either one, your AC can’t cool your home properly and remove humidity, so they should be repaired or replaced as soon as there are problems.

Here are some signs that your AC coils may need to be replaced:

  • Water leaks: If you notice a lot of water leaking from your AC unit, the evaporator coil could be damaged. As coils age, their interior lining can erode, causing water leaks. Frost on the coils can also cause a leak, as they flood the condensate line after it thaws.
  • Warm air: Because evaporator coils pull humidity from the air, a damaged evaporator coil can make your AC blow warm air. Without the coil working properly, your system can’t remove humidity properly. This can also damage your compressor or other components.
  • Airflow issues: If your AC has poor airflow, it could be due to clogged vents or broken fans in your condenser coil.
  • High energy bills: You may notice high energy bills if your coils are dirty or damaged, but there are many possible reasons for poor energy efficiency.
  • Corroded lines: Corrosion or damage in your coils can cause them to work less efficiently. This is often caused by continuous freezing and thawing or chemical sprays that interact with your evaporator coil. You can spot corrosion if your drain pan or coil surface has oil on it.
  • Strange noises: Odd noises coming from your AC are always a sign to watch for. With coils, you may hear banging, clanging, or hissing if there’s damage like a refrigerant leak or debris. Always have this checked out by an AC technician.
  • Dirty coils: If you don’t clean your coils consistently, they may break down earlier. Dirt and debris build up on the coil, preventing proper airflow, but eventually the buildup will become embedded in the coil and harder to remove. These coils will need to be replaced.

Be Proactive with AC Maintenance

When it comes to your AC, a proactive approach is much better than waiting for something to go wrong. Regular AC maintenance from a qualified AC technician involves an inspection and tune-up of your AC’s operation and components, including your coils, to spot problems early.

In addition to saving you a lot in potential repairs in the future, AC maintenance ensures that your AC runs at its best for optimal home cooling. You enjoy a cool, comfortable home with better energy efficiency, fewer repairs, and a longer lifespan for your AC and its components.

Need Help with Your AC Coils?

Whether you need replacement AC coils or there are problems that need repairs, Bell Brothers can help. Contact us today to schedule your appointment!