What is Circuiting and How Does it Effect a Coil?
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.
