Tips on Hand Designation & “Counter-flow”

Are your chilled water coils right hand vs. left hand?  Is it looking into the face of the coil or with the air hitting you in the back of the head?  What exactly is counter-flow and why is it important?  Are you completely confused by why right hand vs. left hand even exists?  Most manufacturers probably do not know or understand the technical reasons themselves. 

First, let’s figure out what coils even need a hand determination.  Chilled Water Coils, Direct Expansion (Evaporator) Coils, and Condenser Coils are the only coils that need this figured on almost every job.  Hot Water Coils, Booster Coils, and Steam Coils rarely need this determination.  The reason for this is when the coils are only 1 or 2 rows deep, they can be flipped over.  When a chilled water coil is 3+ rows deep, hand determination is much more important because it needs to be counter-flow.  Most suppliers determine hand designation with the air hitting you in the back of the head….do you want the connections on the right or left? 

Chilled Water CoilsYou’ve probably heard the term “counter-flow” countless times, but here’s the simplest explanation.  For peak performance, you want the air and the fluid traveling in opposite directions through the coil.  Is it the end of the world if your coils are not counter-flow?  The short answer is no, but you will lose anywhere from 12-15% of the output.  So if your coils are piped incorrectly, don’t expect to get the full performance.  Steam and hot water coils are 1 or 2 rows deep, so counter-flow is pretty much irrelevant.  However, it can make a big difference with any chilled water or direct expansion coils (3-12) rows deep.

We also get asked many times “what is the proper way to pipe coils?”  Put simply, steam coils should always be fed on the highest connection and the return on the lowest connection.  Water coils should always be fed on the lowest connection and returned on the top connection. 

Hand designation and counter-flow are two pretty simple concepts when they are properly explained.  When dealing with a 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 in handling pretty much any scenario that you may come across, so we want to be your coil resource for any and all projects. Please give us a try on your next job!

RELATED POSTS

Why are HVAC Coils Copper Tube and Aluminum Fin?

Did You Know? Facts about Commercial HVAC Coils

You should never have to worry about performance on replacement coils…Well, almost never!

 


10 Things You Need to Know to Buy Replacement Coils Effectively

Replacement Coils

 1.  Are you replacing an existing coil or are you installing a coil for a new application?  This is always the first question you will be asked.  If you are replacing an existing coil, matching up the dimensions of the coil is your first responsibility and matching up performance is easy.  It just happens.

2.  The laws of physics apply to coils like everything else. If you match up the physical size of the coil, the rows deep and the fins/inch, you will match or exceed the performance at a minimum.

3.  If you don’t know the performance, then based on the physical size of the coil, you can ask somebody to run you a typical performance.  There are standard air velocities, standard fluid temperatures and other performance requirements that dictate what a typical performance could be.  Of course all of this is based on the idea that you are talking to a supplier that knows what he/she is doing and can walk you through this.

4.  Coils fail primarily for four reasons.  The first is old age.  The second is that the coil failed prematurely and you must discover the reason it failed…or you’ll just duplicate the problem.  The third is the coil froze in some manner.  The fourth is that the coil never worked properly from the beginning of the installation.  Your replacement coil has to fit in one of these four categories.

5.  If a coil dies of old age, then consider the application to be a lucky one and duplicate the coil.  “Old age” can be defined as roughly 15 years or more. Duplicate the coil as exact as possible, slide the old coil out, and slide the new coil in.

6.  Coils can fail prematurely for a variety of reasons.  It could be corrosion or erosion.  Maybe the system is not set up correctly for the coil.  But, if the coil fails in 2 or 3 years, you need to be asking yourself some of these questions about the coil and the system.  And something needs to change so you don’t duplicate the problem!

7.  Coils freeze and that’s a fact of life.  Coils do not freeze mysteriously by themselves.  They are not independent of the system.  Something in the system needs to be corrected.  A good replacement coil supplier will work with you and give you lots of engineering recommendations and suggestions.

8.  If the coil never worked correctly from the beginning, then change it.  It’s very easy to determine where you are and where you need to be in terms of coil performance.  Again, it takes a replacement coil supplier who is willing to work with you instead of berating you for asking questions.

9.  You never get something for free when you buy a replacement coil.  Coils can become more economical if you increase the fins/inch and decrease the rows.  But it’s a trade off because you also increase the air pressure drop and cleaning the coil becomes much more difficult when the increased fins/inch acts like a filter.  There are all kinds of shortcuts that you can take to build a coil that will save you money.  None of them lead to a good coil selection and low energy costs.  The saying “you get what you pay for” is never truer than in buying coils.  There is always a “balance”.  You need to find it with your replacement coil supplier.

10.  There is an urgency to any replacement coil installation.  There is an urgency to designing the replacement coil properly.  There is an urgency to getting an competitive price.  There is an urgency to getting the approval drawings.  There is an urgency to shipping the replacement coil out on time.  There is an urgency to delivering the coil.  You must work with a supplier that can recognize you situation individually and provide you with the service that you require.  At Capital Coil & Air, we’re the best in the industry in all of the above.  We look forward to working with you on future projects!

RELATED POSTS

Top 5 Reasons HVAC Coils Prematurely Fail

Repair or Replacement Coils?

Coil Costs: What Will Make Your HVAC Coils More Expensive?


Replacing HVAC Coils? 10 Common Ordering Mistakes

For those of you that do not regularly deal with replacement HVAC coils, here are some of the more common mistakes made that you want to avoid: 

  • When attempting to cross-reference a coil replacement within an Air Handling Unit, avoid using the Air Handling model number. You always want to use the coil’s model number because an Air Handling Unit might contain numerous coils with varying dimensions. 
  • Never go “big” on a dimension. Always error on the smaller side because even if smaller than intended, the coil is still useable. If you’re too big, your coil is essentially useless.
  • Avoid packing more Fins per Inch to try to get more performance out of the coil. Coils with added and packed Fins per Inch are extremely hard to clean, and the harder to clean, the less performance the coil generates.
  • Do not get hung up on small differences in performance. Coils are not tested with small tolerances, so generally, if you are within 3% (+ or -), everything will function as planned.
  • If you find that you have a corrosion issue, do not try to be economical. You will just end up replacing the same coil again within a year or two. Within the total context of a job, coil coatings and/or stainless steel casings are not too expensive. Do yourself the favor and spend the extra money upfront to make sure the problem is corrected sooner rather than later.
  • Stay away from running computer-generated performance without someone at Capital Coil running it as well. Coil selection programs have features and options that may not be relevant to your project, so we’ll help you to steer clear of those selections. We obviously want to make sure our results match up with yours, so working alongside each other helps ensure that.
  • Please do not try to “tweak” the program to increase one specific area. No matter what, there is always a cost and a counter-balance. The costs come in the form of pressure drops, additional rows, more Fins per Inch, etc. The central idea is to balance everything so that you have a selection that you can ultimately live with.
  • Do not think that connection locations can be matched up to ¼”, (+ or -). All coils require small offsets in the piping to accommodate new coils.
  • Steam coils only work well when the system and installation are correct. As such, do not install any steam coil without knowing everything about the system, valves, and controls around it.
  • Do not rely on just proposals and quotes to order your coil. Capital Coil & Air will always send over drawings for your records. Please look hard at these drawings for any revisions to be made prior to production. It’s all of our responsibility to make sure these projects are done correctly and on-time.

When dealing with a 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!

RELATED POSTS

Coil Costs: What Will Make Your HVAC Coils More Expensive?

Are You Asking Your Coil Supplier These Questions?

Top 10 Chilled Water Coil Facts