At Capital Coil & Air, we have an accurate and user-friendly coil selection program to select and choose coils. Of course, making good selections is based on having years of experience working with coils of all types and sizes, and we at Capital Coil have that necessary expertise.
When designing a coil, the object is to balance cost and performance together, and that is one area in which we can greatly assist. We do not always choose the cheapest coil because the cheapest coil in almost never the best coil. There are always pressure drops, materials of construction, performance requirements and a host of other things that all play into good or bad coil selections. These are even more relevant in the coil replacement market!
The object is not to duplicate a problem with a coil, but to instead solve the problem and make the coil perform better and last longer. This requires problem solving and making selections that are not always “in the box”.
Part of any successful selection process is having a good selection program to help you. But what makes a program good? First and foremost, you must get the correct results, or you have bad information that is also useless. But apart from that, the selection program must be easy to navigate through. There are “red lights” and “stop signs” built into the program to keep you from making bad selections. Our selection program has most, if not all, coil configurations and styles that you’re likely to run across. We are confident that you’ll find the selection program user-friendly, helpful, and one that makes you want to do business with Capital Coil & Air.
You simply have to click here to request the program, and we will send you an email in response with an activation code and a link to download the program. Of course we are always here to assist you in any selections that you make, or to give you some engineering suggestions and recommendations. Thanks for giving us the opportunity to help you!
At first glance, fin designs on HVAC coils seem about as exciting as watching grass grow. “Why would I ever care about fin design on any coil” was probably your initial response to our question. Nevertheless, we would not dedicate a newsletter to this subject if fins were not important.
One of the primary reasons fins are so important is that you want to keep your coil as clean and maintained as possible. In order to properly maintain your coil, you need to have an understanding as to how HVAC coils are constructed. While fins do not look like much, they are MUCH more complicated than what you can observe at the entering or leaving airside of the coil.
To begin, fins are responsible for a surprising 65% – 70% of the heat transfer on any coil, while tubes are responsible for the remaining 30% – 35%. Additionally, in order for your coil to work at optimum performance, you need to have a terrific fin/tube bond, (which we will discuss below).
Fins are known as secondary surface, while tubes are referred to as primary surface. While this may seem counter-intuitive, the secondary surface is responsible for twice the amount of heat transfer as the primary surface.
There are special dies (see picture) that stamp out aluminum or copper fins with the correct thickness, height, and depth to make the coil the correct size. For example, a coil might be 36” (height) x 96” (length) x (8) rows deep x 8 fins/inch.
Fin Height: 36”
Fin Depth: 12”, (8) rows deep
# of fins in the coil: 768 (8 fins x 96”)
Each fin has 192 holes stamped in the fin for 5/8” OD tubes (8 Rows x 24 Tubes), and each fin is identical.
Each hole has extruded metal, which is more commonly referred to as the fin collar. The collars are sized to self-space the fins and allow for later expansion of the tube into the fin collar. This practice is also known as “bonding” and is essential to having your coil run efficiently/correctly.
Each fin is rippled at the entering and leaving edge of the fin to help create air turbulence.
Each fin is corrugated in the direction of airflow to allow for greater air turbulence. This is important to remember because turbulence creates heat transfer.
So again, what is the point of understanding the importance of fins in HVAC coils? While coils can be built with flat fins for various reasons, the vast majority of coils are built with enhanced fins. Enhanced fins help to ensure that the airflow is not running straight through the coil.
Regardless of fin type, keep in mind that HVAC coils can and will act as great “filters”. The tubes are staggered and not in-line; while the fins are designed to help break up the airflow and not facilitate an easy, straight-through air path. Dirt and/or other particles in the air get caught easily, which again, is why coils can act as great filters. Additionally, coils with more rows will usually get dirtier than coils with less rows. Lastly, chilled water or DX coils are typically wet coils, which results in them catching virtually everything in the air.
The amount of BTU’s through any coil is in direct proportion to the amount of air through the coil. For example, if you are only getting 90% of the design air through the coil, then you are only getting 90% of the BTU’s.
Coils require good filtration and periodic maintenance. If not done correctly, you’ll pay the price of higher energy costs on an inefficient coil.
By now, you have hopefully come to the realization that HVAC coils are much more complicated than they appear, and that fins are an integral part of the coil as a whole. Again, while admittedly not the most exciting topic, understanding the role and importance of fins in HVAC coils cannot be overstated. Capital Coil & Air is here to help you with any and all coil selections, and we look forward to working with you on your next project.