What Makes a Coil Custom?

Colby Maun • June 22, 2026

What exactly makes a custom coil custom? Most facility managers assume that a custom coil only differs from OEM in sizing. The reality is that dimensions are only a fraction of what makes a custom coil custom. Each job is different, with many different factors going into a custom coil, such as dimensions, tube configuration, fin design, materials, and performance requirements.


The most commonly thought of aspect when it comes to custom coils is the dimensions. This includes height, width, and depth of the coil, which allows for custom replacement coils to fit perfectly into the system they are designed for. Doing this without major modifications is crucial when manufacturing a custom replacement coil.


The tube configuration of the coil also plays a very important role in customization. The circuitry, number of rows, and tube diameter all impact this aspect and contribute to the efficiency and heat transfer of a custom coil. 

Fin design affects the airflow and heat transfer efficiency of a custom coil, which is very specific for each job. Fin types can be straight, corrugated, louvered, or ripple. A straight fin type is the simplest design and is easier to clean, which makes it more suited for industrial environments and dirty facilities. Corrugated fins are wavy in pattern and transfer heat better than straight fins, making them good for rooftop units and air handlers. Louvered fins contain small, angled cuts and work best in high-performance and energy-efficient systems. The specific spacing of the fins matters as well, since each job contains different airflow and pressure drop requirements.


Another factor that must be taken into account for a custom coil is the material the coil is manufactured with. Custom coils can be made with copper, galvanized steel, stainless steel, aluminum, cupronickel, and more. Copper is traditionally the industry standard for tubing; however, it can also be found rarely in the fins. Copper transfers heat very efficiently and is very easy to repair, but this comes with higher costs and corrosion concerns. Galvanized steel is most common in the case of the coil, since it is durable and affordable, yet it faces shorter lifespans in harsh environments. Stainless steel is an option for tubing, fins, and casing, and is commonly selected for its durability and corrosion-resistant nature. It’s often one of the more expensive options and does not transfer heat as well as other materials. Aluminum is the most common material for the fins in a coil and is often chosen for its inexpensive and lightweight properties. For fin purposes, it is ideal, yet for tubing and casing purposes, it can be more difficult to repair and more susceptible to physical damage. Cupronickel is only used for the tubes and is the premium corrosion-resistant option. It is very expensive, which puts it behind copper in terms of commonality. 

The final factor that goes into a custom coil is the performance requirements that each job entails. Pressure drop, operating temperatures, capacity, and airflow all differ based on the requirements of the job. When it comes to performance requirements, flow rate is one of the most important elements. Flow rate is the volume of air or fluid moving through the coil, and having a flow rate that is too high or too low results in inefficiency and lower coil performance. Which type of refrigerant the coil uses impacts customization since different refrigerants behave differently. With the new refrigerant guidelines shifting coils towards R-454B and R-32, custom coils need to be manufactured to handle these refrigerants.


At HeatEX Technologies, we carefully consider each of these factors to make sure that every coil replacement is engineered for the specific job and system. Specializing in a wide variety of coils and jobs, we understand that successful custom coil replacement accounts for performance, not just size. Explore our website for more information on how we can assist with your next replacement job. 

Works Cited

KCL Systems. What Is a Custom Coil in HVAC? Behind the Scenes of Precision Coil Fabrication. KCL Systems, https://kclsystems.com/what-is-a-custom-coil-in-hvac-behind-the-scenes-of-precision-coil-fabrication/.


CFM Distributors. How Do You Select and Design a Custom Coil Replacement? CFM Distributors, https://rc.cfmdistributors.com/helpful-tips/how-do-you-select-and-design-a-custom-coil-replacement/.


Precision Coils. Coil Dimension Guidelines. Precision Coils, https://www.precision-coils.com/resources/coil-dimension-guidelines/.

Why Coil Replacement Jobs Get Delayed, and How to Prevent Them

By Colby Maun • August 17, 2026
Delays in a commercial HVAC coil replacement project are one of the most frustrating things that a facility manager or contractor can face. A failed coil already creates problems such as comfort issues, downtime, and pressure from building owners, so making sure that your coil replacement project goes smoothly and without delay is crucial. To assist you with your next coil replacement job, here are some common causes of commercial HVAC coil replacement project delays and how you can prevent them in your job.

Chilled Water vs. Hot Water Coils: What's the Difference?

By Colby Maun • August 11, 2026
Commercial chilled-water and hot-water HVAC coils appear almost identical on the outside; however, they are more different than most people think. Both are water-based heat transfer components, but they work opposite each other and are better for different applications. Here is a full breakdown of the differences between chilled water vs hot-water coils, and how to decide which to use for your application.

Understanding Fan Coil Units

By Colby Maun • August 3, 2026
For buildings that require targeted zoning, such as hotels, offices, apartments, hospitals, retail spaces, and more, fan coils can assist in maintaining a comfortable indoor temperature. Each fan coil unit serves a particular space, which allows individual occupants to control their area of a building without affecting the rest of it. Understanding fan coils and how they work can help facility managers of these styles of buildings more properly maintain and replace units to prevent downtime in their systems. Here is a breakdown of how they work, the different types, and the common problems that they run into in their life cycle.

Which Material is Best for your Coil?

By Colby Maun • July 27, 2026
In commercial HVAC, one of the largest yet overlooked aspects of a custom coil replacement job is the materials that the coil is made of. Different materials thrive better in different systems and environments, which affects the lifespan and efficiency of the coil. Making sure that your replacement coil is best suited for your unique system and location is integral to any facility, and failure to do so can increase costs and decrease reliability. Here is a breakdown of each material in your coil and what scenarios to select each in.

What Actually Goes into Measuring a Coil

By Colby Maun • July 20, 2026
For any coil or heat exchanger replacement job, one of the first steps in the process is for HeatEX Technologies to measure the existing coil/heat exchanger to ensure a perfect fit in the unit. Recently, I had the privilege of going out to my second job site to take measurements with HeatEX Technologies. Here is my account of what actually goes into measuring a coil, and my experience from start to finish.

Trane CGAM070 Microchannel Conversion Case Study

July 13, 2026
After multiple refrigerant leaks sprang from a Trane CGAM070 air-cooled chiller in West Palm Beach, FL, our customer faced a difficult challenge. They had to decide whether to replace the failed microchannel condenser coils with new OEM microchannel coils or pivot and invest in a different, longer-term solution. After much evaluation, our customer decided to convert the chiller from aluminum microchannel coils to copper tube aluminum fin condenser coils.

The Biggest Takeaways from the 2026 ASHRAE Annual Conference for Commercial HVAC

By Colby Maun • July 6, 2026
Last week, from June 27 th to July 1 st , ASHRAE held its 2026 Annual Conference in Austin, TX, and brought together more than 2,233 HVAC professionals from all over the world. The conference covered a broad range of many topics prevalent in the industry today, from fundamentals and applications to AI in building design and construction. Here are some of the biggest takeaways from the 2026 ASHRAE Annual Conference for commercial HVAC.

5 Warning Signs Your Coil Needs Replacement

By Colby Maun • June 29, 2026
In a commercial HVAC unit, coil failure is one of the most frequent and costly problems a system can have. Coil failure in a commercial HVAC unit leads to performance, efficiency, and reliability issues, making it one of the most important aspects in the system. Coils can fail for many different reasons, and understanding when a coil is starting to need replacement can save facility managers tons of extra downtime and stress. Here are 5 warning signs that your commercial HVAC coil needs replacement, so that the next time your coil fails, you can be on top of the problem.

How Aging Infrastructure is Challenging Commercial Buildings

By Colby Maun • June 18, 2026
As a building gets older, it becomes much more likely to experience several different types of HVAC failure, which results in decreased efficiency and reliability in the system. Considering the fact that most commercial buildings in the US were built between 1970 and 2000, this aging infrastructure is becoming increasingly problematic in the world of HVAC. To increase difficulty, many organizations postponed renovation and retrofit projects during COVID and during times of economic uncertainty and inflation. Those decisions extended HVAC equipment beyond its initial design life in many cases, and now that it is finally time to renovate, there are significant challenges to doing so in those buildings. With today’s rising equipment costs, aging building stock, high energy costs, sustainability pressures, and limited budgets, many facility managers are burdened with attempting to keep their equipment running smoothly. As HVAC systems age, they experience coil degradation, efficiency losses, corrosion, and increased failures and downtime in general. Coils are usually one of the first parts to deteriorate, as they are exposed to plenty of different weathering aspects in the air, such as salt, moisture, and pollutants, to name a few. When a coil deteriorates, it reduces system capacity as a whole. Efficiency losses in older units are common as well, since with time, the unit has to work harder and harder to remain operating at the same capacity as it was when it was new. Reliability decreases for units due to increased unexpected failures and downtime, along with it becoming harder to source parts for repairs as technology advances and changes.

YCAV Air-Cooled Chiller Conversion Case Study

June 11, 2026
Location: Hotel – Fort Lauderdale, Florida  Overview: A 6-year-old York YCAV air-cooled chiller serving a hotel experienced premature condenser coil failure. Out of 10 total coils, 4 had already failed (40%), with the remaining coils showing active corrosion. The unit operates continuously, making reliability critical for guest comfort