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/.

< Older Post Newer Post >

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

HVAC's newest Refrigerants

June 8, 2026

New refrigerant requirements from EPA mandates aimed at reducing greenhouse gas emissions are shaking up the HVAC industry. These requirements are causing a shift from R-410A refrigerant to A2L refrigerants R-454B and R-32. A2L refrigerants are low in toxicity and flammability. The shift is based around a metric called GWP, standing for Global Warming Potential, which measures how much heat a gas traps in the atmosphere compared to carbon dioxide. R-410A has a GWP of around 2,088, which means that 1 pound of R-410A released into the atmosphere has the same warming effect of 2,088 pounds of CO2.

How AI is Reshaping the Future of HVAC

June 5, 2026

Increasing demand for AI, high performance computing, along with hyperscale data center expansion are creating a massive new market for HVAC. The shift is in cooling, as data center cooling is moving beyond incremental airflow optimization, and towards liquid cooling in order to support AI and its specific cooling needs. Because of this, the data center liquid cooling market is projected to expand from 6.6 billion dollars to 38.4 billion dollars by 2033. North America is the current hotspot for this investment as it hosts the largest concentration of AI training clusters globally. Historically, data centers have relied on air-based systems for their cooling, which includes CRAHs, chilled water systems, and precision cooling equipment. Because AI servers are now generating higher heat loads than previously (Modern AI racks can exceed 100 kW per rack compared to the traditional 5-15 kW loads of the past), facilities need heavier duty cooling, sparking the transition to liquid cooling solutions. This transition to liquid cooling is not removing HVAC systems and instead restructures their role within AI facilities. Removing building heat, maintaining environmental conditions, and supporting chilled water distribution systems are all issues that HVAC remains a critical solution to. As a result of this, specialized coils, such as the ones HeatEX produces are growing in demand along with cooling towers, heat exchangers, and other thermal regulation components necessary for dealing with high heat rejection requirements. This trend to support AI with Liquid cooling brings new challenges with infrastructure and compatibility for projects, as operators prioritize power usage effectiveness reduction and carbon footprint optimization. Ensuring coolant compatibility with diverse server architectures, leak prevention, and aligning cooling with rapidly advancing cycles are a few of these challenges. Operators are looking for companies that can specialize towards their plants and customize them to their need.