Evaporator Coil & Air Handler Buying Guide

Evaporator coils and the refrigerant that flows through them are the veins and lifeblood of your air conditioning system. They come in a couple of different configurations which you should know about.

What is An Evaporator Coil

In an air conditioning system, an evaporator coil is a series of tubes containing cold refrigerant that absorbs and transfers heat out of your home. It is installed in one of two ways:

• If you have an existing furnace that heats your home in the winter, the evaporator coil is a separate component that uses the blower inside your furnace to distribute cool air. 
• If you don't have an existing furnace, you need to purchase an indoor air handler, which contains a blower and evaporator coil in one unit.

In both cases, the indoor evaporator coil works with an outdoor unit that releases the heat.

Coils can also be used in heat pump systems, where the process is reversed. In that case, an evaporator coil in the outdoor unit absorbs heat from the outside and transfers it inside, releasing it via the blower.

Coil Capacity

Coils and air handlers are often advertised as being for a specific size unit. This is often represented in terms of Tons or BTU per hour.

Both are common measures of cooling capacity and are used interchangeably (1 Ton cooling = 12,000 BTU/hr). These capacity ratings may be accurate for basic installations, but higher-efficiency systems often require a coil with a listed capacity higher than the desired output.

Manufacturers specify the appropriate coils for these applications, and we will be happy to help you select the correct components for your system.

Coil Width

Furnaces typically come in four standard widths, and evaporator coils are sold in corresponding widths to simplify installation. Width should be selected to match the furnace as closely as possible, and it has little to no effect on operating performance or efficiency.

Coil Types: Slab Coil vs A Coil Vs N Coil

Coils are available in three main types: Slab coils,  A-coils, and N-coils.

Slab coils

As their name implies, slab coils consist of a simple slab of fins with tube coils to carry refrigerant. They are primarily used in systems that require very low airflow resistance.

Slab coils are often larger than the furnaces they are used with, so it is critical that the installer build a transition to ensure proper airflow and operation.

A-coils

A-coils consist of two slabs of fins arranged in an A-shape formation. This allows them to have a total surface area similar to that of a slab coil, but install directly onto the furnace with no transition ducting.

N-coils

An N-coil is a derivation of an A-coil that uses three fin slabs arranged in an N-formation. It is designed to fit on a furnace directly like the A-coil but has a shorter overall height.

Coil Orientation

While slab coils are only suitable for installation in horizontal applications (i.e., applications where the airflow is horizontal through the coil), "A" and "N" coils are available for both horizontal and vertical applications. A coil with the proper orientation must be used, or water will not drain properly, which can cause mold growth, poor operation, or property damage.

Air Handler Blower

Air handlers are available with a number of blower options that offer various combinations of cost, comfort, and efficiency. Detailed information about these options can be found in the blower section of our furnace buying guide.