Evaporator Coil Explained: A-Coil, N and Z-Coil (All Explained With Pros and Cons)

Evaporator Coil Explained

Nothing makes the winter cold more bearable than the good old heat pump, and nothing can beat the heat better than an air conditioner to come to your aid during the harshest months of the year.

Yes, these heating and cooling systems can be extremely resourceful in times of need, and make life ten times easier and more comfortable. 

While we may not always be well informed about what exactly goes on inside these units, we know enough to know that they reason out the temperatures and make our bodies feel better by introducing a cool breeze during the first half of the year and producing warmth in the other.

However, it is quite simple in hindsight. The principle of most such heating and cooling systems is air exchange. The room temperature air is pulled in, and freshly cooled or heated air replaces it.

The first part of the process is the most important of all, and it is executed by your heating/cooling unit’s evaporator coils.

Today, we discuss the significance of evaporator coils and highlight some major evaporator coil types.

How Does The Evaporator Coil Work?

The main role of an evaporator coil is in taking in heat or moisture from the air that is already circulating in a room. By doing this, it makes the cooling process simpler and faster.

A refrigerant liquid that flows through the coils of your system acts as the medium through which heat is absorbed and transported to and from until the cool or hot air required is blown into the room.

This same process is repeated a couple of times until the temperature of the room is brought down to the temperature set on the thermostat.

Now, it really does sound like the refrigerant is doing all the work, but the evaporator coil works in the shadow. The refrigerant flows inside the evaporator coils, which are typically built of copper or steel.

These materials are known to conduct heat, and thus, any heat flowing in the refrigerant liquid is attracted by the coil. Keep in mind that the evaporator works hand in hand with the condenser to complete this process.

Different parts of the evaporator coil contribute to the success of this process. They are:

Radiator fins, which support energy transfer by maximizing the surface area and temperature. All types of evaporator coils usually harbor a radiator-style fin.

The Tubing, which is made of steel, copper, or aluminum not only acts as a middleman between the indoor and outdoor coil but is also a conducting material of heat.

Refrigerant, stimulated by the compressor towards the evaporator coils. Depending on the setting, the refrigerant takes in indoor heat from the room (for cooling), or outdoor heat (for heating).

Sloped or Slanted Design, which ensures that any condensate or moisture resulting from the process is expelled outside through the drain pan. Thanks to the slanted design, there is little chance of any moisture lingering and causing adverse effects like freezing the coils or causing the growth of bacterial material.

Typically, you will find the evaporator coil attached to your heat pump, or fixed inside your air conditioning system in the indoor unit.  It is not entirely safe to handle any evaporator coil issues without the help of an HVAC technician.

To completely round up the heating/cooling process, the evaporator coil is supplemented with help from the condenser coils.

While the evaporator coil absorbs heat, the condenser coil allows for the refrigerant to let out the heat is absorbed from your home. The condenser coils, thus, can be attributed to the release of heat. 

The size of your evaporator coils also matters as it is important that it is simultaneous to the capacity supported by your HVAC heating or cooling system. You can find evaporators ranging from 1 ton to 5-ton sizes on the market. 

While there are many other features that are being integrated into evaporator coils by manufacturers today, coil shapes play a predominant role in determining the performance of an evaporator coil in your unit.

What Is A-Coil?

The A-coil is considered to be the standard coil design in the industry. Many popular manufacturers today- names like Trane, Goodman, and Carrier- have produced excellent units with these coils.

The A-shaped coil is designed in such a way as to protect the coil fins from being exposed to moisture. Its design, which has a pair of slanted coils meeting at the top, ensures that water runs right into the drain pan. 

The interior of the coil also allows for air to travel through it and exit from the sides. One of the remarkable things about this model is that it has a large surface area to account for efficient heat exchange.

The A-coil also has a big reputation, so it is likely more easily found than other coil types. Any hardware store you go to will recognize the famous A-shaped coil immediately.

N and Z Shaped Coils

N or Z-shaped coils are not much different. Both embody the similar zigzag pattern of their letters, and both embody the difference in their positioning of them as well.

That is, with the N-shaped coil positioned vertically and the Z-shaped one taking a horizontal narrative. These are called zigzag coils. No one has found them particularly variable in terms of their working. 

When compared to A-shaped coils, however, they are considered to be more efficient thanks to a third radiator fin that lends them some additional surface area to work with. This increases their tendency to absorb heat and release it.

These coil types are equally as popular as A-shaped coils. However, what puts them slightly behind is that they are not entirely accessible and hence cannot be maintained or cleaned very well. As a result, this can have consequences on the AC/heat pump performance.

Slab Coils

Slab coils are not very widely used compared to the previous models. The design makes use of a slab of finds with coils running in between. These are not gifted with high capacity and generally work better with units that need low airflow resistance.

Which Evaporator Coil is Better?

Now arises the question- which evaporator coil is the best? Coil designs can really affect the process of heat exchange, so it is important to choose carefully.

With A-shaped Coils, you can be guaranteed that it will support the amount of refrigerant required by your AC to function at a good efficiency rate.

However, with a much larger surface area, N-shaped coils can be credited for being able to run an ever-larger flow of refrigerant while remaining small and compact. 

N-shaped Coils are also more advantageous because of their extra leg of fins, as well as the better quality of design that can be attributed to their composition of tubing materials.

N-shaped coils can also make use of a ‘thermal expansion valve’ which assesses the rate of refrigerant required by the coil and helps make the process more accurate.

Slab coils don’t have the most boast-worthy efficiency in performance, but they can be credited for their simple design, which makes careful use of space.

Things to Consider Before Choosing an Evaporator Coil

Evaporator coils are a whole niche of their own. While you may not have paid much attention to them at first, there might come a day where there is a need to replace them. Some basic aspects to keep in mind in their regard are:


Your Evaporator coil must coincide with the size or BTU of your AC/furnace. Coils have size units of their own, and these are expressed in tons or BTUs. 1 ton is symbolic of 12,000 BTUs.

You must select the coil that appropriately matches your system’s needs. However, some manufacturers may list that the capacity of the coil needs to be higher than that of the unit. Clear instruction will be provided in your unit’s manual. So make sure to check it before purchasing.


There are 4 basic width sizes in the market for evaporator coils. You must choose the size that facilitates easy installation and set-up.


The airflow types must also be kept in mind, as the whole set-up can go haywire with a mismatch in the unit’s and the coil’s airflow. If your unit’s coils are prescribed to have a vertical airflow, invest in N-shaped or A-shaped coils.

Slab coils work horizontally, but you can also find N-shaped (Z coils) and A-shaped alternatives that support horizontal airflow.

Coil Type

Finally, the coil type matters. Between A, N, and Z, and Slab coils, there are many advantages and disadvantages to all. The elaborate discussion of different coil shapes above should allow you to decide which suits your unit best.


Your evaporator coils form a crucial part of your heating or cooling system. You can show your appreciation for them by maintaining them regularly.

Clean coils encourage your AC/furnace’s efficiency, while dirty ones only improve your electricity bills- they can also be hazardous to the other components of your unit. Changing the air filter also slows down the wear and tear of the coils.

Additionally, HVAC pros are always one call away to perform a thorough clean through on the inside of your heating or cooling unit. 

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