What Does “Splitting” DX (Evaporator) Coils Mean

***Now Offering R-454B Refrigerant for All DX Coils

“Splitting” DX (Evaporator) coils is one of the toughest concepts to understand in the coil business. “Splitting” the coil simply means that (2) or more compressors can operate off of the same coil. One obvious advantage, or reason that you might “split” DX (Evaporator) coils is that you can shut down (1) of the compressors when the cooling load does not require it. This in turn saves energy, which saves $ when the cooling load is not operating at maximum design conditions. For example, let’s use a coil that is designed to give you (40) tons, but the coil is split so that (2) 20-ton compressors are feeding the same coil. If you only require ½ of the maximum load on any given day, you can shut down (1) compressor completely and operate the other one at 100%. This is a money-saving feature that you need to be aware of if you deal with DX coils on a regular basis. This requires special circuiting arrangements, and this is where the confusion starts with most folks. There are three primary ways to deal with this:DX (Evaporator) Coils

FACE SPLIT

Splitting the coil is nothing more than putting (2) completely separate fin/tube packs (coils) into one common casing. When you hear the term “face-splitting” a coil, you are drawing a horizontal line from left to right across the face of the coil and dividing the coil into a top and bottom half. It is like having two separate coils in one casing in that each half is circuited by itself. You hook up (1) compressor for the top half, and (1) compressor for the bottom.

In practice, this configuration is no longer used with much frequency because this arrangement leads to air being directed across the entire face of the coil. This disadvantage is especially apparent when only one half of the coil is in use because you’ll need a complicated damper/duct system to ensure that air is only directed to that portion of the coil in operation.

Row Split

“Row splitting” a coil is dividing the coil by drawing a line vertically and putting some portion of the total rows in (1) circuit, while putting the remaining rows in the other circuit. With this configuration, the air passes across the entire face of the coil, and will always pass across the rows that are in operation.

Please be aware that this configuration also comes with certain issues in that this kind of split makes it very hard to achieve a true 50/50 split. Let’s use an (8) row coil as an example. You would like to “row split” this coil with (4) rows/circuit, which would appear to be a perfect 50/50 split. The problem here is that the first (4) rows, located closest to the entering air, pick up a much higher portion of the load than the last (4) rows. In actuality, this coil’s split is closer to 66% / 34%, which will not match the 50/50 compressors. Another option is try to split the coil between (3) & (5) rows. While not 50/50 either, this configuration is closer. However, a new challenge arises because you have now created a coil that is very difficult to build and correctly circuit. In short, you need almost perfect conditions along with a degree of luck to achieve a true 50/50 split using this method.

Intertwined Circuiting

The most common to split coils today is to “intertwine” the circuiting. This means that every alternate tube in the coil is included in (1) circuit, while the other tubes are included in the (2nd) circuit. For example, tubes 1, 3,5,7,9, etc. in the first row are combined with tubes 2, 4, 6,8,10, etc. in the second row. The same tubes in succeeding rows form (1) circuit. You are essentially including every alternate tube in the entire coil into (1) circuit, which (1) compressor will operate. All of the remaining tubes not included in the first circuit will now encompass the second circuit.

The advantage of this configuration is that the air passes across the entire face of the coil, and, if one of the compressors is on, there are always tubes in operation. Every split is now exactly 50/50 because it cannot be any other way. Most DX coils are now configured in this manner due to these advantages.

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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Now Offering R-454B Refrigerant for All DX Coils

In keeping with most of the OEM’s in 2024, 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 of 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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Steam Distributing Coils (Non-Freeze)

Steam Distributing CoilsWere you aware that Steam Distributing coils or “Non-Freeze” steam coils were essentially discovered by accident? First, it must be mentioned that there is no such thing as a 100% “Non-Freeze” steam coil because under the right conditions, any coil can freeze. As such, Capital Coil tries to steer clear of the term “Non-Freeze” because it is a mischaracterization. Steam Distributing Coils is the correct terminology that Capital Coil uses when speaking about steam coils that see entering air temperatures under 32* F. Trapped condensate in the tubes and/or headers, coupled with entering air temperatures below 32*F over the face of the coil, creates a situation with a near-100% certainty that your steam coil will freeze. Because of this, there is no magical solution to fully eliminate freezing your coil, which again is why Capital Coil does not use the term “Non-Freeze”.

Steam turns to condensate little by little as it travels through the coil. Lower pressure steam turns to condensate faster than higher pressure steam!! The longer the tube length in the coil, the earlier the condensate is formed, and the longer it has to travel through the tubes. One very important fact to always remember is that too much condensate in a steam coil IS NEVER A GOOD THING…under any circumstances! Because of this requirement, everything is designed to ensure the removal of all condensate from the coil. Systems are heavily designed with float & thermostatic traps, vacuum breakers, and placement of piping to help get rid of any remaining condensate.

Another headache that occurs when condensate freezes is that it creates a “water-hammer”. A “water-hammer” can best be described as a loud banging noise as the steam is coming into contact with the condensate in the coil. It does not allow the steam to be evenly distributed across the face of the coil…again not a good thing!

At the inception of the HVAC industry, steam coils were originally designed to be shorter in length because there was not a good way to evacuate condensate. In an effort to make steam coils longer in length, the concept of a steam coil containing a tube within a tube was invented. The steam feeds only the inner tubes, which travels the entire of the length of the outer-tube. Holes are placed every 12” with the inner tube releasing condensate to the outer-tube. The idea is that the condensate is slowly and evenly “distributed” across the entire length of the coil. Heating is also evenly applied across the coil’s face, and if the casing is pitched at a downward angle, condensate cannot remain trapped. It was later discovered as an added bonus that under most circumstances these coils will not freeze. So while the concept was never designed or intended to become known as “Non-Freeze”, they are now used in almost all projects dealing with air temperatures below 32*F. Please keep in mind that you will still need all of the other steam protective devices in the system, including the freeze-stat, but all in all, it is much more difficult to freeze coils today than it was 30-40 years ago. Necessity may be “the mother of invention” but this great concept was discovered accidently.

Capital Coil is available for all of your coil-related trivia needs, so please don’t hesitate to reach out whenever we can be of assistance.

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