DX Coil Replacement for Harsh, High-Humidity Mushroom Farm Environments

Kennett Square, PA is widely known as the mushroom capital of the world. It is also located just a short drive from Capital Coil & Air’s sales office in West Chester, PA. Because of that proximity, we regularly receive requests from local mushroom farms to visit their facilities and measure failing DX coils for replacement.

Mushroom farms require precise climate control. Proper ventilation is critical because high CO₂ levels can negatively affect mushroom quality and growth. Humidity must also be carefully controlled. Mushrooms thrive in high-humidity environments, but too much moisture can lead to mold, bacteria, and serious crop losses.

That makes reliable HVAC equipment essential.

The Problem

One local mushroom farm had been dealing with multiple failing DX coils. Instead of replacing them, they had tried several temporary “band-aid” repairs. None of those repairs solved the issue.

As the coils continued to fail, the systems had to work harder to maintain the required growing conditions. That caused energy costs to rise while performance continued to decline.

A neighboring farm, which had already used Capital Coil & Air for several DX coil replacements, recommended that they call us to inspect the equipment.

What We Found

After inspecting several units, we found that the finned area on many of the coils had been severely damaged by corrosive elements in the air. The aluminum fins had deteriorated far faster than expected, which significantly reduced coil performance.

The original equipment had not included added coil protection, which made the coils vulnerable in such a harsh environment.

Because the new DX coils had to fit into the existing units, exact measurements were critical. We also recommended that any replacement coils include added protection, such as:

  • Epoxy coating
  • Stainless-steel casingDX Coil
  • Copper fins
  • Other corrosion-resistant construction options

Without added protection, the farm would likely continue facing the same failures.

The Solution

The farm decided to start with one replacement DX coil as a test. Capital Coil & Air measured the original coil, built an exact replacement, and supplied the new DX coil with an epoxy coating for added corrosion protection.

The coil arrived a few weeks later and matched the original unit perfectly.

One year later, the replacement coil was still operating at full capacity with no visible damage to the finned area.

The Result

Because Capital Coil & Air was able to respond quickly, identify the true cause of failure, and recommend a longer-lasting replacement solution, the farm moved forward with ordering the remaining batch of DX coils.

That successful project also led to additional referrals throughout the local mushroom farming community. Today, Capital Coil & Air is a trusted HVAC coil replacement supplier for many of the largest mushroom farms in the United States.

When corrosive environments destroy OEM coils too quickly, Capital Coil & Air can build exact-fit replacement coils with the right materials, coatings, and construction options to extend coil life and protect critical HVAC systems.

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Coils and Counter-Flow: 5 Quick HVAC Questions Answered

In HVAC systems, understanding coils and counter-flow is critical for maintaining efficiency, preventing equipment failure, and ensuring long-term system reliability. Whether you work with chilled water coils, steam coils, DX coils, or hot water coils, correct installation and piping methods can dramatically impact performance.

Many HVAC issues begin with improper piping, poor condensate removal, and/or incorrect coil feeding. The good news? Most of these problems are completely avoidable when proper HVAC design principles are followed from the start.

This guide answers five of the most common questions about coils and counter-flow while explaining the real-world consequences of incorrect installation practices.

1. What Is Counter-Flow?

Counter-flow means air and water move in opposite directions through the coil.

  • Air: Rows 1 → 8
  • Water: Rows 8 → 1

This setup maximizes heat transfer and coil efficiency. Chilled water and DX coils are always designed for counter-flow operation.

Incorrect piping can reduce performance by 8–12%

2. Why Feed Water Coils from the Bottom?

Bottom feeding ensures all coil tubes receive even water flow.DX Cpil

Benefits:

  • Better heat transfer
  • Balanced performance
  • Prevents “short circuiting”

Top feeding can cause uneven flow and reduced efficiency.

3. What Is Water Hammer in a Steam Coil?

Water hammer occurs when steam hits trapped condensate inside the coil.

Results:

  • Loud banging noises
  • Pressure shock
  • Damaged coil joints and piping

Over time, this can lead to coil failure.

4. What Happens If Condensate Isn’t Removed?

Condensate can block steam flow and reduce heating performance.

Warning Signs:

  • One side of coil feels warm
  • Other side feels cool

Steam coils must:

  • Be pitched properly
  • Use steam traps and vacuum breakers
  • Drain condensate continuously

5. Do Steam and Hot Water Coils Need Counter-Flow?

No. Steam and hot water coils do not require counter-flow piping.Steam Coil

Key Rule:

The steam supply should enter high, while condensate exits low.

Condensate must always leave the coil properly.

Best Practices

  • Pipe chilled water coils in counter-flow
  • Feed water coils from the bottom
  • Properly drain condensate from steam coils
  • Install steam traps correctly
  • Follow manufacturer piping diagrams

If you have any questions or need assistance with installation, speak with one of our coil experts today!

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Condenser Coil Failing? Here’s Why

Did you turn on your DX system only to find the condenser coil isn’t working? It may seem like a simple fix—but it often isn’t. If you can provide the unit’s model number, there’s a good chance we’ve already built a replacement. If not, you typically face two choices: wait months and pay a huge premium through the OEM, or call Capital Coil for a faster, engineered solution tailored to your system.

Condenser Coils

Condenser coils rarely freeze, so the first step is identifying the cause of failure—corrosion, age, or vibration.Condenser Coil

Old age is the easiest to address. With a few basic dimensions—coil size, number of rows, and fins per inch—we can quickly quote a duplicate. Since condenser coils are usually outdoors, they’re easy to measure and photograph. Images of headers and return bends also help us understand circuiting and sub-cooling requirements.

Corrosion often points to poor original design. Coastal or high-salt environments can degrade aluminum fins within a year or two. To prevent this, you can upgrade to copper fins with stainless steel casings for maximum durability, or opt for protective coatings—a more cost-effective solution that typically adds just 1–2 weeks to lead time.

Vibration is another common issue, especially when coils are near moving equipment. Leaks near the tube sheet—often appearing as if the tube is being sliced—are a key indicator. Proper isolation is critical, and in some cases, oversizing tube sheet holes can help reduce stress, though not all manufacturers offer this option.

Maintenance is equally important. Because condenser coils are exposed to outdoor air, they accumulate debris quickly. With tight fin spacing (12–20 fins per inch), coils can act like filters, reducing efficiency when clogged. Regular cleaning is essential, and many customers now request thicker fins to better withstand high-pressure washing and harsh cleaning agents.

When choosing an HVAC coil manufacturer, work with a partner who guides you through the engineering process. Capital Coil & Air brings over a decade of experience, ensuring a smooth process from quote to installation. Call and speak with a coil specialist today!

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Why Are HVAC Coils Made with Copper Tubes and Aluminum Fins?

HVAC Coils

It’s no coincidence that HVAC coils predominantly use copper tubes and aluminum fins. Copper is known to have exceptional heat transfer properties, while aluminum, although effective, does not match copper’s performance. When it comes to HVAC coils, the primary goal is either cooling or heating, which means heat transfer is a top priority. Right behind that? Cost. While copper is ideal for tubes due to its efficiency, using it for fins would be economically feasible only under specific circumstances. Consequently, the majority of HVAC coils are designed with copper tubes and aluminum fins, which provide an optimal balance of effective heat transfer and cost efficiency.

Fins play a crucial role in heat transfer, accounting for approximately 65% to 70% of the total heat exchange in any coil. The tubes contribute about 30% to 35%. To achieve optimal performance, it is essential to have a strong fin-tube bond. In HVAC terminology, fins are referred to as the “secondary surface,” while tubes are the “primary surface.” Interestingly, the secondary surface—aided by the expansive fin design—carries out twice the amount of heat transfer compared to the primary surface.

In the manufacturing process, the tubes are expanded into the fins, making the fins the secondary element. Given the fin density—typically at 8 to 10 fins per inch—here is significantly more surface area from the fins than from the tubes. This further highlights the importance of a robust fin-tube bond, as it is essential for the fins to perform effectively.

Understanding the materials used in HVAC coils is critical, and the reason copper and aluminum are the materials of choice for most coils is clear. Alternative tube materials such as aluminum, 304/316 stainless steel, and 90/10 cupro-nickel can be used, but none match the efficiency and cost effectiveness of the copper-aluminum combination.

At Capital Coil & Air, we are dedicated to assisting you with all your coil selection needs and look forward to collaborating on your next project.

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Guidelines For Air Velocities

The height, length and resulting air velocities greatly figure in everything in determining the size and performance of a coil. Step # 1 in determining the size and performance of a coil is dependent upon understanding face & air velocities of air across the coil. Whether you use CCA’s coil selection program to help size the coil, or you are replacing an existing coil; the height, length and resulting velocity determine everything.

Hot Water Booster Coils

air velocities

Every coil has a specific, optimum velocity, so you want to make sure you are within 30% (+ or -) of that number. For example, booster coils have an optimum velocity of 800 ft/minute. That means that you can drop your velocity to 600 ft/minute, or conversely, increase the velocity to 1,000 ft/minute. The duct velocities are almost always higher, which means that you will need to transition to a larger coil. Try to get to as close to 800 ft/minute as possible, while sizing your coil to make the transition as easy as possible. Everything with coils is a balancing act.

Hot Water & Steam Coils

Like booster coils, hot water and steam coils should also have face velocities at approximately 800 ft./minute. Both steam & hot water coils have only sensible heating, which is why their face velocities can be the same. Face velocities ultimately control the coil’s cost, so 800 ft./minute really is a heating coil’s “sweet spot”.

If you are purchasing an air handler unit, oftentimes the heating coil is smaller than the cooling coil because the face velocities on heating coils can exceed those of cooling coils. Due to water carry-over, cooling coils cannot exceed 550 ft/minute, while heating coils only deal with sensible heat.

Chilled Water & DX Coils

Due to the limited face velocities of cooling coils, your choices are more limited. With cooling coils, your face velocity must be somewhere between 500 ft./minute-550 ft./minute. Remember that when dealing with cooling coils, you are dealing with both sensible and latent cooling, so the coil is wet. When you exceed 550 ft./minute, water carry-over occurs past the drain pans.

If you are purchasing an air handler unit, you probably will not have worry about the coil’s face velocity as most coils come pre-sized at the acceptable face velocities. Fan coils also come pre-sized with the correct CFM’s. However, if you are replacing an existing cooling coil, the face velocity must remain at or below 550 ft/minute!!

 Air Stratification Across The Coil

Air does not travel equally across the face of a coil. If you were to divide a coil into (9) equal sections, like a tic-tac-toe board, you would see a high percentage of air travelling through the center square, rather than the corner squares. In a perfect air flow scheme, 11% of the air would travel through each of the 9 squares, but that is not what happens. Because more air travels through the center of the coil, you want to avoid putting a fan too near the coil. Due to central air flows, most systems are draw-thru, rather than blow-thru. This is also why you want to avoid installing your coil near any 90 degree angles/turns in the ductwork. Avoid any situations that contribute more than the “natural” air stratification to help ensure your coil is at maximum efficiency.

In some situations involving cooling coils, you will have water carry-over even when the coil is sized correctly. How can this happen? Think about the tic-tac-toe board again. Air velocities are exceeding 700 ft./minute in the coil’s center, while the corners are around 300 ft./minute. This cannot and will not work.

Coils do not have any moving parts. They simply react to the air across the outside of the coil and whatever is running through the inside of the coil. Coils are 100% a function of your entire system, as well as the installation in general.

Capital Coil & Air is here to help with any coil selections that will help avoid costly missteps that lead to wasted time and money. Call us on your next project, we greatly look forward to working with you!

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Why Cooling Coils Need to Be Replaced

In theory, properly engineered and maintained cooling coils should deliver 20+ years of service life. In practice, most coils are replaced prematurely. The root causes are typically operational neglect, environmental exposure, improper application, or design limitations. Below are the three primary drivers of early replacement, along with technical context.

1. Increased Air Resistance from Coil Plugging

Cooling Coils

Failure Mechanism:

Airborne contaminants (dust, pollen, fibers, grease aerosols) penetrate beyond the fin surface and embed deep within the coil core. Once lodged between fins and tubes, they cannot be fully removed by routine air-side cleaning.

Primary Causes:

  • Poor filtration

  • Irregular filter replacement

  • Lack of annual coil cleaning

  • High-particulate environments

Performance Impact:

  • Increased air-side static pressure

  • Reduced airflow (CFM)

  • Decreased heat transfer 

  • Reduced system capacity and efficiency

Plugged cooling coils often force the fan to operate outside design conditions, increasing energy consumption while lowering cooling output.

2. Freeze Damage

https://www.resideo.com/us/en/-/media/Resideo/Corporate/Media%20Images/Featured%20Articles/120121/cracked-pipe_850.jpg?h=567&hash=607EE03C7CC57A4AC0E0DCCC6025A398&rv=9d8b4e00150d48e49dbc73a3291c6451&w=850
 

Failure Mechanism:

Water trapped in coil tubes expands during freezing, generating internal pressures sufficient to rupture copper tubes.

Why It Happens (Even When Dormant in Winter):

  • Circuiting designs that prevent full drainage

  • Drain connections positioned above low tubes

  • Lack of glycol protection

    broken return bends

  • Inadequate winterization procedures

Consequences:

  • Multiple hidden leaks

  • Thinned tube walls due to pressure expansion

  • Progressive failures after initial repair

  • High risk of recurring leaks

Once a coil experiences extensive freeze damage, repair becomes unreliable. The metallurgical integrity of the tubes is compromised, making replacement the only durable solution.

3. Corrosion

https://static.wixstatic.com/media/ea3647_d85a052e6f8a4b5ab1c1d0555c623a28~mv2.jpg/v1/fill/w_1000%2Ch_750%2Cal_c%2Cq_85%2Cusm_0.66_1.00_0.01/ea3647_d85a052e6f8a4b5ab1c1d0555c623a28~mv2.jpg
Corrosion occurs on both the air side and the fluid side, often simultaneously.

Air-Side Corrosion

  • Salt-laden atmospheres (coastal or industrial)

  • Hydrogen sulfides (e.g., wastewater treatment facilities)

  • Chemical exposure in manufacturing environments

Visual Indicator:

A white ring around the tube-to-fin interface. This indicates loss of mechanical bond and reduced thermal conductivity between tube and fin.

Effects:

  • Reduced heat transfer

  • Loss of tube/fin contact

  • Core blockage from corrosion byproducts

  • Elevated air pressure drop

Water/Refrigerant-Side Corrosion

  • Raw, untreated water

  • High mineral content

  • Improper water chemistry control

Internal corrosion weakens tube walls and leads to pinhole leaks, particularly in copper tubing exposed to aggressive water conditions.

 

Key Takeaway

Cooling coil replacement is common—but preventable. Most failures are not random; they are the result of design limitations, environmental exposure, or maintenance gaps. Replacing a coil without diagnosing the root cause often guarantees another premature failure.

If longevity, efficiency, and reliability matter, the solution isn’t just replacement—it’s engineered improvement.

 

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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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Chilled Water Coils – Circuiting Made Easy

Chilled Water Coil

Circuiting chilled water coils is one of life’s great challenges in the coil business. You’re bound to run across folks with years of experience in the industry that can not effectively explain this concept. While not the most exciting of subjects, the necessity of circuiting chilled water coils can not be overstated. Capital Coil & Air has attempted to simplify the idea of circuiting as much as possible.

For starters, circuiting chilled water coils is ultimately up to the performance of those coils. Circuiting is really a balancing act of tube velocity and pressure drop. In other words, think of a coil as a matrix. Each coil has a specific number of rows, and a specific number of tubes within each row. For example, a chilled water coil might be 36 inch fin height and 8 rows deep. The coil has 24 tubes in each row, and multiplied by 8 rows, there is a total of 192 tubes within the coil. While you can try to feed any number of tubes, there are only a few combinations that will work.

    • Feeding 1 tube – you will be making 192 passes through the coil, which will essentially require a pump the size of your car to make that process work.
    • Feeding 2 tubes – equates to 96 passes, and your pressure drop will still be enormous.
    • Feeding 3 tubes – 64 passes, which is still too many.
    • Feeding 4 tubes – See above.
    • Feeding 5 tubes – Impossible as 5 does not divide evenly into 192 (passes).
    • Feeding 6 tubes – Still constitutes far too many passes, which again leads to additional pressure drop.
    • Feeding 7 tubes – Same rule for feeding 5 tubes.
    • Feeding 8 tubes –  Same rule for feeding 6 tubes.
    • Feeding 24 tubes – This feed consists of 8 passes, which is in the ballpark, and with a pressure drop you can live with.
    • Feeding 32 tubes – 32 tubes will see 6 passes. You might see a slight decrease in performance, but it’s off-set by a continuously better pressure drop.
    • Feeding 48 tubes – The magic combination, as 4 passes typically elicits the best performance and pressure drop simultaneously.

 

Rule #1: The number of tubes that you feed must divide evenly into the number of tubes in the chilled water coil.

Rule #2: The chilled water coil must give you an even number of passes so that the connections end up on the same end.

Rule #3: Based on the number of passes, you must be able to live with the resulting pressure drop. Acceptable tube velocity with water is between 2 and 6 ft. per second.

You’re bound to run into different terminologies depending on the manufacturer. More times than not, the different verbiage confuses more than it clarifies. However, understanding the basic tenets of chilled water coil circuiting will remove much of the perceived difficulty.  

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Top 10 Fan Coil FAQ’s

1. A fan coil is among the easiest units to understand in the HVAC industry.  Basically, there is a small forward curved fan, a coil, and sometimes a filter.  They are all direct drive units. Click HERE to see Capital Coil’s full Fan Coil Product Lineup.

2.  Fan coils run from 200 CFM to 2200 CFM, which is 0.5 ton through 5.5 tons.  Anything larger than these sizes requires a belt drive unit…which is really a full fledged air handler.

3.  The thing that differentiates fan coil units is where and how they are going to be installed.  Is the unit going to be hidden above the ceiling or maybe in a closet?  Or is it going to be exposed so that everyone can see it?  Will it be ducted or will it just pull air from the space where it’s located?  These are things that determine the configuration of the unit and which style of unit to choose.  But, every unit has 3 things in common:  fan, coil, and sometimes a filter.

Fan Coil 4.  Some units have (2) coils.  One for heating and one for cooling.  Obviously, there is a separate supply and return connection for each coil and these units are known as 4 pipe fan coils.  Many units only use the same coil for both heating and cooling and these units are 2 pipe fan coils.

5.  Units are either horizontal or vertical depending on the orientation and flow of the air.  A typical fan coil in a hotel room is a vertical unit with a mixture of air coming from outside and the air recirculating in the room.  The air enters at the bottom of the unit and is drawn upward through the fan.  This makes the unit a vertical style.  Many units are horizontal with the air entering at the back of the unit and traveling horizontally through the unit.

6.  Almost all fan coils are 3 speed or infinite speed settings based on the controls.  The high speed gives you more BTU’s, but more noise too.  Because the unit is direct drive, when you dial down the speed, you also dial down the performance.

7.  Coils in the units tend to be 3 or 4 row deep coils.  3 row is typically used the most, but if you need the extra performance, 4 row is the way to go.  Performance is always governed by the cooling aspect.

8.  Fan coils sometimes have short runs of duct work and there is static pressure on the unit.  Static pressure reduces the amount of CFM and BTU’s that the fan coil can give you.  This is true of both horizontal and vertical units.  Most performances listed on charts that you will see are static free performances.

9.  The control systems for fan coils are often more complicated and more expensive than the units themselves.  There are balancing valves, isolation valves, unions, y-strainers, p/t plugs, air vents, ball valves, thermostats, condensate float switches, and disconnects.  Capital Coil & Air can do this at the plant, but it is much cheaper and easier to do it at the installation. 

10.  Just describe your installation requirements to a sales engineer at Capital Coil & Air and they will guide you to the right design and configuration of the unit for you.  It requires only a phone call or e-mail! We look forward to working 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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