What is Circuiting and How Does it Effect a Coil?

Colby Maun • August 24, 2026

In a commercial HVAC custom coil replacement job, circuiting is often undervalued, yet so crucial to effective operation in any coil. But what really is circuiting, and how does it affect your coil? Here is a breakdown of everything you need to know about circuiting for your next replacement job.

In simple terms, circuiting is the number of tubes on the coil that attach to the headers. It refers to how the tubes within the coil are divided and connected to create flow paths for the fluid to move through the coil. Determined by fin height and performance requirements, circuiting affects a wide variety of coil aspects such as heat transfer, pressure drop, fluid velocity, and temperature distribution, to name a few. The fluid needs sufficient time in contact with the coil tubes in order to transfer heat, and since circuiting affects how much fluid flows through each coil section, it plays an integral role in heat transfer. A difference in the number of circuits alters how much resistance the coil needs, which impacts the pressure drop for the coil as well. The fewer the circuits, the more fluid goes through each individual circuit, speeding up the fluid velocity in the coil. Circuiting impacts the temperature distribution in the coil as well by distributing the fluid evenly throughout the coil. Making sure that the circuiting in your coil fits the existing system goes a long way toward reliable system operation.

A coil with fewer circuits will have a higher flow per circuit, fluid velocity, and pressure drop. It will also create a longer fluid path inside the coil, as fewer connections back to the headers create a longer path that the fluid needs to run through before it cycles. In contrast, a coil with more circuits would be expected to have a lower flow per circuit, fluid velocity, and pressure drop. This happens because the more tube connections back to the headers in the coil, the less velocity and pressure drop you need to move the liquid through the tubes. Additionally, a coil with more circuits has a shorter fluid path.

Circuiting is especially important in evaporator coils, since the refrigerant in them undergoes a phase change as it moves through the tubing of the coil. Proper distribution of the refrigerant across the coil assists with maintaining the intended operating conditions throughout the coil. In most coils, circuiting is determined for the coil based on elements such as required capacity, airflow, entering/leaving temperatures, and operating conditions, among others. When manufacturing a custom replacement coil, circuiting is one of the less visible coil design aspects. This reinforces that a commercial HVAC custom coil isn’t all exterior dimension-based, and there is much more that goes into it than assumed.

At HeatEX Technologies, we want to make sure that you’re prepared for your next coil replacement job. Knowledge of circuiting assists you in understanding your system better, which allows us to provide you with quick lead times and excellent service. The next time you have a commercial HVAC coil that needs to be replaced, give HeatEX Technologies a call, and we can provide you with a custom replacement coil that has the exact circuiting your system requires.

< Older Post Newer Post >

Condensation: Why Commercial HVAC Coils Produce it and What Happens to It in Your System

By Colby Maun • October 12, 2026

When facility managers think of commercial HVAC cooling coils, they typically think about their primary purpose: lowering air temperatures in certain zones through heat transfer. What’s often overlooked is how cooling coils also reduce moisture from the air in addition to lowering air temperatures. This often causes condensation to form on the surface of the coil. But why specifically do commercial HVAC cooling coils produce condensation? And what happens to it after it forms? During operation, it's normal for condensed water to form on a commercial HVAC cooling coil's surface. This happens when the warm exterior air meets the cold surface as it passes over the coil. As it passes along, the coil absorbs the heat from the air, which lowers the temperature of the air. Something that also contributes to the equation is the air's dew point, which is the temperature at which air must be cooled to become completely saturated with water vapor. In this scenario, the air's dew point being warmer than the coil surface causes water vapor to begin condensing on the surface, forming the liquid you see on the coil. The condensation produced then allows the system to remove humidity from the air, which both improves indoor comfort and helps maintain the desired temperature.

The 2026 ASHRAE Building Decarbonization Conference and What it Means for Commercial HVAC

By Colby Maun • October 5, 2026

From September 23 rd -25 th , ASHRAE held a building decarbonization conference in Seattle that moved decarbonization from simply a long-term goal to an implementation issue. One of the many things discussed was the topic of existing buildings and how to reduce carbon emissions in them through retrofits. Since decarbonization is now being stressed as an implementation issue, below is everything you need to know about what this could mean for the future of the commercial HVAC industry, as well as what you can do to reduce emissions in your own system. Building decarbonization involves reducing greenhouse-gas emissions that are associated with building operations such as HVAC and other systems. This topic is not new to the industry and has been repeatedly discussed within previous ASHRAE conferences and new government regulations. A large aspect of decarbonization comes from building energy use, since lowering building energy use decreases the operational carbon emissions inherent in the building. Previously existing buildings account for the majority of the issue, since new buildings most likely already contain technology that helps to reduce building energy and strain on the system.

Commercial HVAC's Skilled Labor Shortage: What You Can Do About It

By Colby Maun • September 23, 2026

A recent survey done by ServiceTitan found that of 1,000 construction leaders, labor shortages and rising overhead costs are among the top profitability concerns for 2026. Additionally, an estimate by JLL cites that 2.1 million skilled-trade positions, including HVAC technicians, could go unfilled in the U.S. by 2030. The commercial HVAC industry has a looming challenge of a skilled labor shortage, which may change the way that commercial HVAC projects are planned, executed, and maintained in the future. Below is everything you need to know about the effect of this problem on the commercial HVAC industry, and some measures you can take to get ahead of the curve.

How to Properly Winterize Your Commercial HVAC Equipment

By Colby Maun • September 16, 2026

As temperatures begin to cool down this fall, an important part of facility management is making sure to winterize your commercial HVAC equipment. Winterization may be the most important aspect of preventative maintenance to make sure your coil maintains a long and efficient life, and failure to do so can result in costly damage. Winterization prevents freeze damage to the coil, which in turn prevents damage such as tube ruptures, damage to the headers, and leaks in the tubing of your coil. Below is how to winterize your coil, and other important aspects when it comes to winterization maintenance.

How to Read and Understand a Commercial HVAC Coil Schedule

By Colby Maun • September 8, 2026

A coil schedule is a table included with mechanical drawings and specifications that summarizes the performance requirements and physical characteristics of the HVAC coils within the building. It comes with almost every type of coil and is an incredibly crucial piece within replacement projects. Understanding how to read it can drastically speed up your replacement process and reduce downtime in your next replacement project. Because of this importance, here is a comprehensive guide on how to read and understand a commercial HVAC coil schedule. One of the most important parts of a coil schedule is the coil identification section. It acts as the starting point for identifying the specifics of the coil you’re replacing in a replacement job. This section gives information on the coil tag, equipment tag, location of the coil, type, and designation. The coil tag, especially, is key because it often provides you with the model and serial number. Each of these parts is essential information to identify the coil, and when given this information, HeatEX Technologies can often provide you with a quote without having to come out and measure the coil. This saves a ton of time on both ends when getting you your replacement coil.

Common HVAC Coil Installation Mistakes and Their Effect on Your System

By Colby Maun • August 31, 2026

In a commercial HVAC coil replacement project, installation is a key factor that impacts both the performance and lifespan of the coil. A coil can be manufactured and selected perfectly for your replacement job, but if the installation is poor, your coil will experience lower performance and possibly a reduced lifespan. Because of this, making sure that installation goes as smoothly as possible is crucial for your system. To assist you with your next coil installation, here are some common commercial HVAC coil installation mistakes and how they affect your system in the long run. One of the most common mistakes that technicians can make in a coil replacement project is installing the coil in the wrong orientation. Coils are manufactured to operate in a particular orientation, and if they aren’t installed in that specific orientation, heat transfer efficiency and capacity are reduced. Installing a coil in the wrong orientation also affects airflow, since installing a coil in the wrong direction can force air in the wrong direction. Both of these complications negatively affect performance and lifespan in your system.

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.