Top 10 Tips For Measuring HVAC Coils

1. When measuring HVAC coils, performance has very little to do with accurately measuring for replacement coils. Fitting the coil in the existing space with the least amount of labor has everything to do with measuring a coil.  If you duplicate the coil in almost every respect, the performance will match and take care of itself.  New is always more efficient than old.

2.  If you’re ever in doubt about a dimension, smaller is always better than bigger. You can always “safe off” around any coil as long as you can fit it in the space.  If a coil is too big, it makes a really ugly coffee table in your shop.  Too big is the enemy of measuring coils.

Chilled Water Coil

3.  The fin height and fin length are not the determining factors in measuring a coil. The overall casing dimensions are the most important, and you work backwards to determine fin dimensions.

4.  The depth of any coil is the total casing depth in the direction of airflow. The height is the number of tubes high in any row.  Depth is a function of rows deep and height is a function of tubes in a row.

5.  Overall length (OAL) is not the fin length and it’s not the casing length. It is the length from the return bends to include the headers that are inside the unit.  Again, it is necessary to work backwards to get the other dimensions once you know this critical dimension.

6.  Circuiting is the number of tubes connected to the supply header. Generally, you just want to count the number of tubes connected to the header and that will tell you whether it’s full, half, or even a double circuit.  It does not matter how the return bends are configured.  Your goal is to count the number of supply tubes and all performance is based on that.

7.  Fins are measured in fins per inch. Hold a tape measure up to the coils and count the number of fins in one inch.  If you can’t get in to take the measurement, a safe rule of thumb is 10-12 fins/inch.  That will work on almost every coil.  The exception to that rule is a condenser coil.  14-16 fins/inch on a condenser coil is usually pretty safe.

8.  Connection locations are difficult only if you are using the existing piping in the system (which are welded). Copper piping is brazed and can be changed easily.  If a system is old and the piping is being replaced as well as the coil, the connection location is not a major deal.  It’s very easy to match up!

9.  With replacement coils, the concept of “left hand vs. right hand” doesn’t actually exist. Connections are “top left-bottom right” or vice versa.  Ideally, all coils should be counter-flow which means that the water and air flow in opposite directions.  The air hits row one first and the water is piped into row eight first.  However, there are lots of installations that are piped backwards, and they work just fine.  Just match them up, and the coil’s performance will be equal to the old coil.

10.  Connections are not measured from the top of the header! They are measured from the top of the casing to the centerline of the connection.  Or the bottom of the casing to the centerline.  You need a point of reference, and the header height can be anything just as long as it doesn’t stick above or below the casing height.

 

All of the above “suggestions” or “secrets” are in no particular order.  They are just things that you should know to ensure that you are selecting the correct replacement coil. While most seem like common sense, your best bet is to talk with the sales team at Capital Coil & Air, who can walk your through the entire process and help you to fill out coil drawings when trying to measure the dimensions.

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Do You Need to worry about performance on replacement HVAC coils?

With replacement HVAC coils, performance is almost never the issue. This is a common mistake that a lot of folks make. When duplicating a coil, your efforts need to be directed towards making sure the coil fits correctly, as that’s usually the main issue. While you may be thinking that doesn’t make a whole lot of sense, here are the main reasons:

  • Coils were never intended to be filters, but that’s exactly what they become over time. For those that routinely work with coils, you know its design is tailor-made for the collection of dirt and Water Coilother air particles The tubes are staggered, which means that dirt can not get through. The fins are rippled and corrugated, which typically leads to the same result. Wet coils tend to collect more dirt than dry coils. The process of cleaning coils is very difficult, and the deeper the coil, the more difficult it is to clean. The end result, depending on the age, maintenance and operation, means that your coils operate anywhere from 50%-70% of their maximum efficiency.
  • Fins do approximately 70% of the work in a coil, with the tubes making up the remaining 30% (generally). When manufactured, the tubes are expanded into the fin collars. But, over time, the fins tend to loosen a little. While not sliding back and forth, the fins lose efficiency and their performance is lessened.
  • So what’s your typical solution after 5, 10 or 15 years? You’d probably raise or lower the water temp on you coil. You might also speed up the drive to get more CFM across the coil. You’ll try most anything to make up for the loss of the coil’s efficiency. Everybody does.
 

But when you replace the coil, it’s new and clean. Additionally, with a new fin/tube bond, your new coil is operating at 100% efficiency, while the old coil was working at 60% – 70% efficiency…maybe. With this automatic increase in efficiency means that performance is not really the issue. Your main concern should be that the coil fits in the space available. Otherwise, your new coil is nothing more than an ugly, metallic coffee table.

Your main goal is to replace your coils with as little trouble and cost as possible. While you may still have offsets in piping, as well as other small installation adjustments, performance should be the least of your worries. We’re here to help you meet your requirements quickly and easily.  CALL OR E-MAIL US!  We look forward to the opportunity to work with you on your future projects.

 
Replacement HVAC Coils

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Top 5 Reasons Commercial HVAC Coils Prematurely Fail

Capital Coil & Air has come across virtually every scenario over the years in which a commercial HVAC coil had to be prematurely replaced, and we have since created an easy guide targeting the main reasons HVAC Coils prematurely fail.

  • Coil Plugging: If you are not changing filters and/or your commercial HVAC coils are not properly cleaned in a timely manner, your coil will actually begin to act as a filter. When dirt builds up on the coil, that blockage prevents heat transfer and can cause an approximate 20% to 40% drop in performance. Dirt adds to the coil resistance and can be a primary cause for your coil to fail prematurely.
  • Vibration: When your HVAC coils are installed near a moving piece of equipment, vibration can occur and cause leaks. You can tell if vibration is the main cause if leaks are near the tube sheet and look like they are slicing through the tube. If/when that happens, the coils should be isolated from the rest of the system to prevent vibration from causing damage. One way to combat this is by oversizing the tubesheet holes, but many manufacturers will not do this. Condenser Coils are usually the most common victims of vibration.
  • Corrosive Environment: This applies to both the air in the environment and inside the tubes. For instance, if there is a corrosive element in the air, it will eat away at the copper tubes; whether you have 0.020” wall or 0.049” wall. This is very common in coastal areas where there may be salt in the air. To keep the costs down from going to a stainless steel or cupro-nickel coil, we usually suggest coating the HVAC coils. Coatings are almost always within your budget, and its application will only add about a week to the overall lead time. Steam condensate and untreated water can cause corrosion within the tubes of HVAC coils as well. If you have a steam coil that has failed before the one year warranty, there’s a great chance that corrosive agents are in the steam, and it’s eating away at the copper tubes.
  • Freeze-Ups: Most people think that when HVAC coils freeze, the water or condensate laying in the coil freezes into ice and it expands causing the tubes to bulge and eventually spring leaks. What really happens is that the coil will freeze in multiple areas simultaneously, and it’s the pressure between these areas that cause the tubes to swell and eventually burst. These are very easy to spot as the leaks will run the length of the tube rather than around the tube.  ALSO be very careful when considering “freeze-proof” coils!  If you remove 5-6 inches from the fin length to make the “freeze-proof” application fit, your coil’s performance will suffer considerably. 
  • System Design: You would be amazed to learn how many HVAC coils were never designed properly for their systems. If there is a design problem, replacing the coil will only waste time and money; while you have done nothing other than duplicate the previous problem. A little known fact in the replacement market is that a high percentage of all our projects are because the coils were built incorrectly or were never designed correctly in the first place. In some cases, owners attempt to improve the coil’s performance by adding additional rows. Most however do this without taking into account the air pressure drop or fluid pressure drop that comes with it.

When dealing with an HVAC coil manufacturer, try to partner up with one who will walk you through the engineering and explain it along the way. Capital Coil & Air has well over a decade of experience and can help you diagnose whatever problem that you are experiencing correctly the first time. We look forward to working with you on your next project!

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How Did The HVAC Commercial Coil Replacement Market Originate???

How in the world did the commercial coil replacement market start? This specific newsletter is more of a story than anything technical that we have covered in most of our previous emails or blogs. Rather, this is the story of how one manufacturer’s representative, Robert Jacobs, almost by accident, stumbled upon the concept of the coil replacement market back at a time when the only way one could get a replacement coil was to go through the original equipment manufacturer – (OEM). In full disclosure, Bob Jacobs is the VP of Business Development with Capital Coil & Air.

Way back in the day – (1970’s) – HVAC coils were not stand-alone pieces of equipment as they are considered by some now. Coils were nothing more than a single part in an Air Handling Unit (AHU) or a bank of coils. Like a bearing, a drive, or fan wheel, coils were simply part #’s that one needed to reference with the OEM in order to get a replacement built. This situation was a very good deal for the OEM’s because much like car parts, they could charge upwards of 3x’s the original cost of the coil or “part”. And, it was built according to their schedule/timeline, not yours’.

In the 1970’s, Bob Jacobs was a manufacturer’s rep in the Philadelphia-area, and his main line of equipment was Bohn Aluminum & Brass. Bohn was a division of Gulf & Western and competed against many of the top manufacturers, such as Trane & Carrier. For comparison-sake, Bohn was very similar to what Dunham-Bush is today.Commercial Coil Replacement

During this period, Bob Jacobs was asked by numerous local contractors to replace old and/or broken coils. Due to the lack of a quality alternative, he initially used Bohn for coil replacement projects, but replacing coils was not exactly Bohn’s “sweet spot”. It should be mentioned that during this period, replacement coils were not really on any manufacturer’s radar as a separate product – hence the point of this story. Regardless of the OEM, standard lead-times were upwards of (12) – (14) weeks, and those “replacement parts” were very expensive. It was during this period that he realized that there was serious potential for some kind of HVAC coil replacement market. To test this theory, he initially spent $75.00 on an ad deep within the classified section of “Air Conditioning & Refrigeration News”. It was the old type where one had to “circle the bingo card” to request additional information, and this single ad received over 525 inquiries from across the country!! This eye-opening initial response to his idea made him realize that he had come across something good, but now the challenge was how to satisfy this new market. Bob Jacobs initially contacted Bohn to see if there was any interest in building replacement coils, as well as marketing the idea across the United States. Bohn essentially laughed at the idea and countered that he’d be violating his sales rep agreement by going into the territories of other reps. This was very flawed reasoning as none of the other reps were engineering or selling replacement coils in the first place! Within a week, he had canceled his agreement with Bohn and was looking for alternative vendors. He also decided to run a second ad that received another 450 inquiries; furthering his idea of the need for a coil replacement market.

The next step was to reach out to Singer Coils (yes, like the sewing machine), who was located in North Carolina. Because they had built coils for other manufacturers, he pitched his idea to them along with the request that they build his special or “custom” coils. While initially skeptical of the concept, the doubters were proved wrong as his firm gave Singer over $3,500,000 in business in that first year alone. Admittedly, that $ amount in the first year in a brand new market is impressive whether it’s 1971 or 2021!!

One must also remember that these were the days before fax machines and most certainly before email and the internet. Quote requests for coils were received via USPS and were hand-drawn sketches written on things, such as legal pads, envelopes and pretty much every way imaginable compared with today. Because everything was starting from scratch at this time, there were no coil model libraries or other materials to cross-reference, so going through a random building trying to locate the correct coil to replace could be torturous. However, over the next 6-8 years, his business grew quite rapidly, and he was able to collect and build a substantial reference library of coil drawings and other relevant information. The experiences of the prior 8 years, coupled with his firm’s knowledge of commercial coils, eventually allowed his company to begin building their own replacement coils for the 1st time, rather than relying on a 3rd party manufacturer.

Bob Jacobs’ original coil replacement company developed relationships with literally thousands of customers and laid out the initial blueprint for success in the coil replacement business. Due to that success, you now have approximately (10) alternatives that have attempted to copy his model as it’s become obvious that this is a lucrative market. Even OEM’s have recognized that they need to have a piece of the replacement market. But an important point to remember is that just because a company says or even advertises that they are in the coil replacement business does not mean that they are any good or even fully understand how the replacement market operates. For example, most coil manufacturers today are still more interested in the production of larger quantities, so replacement coils are “special” to them. In other words, sometimes these manufacturers want to be in the coil replacement business, and other times, without telling you, they do not. And not knowing where a company’s focus or priorities lie makes it extremely difficult to work with them under emergency conditions.

Bob Jacobs was there at the beginning and is still quite active within Capital Coil. Having daily access to a resource that literally invented the coil replacement market is what separates Capital Coil from all other competitors. Capital Coil will continue to be your coil replacement experts, and we greatly look forward to the chance to work with you on future projects.

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