Case Study: We Need These Coils on a (5) Day Quick-ship

In late June, Capital Coil received a call from a Trane office in Ohio regarding quick-ship availability. One of Trane’s top customers had an urgent need for (12) large chilled water coils with stainless steel casing. The problem/hurdle that they were encountering was that they needed all (12) coils to be built and ship out of the factory in (5) business days. Completion of the whole project was 100% contingent on them receiving the coils in their specified time-frame. An additional complication was the fact that July 4th was the following week, and they needed to have the coils ship prior to the holiday.

Trane shopped the project around to different manufacturers, but not one could guarantee to ship in (5) days. Some manufacturers waffled and claimed that they could have them built in (6) or (7) days, but not one could guarantee to ship in (5) days. A sales rep in that same Trane office, who had worked with Capital Coil previously, suggested that his co-worker reach out to us to see what we could do. After speaking with Trane’s project manager, we immediately contacted our head of production to make sure that we had the capacity to complete all (12) coils in the required (5) days. She assured us that we had the materials and manpower on-hand to get them all built and ship on time. We agreed to accept the project and began work on the coils immediately.

Due to the size of the project, as well as it’s time-sensitivity, we had multiple calls daily with our factory to ensure that everything was proceeding on schedule. We then gave Trane daily status updates, so they were constantly informed of everything from the brazing of the coils to entering the final testing phase. Chilled Water Coil

As promised, all (12) coils were built correctly and shipped out in the required (5) days. Our logistics team was then in constant communication with the freight company to make sure that the delivery was on schedule. And just like during the production phase, we passed daily tracking updates along to Trane, so they knew where their coils were at all times and when they could expect delivery. All (12) chilled water coils arrived on July 3rd with zero freight damage, and the project was completed on time!

A company as large and influential as Trane can have their coils built by anyone, but Capital Coil was the only manufacturer that could guarantee to have their coils built and shipped by a required date. Additionally, in working so closely with Trane throughout the whole process, they were kept up-to-date in real time from the start of production to final delivery.

Capital Coil offers a level of service that you won’t get with other manufacturers. When we guarantee to ship by a certain date, we stand by that guarantee, or you do not pay!

 

Trane’s project manager’s comments to Capital Coil upon completion/delivery:

“This will help us get a jump on this project prior to the big event taking place next week! 

I will make sure to share your information with others across our great lakes region about our experience with your company, so that they know we have THIS option to go to for our coil needs. THANK YOU ALL!!”

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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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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