Case Study – Replacement DX Coils at local Mushroom Farms

Replacement DX Coils: To those not aware, Kennett Square, PA is the mushroom growing capital OF THE WORLD! Kennett Square is also located quite close to Capital Coil’s sales office in West Chester, PA, and we get multiple requests per month to personally come out and measure DX coils that need to be replaced at these farms.

Mushrooms need a well-ventilated growing environment, and poor ventilation can lead to higher levels of CO2. Higher CO2 levels negatively affect mushroom quality and growth. Ensuring proper air circulation is essential for maintaining healthy crops. Mushrooms also thrive in high-humidity environments, but excessive moisture can also lead to mold or bacterial growth, which can damage the entire crop. Proper humidity control is crucial to maintaining the right balance and preventing costly losses. To tackle these problems, growers need reliable climate control systems, and that’s where Capital Coil steps in.

Mushroom cultivation, while lucrative, is not without its challenges. Running climate control systems for mushroom farming can be expensive, especially when using inefficient equipment. High energy costs can eat into profits, particularly for smaller, family-owned operations. One of the biggest challenges for mushroom farmers is making sure that the coils are working at peak efficiency because the conditions in and around those farms will corrode the aluminum fins at a faster pace than most other environments. As mentioned above, there are very specific conditions that need to be maintained for a successful crop, so the coils in the condensing systems that are needed to sustain those conditions have to be working at all times. 

One farm had been trying to repair numerous coils through different “band-aid” methods. None of these attempts worked, and the farm’s energy costs had skyrocketed when trying to get the same capacity from a failing coil.  One of the neighboring farms that had used us for numerous DX coil replacements recommended that they call Capital Coil to come out and assess the failing coils.DX Coils

After looking at a few of the units, most of the coils’ finned area had been eaten away by corrosive elements in the air. The OEM had not recommended any protection for the coils, which was why they failed far sooner than they should have. The new coils were to be installed in the original units, so the measurements needed to be exact. I also explained to them that any new coil(s) needed to either have more durable materials, such as stainless-steel casing and/or copper fins, or a protective coating for the whole coil. If not, these same issues would continue to occur.

The farm decided to order (1) DX coil with an epoxy coating as a “test” before ordering the rest. The new DX coil arrived a few weeks later and was a perfect match for the original unit. A year later it was still running at max capacity with zero damage to the finned area because of the coating.

Due to the speed that we were able to come out to the site, correctly assess the reasons for the coil failures, and make recommendations on increasing the coil’s longevity, they decided to order the remaining batch of DX coils from Capital Coil & Air. They also recommended us to many of the other farms in the area, so Capital Coil is now the main HVAC coil replacement company for many of the largest mushroom farms in the United States.

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Top 10 Chilled Water Coil Facts

Every Chilled Water Coil selection is about balance. Your coil selection balances the rows/fins versus the cost of the coil pressure drops/performance. Trying to cut corners on your initial selection may save you money upfront, but you will inevitably pay it back down the line through added energy costs. This is a truism for every manufactured coil.

  1. Fins cost less money than rows/tubes. A good cost-cutting tool when selecting a coil is to choose 14 fins/inch. This will turn your (8) row coil into a (6) row coil, which will dramatically lower your costs. If you choose to go this route, one thing to keep in mind is that 14 fins/inch will be semi-inconvenient to any maintenance crew tasked with cleaning the coil. Don’t expect a Christmas card from them that year.
  2. That raises the question of whether or not you can even clean a deep (6) or (8) row coil? In short, you can, but it is not easy. Chilled water coils are especially difficult to clean because they are almost always wet. Due to this fact, they typically attract dirt and additional particles that other coils do not. Generally, when cleaning a coil, most of the dirt get pushed to the middle, and for that reason, 14 fins/inch may not be the best idea after all. Chilled Water Coils
  3. Did you know that fins do approximately 70% of the heat transfer in a chilled water coil, while the tubes are only responsible for the remaining 30%? This is precisely why the fin/tube bond is so important. Without a perfectly crafted fin/tube bond, coils become inefficient very quickly. You pay for that inefficiency through increased energy costs.
  4. How long does a coil last? At what age can I expect my coil to fail? Unfortunately, there is no single answer to either question. Everything is dependent on a combination of maintenance, duty, and numerous other factors. If your initial selection was correctly chosen, and proper maintenance was kept, 15-20 years is a good timeframe.
  5. You may have a situation where your coil is 20 years old, and everything appears to be operating in good condition. There are no leaks and all looks ok. However, over that length of time, what you don’t see is that the fins have thinned and are no longer bonded to the tubes, and the coil is dirty in places that you cannot see. Again, while the coil may look to be running in top form, it’s probably only running at 60% capacity. Most likely, the tubes have also thinned over time, so when the next deep freeze occurs, you can guess the likely outcome.
  6. You really need to replace the coil, but have been told to make do with the current coil? To make up for the lack of efficiency, you might try to “jury-rig” your system. One method is to change the drive on the fans to deliver more CFM. This increases the air pressure drop, which in turn increases motor brake horsepower. Another option to help increase the coil’s efficiency is to lower the temperature of the chilled water from the chiller. We tend to mess with the system and apply temporary Band-Aids, when replacing the coil is the only guaranteed long-term solution.
  7. If you want to spend money wisely on a chilled water coil, simply make the tubes thicker. The tube thickness for a 5/8” tube coil is .020” thick, so increase the tube thickness to .025”. The same applies for a ½” tube coil, with a tube thickness of .016”. Increase it to .020”. By doing this, you get the added bonus of making your return bends thicker, which also helps to extend the life of the coil.
  8. Not quite sure about circuiting on a chilled water coil? You are going to have a hard time making an accurate selection unless you understand how to circuit a coil. Circuiting is really nothing more than selecting the number of tubes that you want to feed, and how many passes the water makes through the coil – depending on your GPM. Circuiting is one of the most important factors in ensuring that your coil is running at peak-performance.
  9. Curious about the balance between cost, size, materials, and maintenance? Every chilled water coil needs to be maintained for its entire life-span. If you’ve made your selection, and something seems off about the coils, chances are mistakes were made during the selection process. Some indicators include the coil being too big for the space allowed, or incurring out of control energy costs. What is the point of saving $500 on a chilled water coil if you have to spend $5,000 in maintenance over its life-span?

As coil replacement experts, we run into this issue every day. Our goal is to work with you to ensure your selections are correct the first time. The person in charge of budgets will be grateful to you over time. Capital Coil & Air welcomes the opportunity to work with you on your next coil project! We want to be your coil replacement specialists.

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Now Offering R-454B Refrigerant for All DX Coils

In keeping with most of the OEM’s in 2025, Capital Coil is helping everyone transition from R-410A over to R-454B refrigerant in their DX Coils. Whether you are designing a new system, or retrofitting an existing one with a condensing system, Capital Coil can help in making the switch in refrigerants.DX Coils

If you are not yet aware, the EPA is working hand in hand with many of the major OEM’s to help reduce commercial HVAC’s carbon footprint. One of the major ways in which HVAC manufacturers are helping and complying with the new industry standards is the gradual change in refrigerants from R-410A to R-454B. Beginning in January, 2025, no new system is allowed to be built or imported using the older refrigerants. Without going into a deep dive on the differences, R-454B offers a lower GWP (global warming potential) alternative to R-410A. Hence the mandate to change to that refrigerant type. 

However, Capital Coil will still offer R-22 and R-410A for DX Coils in older systems that might not be compatible with R-454B. In other words, Capital Coil has been, and will remain, the most reliable source for all commercial and OEM replacement coils. Our #1 job is to make to your job easier, so please reach out. You will be glad you did.

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How Should Steam Coils Be Designed??

Steam coils

Of all of  the various types of coils, steam coils operate in the most complicated ways. They are, in effect, a product of the system and controls around the coil. If not installed correctly, steam coils simply won’t work properly.

Overview:

The object of any steam coil is to have steam enter the coil as steam and exit as condensate. In a perfect scenario, the BTU load on the coil turns steam into condensate just before it’s ready to exit the coil. Under real world conditions however, condensate usually begins to form inside the tubes almost immediately. Especially when dealing with low-pressure systems, you have to find a way to evacuate the condensate from the steam coil.

Coil Pitch: 

A good coil manufacturer will internally pitch the steam coil within the coil casing to force the condensate toward the outlet connection. This pitch is usually 1/8 “ per lineal foot of coil.

Coil Length: 

If you require steam to travel 144” and make multiple passes through the coil, then, simply put, your system will not work properly. Condensate forms too early, and it cannot escape the coil. Because of this, coils cannot be too long. A better strategy is to break one long coil into two smaller coils side by side, while feeding from both sides.

Tube Diameter:

Steam Distributing coils often have to be 1  1/8 ” diameter tubes. If the BTU load on a coil is really large, then as a result, you will generate many more Lbs./hour of condensate. If the tube diameter is too small, then the condensate, which needs to evacuate, has no place to go.

Traps:

Traps are required on steam coil systems. The traps should be “float & thermostatic” type traps and be located 18 “ below the condensate connection on the steam coil. Without this, the condensate just sits in the system without any place to go.

Vacuum Breakers: 

Vacuum Breakers are often installed in coil systems to remove any excess condensate that may remain within the coil.

Insulated Piping:

There is no such thing as a “Condensate” Heating coil, built as a steam coil. IT DOESN’T WORK.  However, and this happens an astounding amount of times, due to the long distances the steam has to travel from the boiler to the coil, many times, the steam will enter the coil as condensate due to the piping not being insulated.

Anything that makes condensate lay in a coil is harmful to both the steam coil and the system. You will get a “water hammer” when the system is turned on and the incoming steam just blasts against the condensate. Worse than the loud and annoying sound that produces is the fact that it just destroys the steam coil. The brazing was never designed for “water hammer”.  Also, the coils do not heat properly. Have you ever seen a long coil and run your hand down its length only to feel that the entering steam end of the coil is hot but the far end is cold? More times than not, this means that condensate is laying in the coil and not allowing the steam to properly travel the length of the coil.

Steam Coils require a real expertise to design & build. We at Capital Coil have a long history in solving coil problems and building steam coils so that they work correctly the first time. Give us a call for your next job – you’ll be pleasantly surprised!

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Frozen Steam Coils: How Do You Prevent This?

Regardless if you have steam coils or steam distributing (non-freeze) coil, you can freeze ANY coil.  When freezes happen, everyone immediately looks to the steam coil as the cause.  When in fact, there are numerous reasons that must be looked at well before the coil.

Freezes generally happen in older systems, however if your new system is not maintained properly or correctly installed, your steam coil can and will freeze.  For instance, you’d be surprised at how many times dampers are left open, controls fail, freezestats don’t work, etc.Steam Coils

In a Standard Steam or Steam Distributing Coil, a freeze-up can occur when condensate freezes within the tubes of the steam coil.  The two most common reasons for freezing steam coils are the steam trap and the vacuum breaker.  The function of steam trap is to remove the condensate as soon as it forms.  Condensate usually collects in the lowest part of the coil.  If your steam trap isn’t installed properly, that condensate will lay in the coil and it will inevitably freeze as soon as it sees outside air.  The vacuum breaker also helps clear the condensate, minimizes water hammers, and helps with uneven temperatures. This must be installed on the control valve and always above the steam trap.

Unfortunately, there are no ways to determine exactly where your steam coil will freeze.  And a common misnomer is that the condensate turns to ice and the expansion is what causes the tubes of the coil to pop.  In reality, it’s the pressure that builds up between freeze points.

Here’s couple tips in your coil design that can help prevent your standard steam and steam distributing coils from freezing:

  • Standard steam coils should NEVER see any outside air below 40 degrees.  If it does, steam distributing is the only way to go!
  • 5/8” OD Steam distributing coils over 72” long are recommended to have a dual supply
  • 1” OD Steam distributing coils over 120” long are recommended to have a dual supply
  • Make sure your steam coil is pitched if possible.  This slopes the condensate to the return connection making it easier to remove the condensate

Give Capital Coil & Air a try on your next project. Our engineering, pricing and service is the best in the industry!

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Cooling Coils & Moisture Carryover

Moisture carryover is present on cooling coils where dehumidification happens.  Many people do not think it’s a problem…until you have moisture running down ductwork or spewing all over the inside of an air handler. If you’ve ever experienced that then you probably know all of these rules regarding moisture carryover.

  • Entering air temperatures of 80/67 of return air in the Northeast carry far less moisture than an outside 95/78 entering air temperature in Florida. Outside air always has more moisture. Cooling Coils

    -Your location plays a part as well. The drain pans will absolutely have be sized differently. Florida’s will be much larger in size.

  • Fin design is irrelevant when it comes to moisture carryover. Whether you have copper corrugated fins, or aluminum flat fins, plate fins or even the old fashioned spiral fins, none of it has any effect on moisture carryover.
  • Lastly, be careful when installing a new chilled water or DX (Evaporator) Coils in a system. Many end users like to increase the airflow on older coils because those old coils can act like filters, the fins are covered in dirt/dust and you’re not getting the same airflow through the coil. This dirt on the coil also semi-prevents moisture carryover. When that brand new chilled water coil is installed, the airflow might be higher than that of 550 ft/minute, which of course will cause moisture carryover problems. 

Please give us a call with any questions about your coil, your system or its design. Capital Coil is here to help you avoid situations like the one described in this post, and we would love for the chance to work with you!

 

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What Is Meant By A “Bank” Of Chilled Water Coils

For those that work with HVAC installations on a regular basis, you have run across the problem of needing to install new chilled water coils in very tight, confined areas. The coil is too big to fit in the Chilled Water Coilselevator, and/or the HVAC room is so small that you are likely to damage the coil simply by moving it. As a solution to this challenge, chilled water coils are often installed in “banks” of coils. You are most likely to see this configuration in Air Handler Units, as well as “built-up” systems. Due to face velocity limitations across the coil, you will need larger coils in order to meet your required face area. With this in mind, there are a few specific reasons why you want to avoid having a single, large coil in one of your units.  Starting with the obvious: larger coils are much more difficult to transfer and install. This is especially true for older buildings, where the rooms were essentially built around the HVAC system.

As you’ve probably experienced, some of these areas can barely fit a single person, so installation – if even possible – is a logistical nightmare. Also, the larger the coil, the easier it is to damage during transport to the jobsite. To avoid these issues, simply break down the single, larger coil into smaller coils. When piped together, those smaller coils are stacked into “banks” of coils in the system. If installed correctly, this “bank” should have the same performance as the larger, single coil.

Casing

There are many different casing options available, but “stackable” flanges are required for heavy chilled water coils that are “banked”. The flanges are often inverted inward and down to give added strength to the casing, which is needed due to the fact that another coil of equal weight will be stacked on top of it. When ordering coils in a “bank” configuration, be sure to let the manufacturer know that they will be “stacked”.

Many engineers also use stainless steel casings on chilled water coils. While more expensive than traditional galvanized steel, stainless steel protects against excessively wet coils and/or corrosive elements in the airstream. Keep in mind that the majority of coils fail because of old age and its casing, as opposed to failure with the coil’s core. With that in mind, doesn’t it make sense to select heavy-duty stainless steel casings that are more durable and meant for stackable installations?

Drain Pans & Water Carryover

Water Coils

All chilled water coils must be sized so that the face velocity across the coil does not exceed 550 ft/minute. Water on the outside of the coil is carried away from the coil’s leaving air side in an arc, while water in the highest point of the coil is carried further down the unit or ductwork. “Stackable” coils often require intermediate drain pans under each coil to catch the excess water carryover. Each coil in a bank requires its own drain pan, as a single, large pan under the bottom coil is not enough.

Circuiting/GPM

If all of the coils in a “bank” are of equal size and handling the same CFM, then the GPM of each coil will also be the same.

Always feed the bottom connection on the supply header on the leaving air side of the coil. This ensures counter air and water flow. This also prevents the coil from short circuiting because the header fills first and circuits all of the tubes equally.

Designing Banks Of Coils

Almost all coil “banks” perform more efficiently if you design something more square in shape, as opposed to long and/or high. In a “bank” of coils, you may find that one coil has points of 300 ft/minute, with other points at 800 ft/minute. Scenarios such as this will cause water-carryover! You generally want to be as close to 550 ft/minute as possible in order to allow equal airflow distribution across the face area of the coil.

Anytime you are designing and/or building coils, work closely with the manufacturer as an added resource to ensure that you are getting the ideal solution for your HVAC system. Capital Coil & Air works on similar jobs such as these daily, and we welcome the opportunity to work with you in whatever capacity is needed.

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Condenser Coils Failing? Here’s probably why….

Did you recently turn on your DX systems only to find your Condenser Coils are not working?  Simple fix right?  Unfortunately, no.  If you get lucky, you can send us the model number of the unit, and there’s a great chance we’ve already built it.  In the case that we do not have that model number on file, you have two options.  You can go back to the OEM, wait (5) months for a part and pay through the roof.  Or you call Capital Coil, and we’ll walk you through the engineering it takes to replace a condenser coil.                                                                      Condenser Coils

Very rarely do condenser coils ever freeze so the first thing you’re going to want to know is if your coil died of corrosion, old age, or possibly vibration.  Old age is obviously preferable because with a few easy dimensions, we’ll have enough to price up your duplicate coil.  Condenser coils are usually outside and are easily accessible for measurements and digital pictures.  With just the size, the rows, and fins/inch, you can get a price.  And digital pictures of the headers and return bends will give us a good idea of the circuiting and sub-cooler circuits. 

If the coil has been eaten away by corrosion, it was an improper design to begin with.  Most people don’t know that salt in the air will ruin aluminum fins within a year or two.  There are two ways to combat this.  The first option is to make the switch to copper fins and stainless steel casings.  While this will extend the life of your coil considerably, most people are not too happy about the additional cost over aluminum fins.  The second option is to use a coating.  Coatings are the much more popular choice.  They are a fraction of the cost as copper fins and only add (1 – 2) weeks to your lead time. 

When your HVAC coils are installed near a moving piece of equipment, vibration can occur and cause leaks.  The area where these leaks occur is very important and will clue you in to if the problem is vibration.  If they are near the tube sheet and look like they are slicing through the tube, 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.

The last concern is with cleaning condenser coils.  Since condenser coils see outside air almost exclusively, they need to be cleaned more than other coils.  The reason for this is most condenser coils have fin spacing of 12-20 fins/inch.  With fins that tight together, the coil can and will act like a filter.  And when the coil is clogged up, the performance suffers greatly.  Recently, we’ve been getting more and more calls about using a heavier fin thickness.  This is to help with high pressure cleaning and corrosive cleaning agents. 

When dealing with an HVAC coil manufacturer, 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 has seen every issue to make sure your everything from the quote to the installation go smoothly! Give us a try on your next project!

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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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