Why Is My Air Conditioner’s Refrigerant Line Covered in Ice? Your outside air conditioning refrigerant line is covered in ice—which seems crazy in Arizona heat. Chances are, the indoor unit’s evaporator coil is frozen solid and cold liquid refrigerant is flowing to the outside unit through the refrigerant line (which is why it’s covered in ice). This is an evaporator coil. DO THIS RIGHT NOW: Turn off your AC and turn the fan setting to “On.” This will unfreeze the evaporator coil and prevent any damage to the compressor (a very expensive part you don’t want to replace). Now, let’s delve into what can cause an evaporator coil to freeze up and what you can do to ensure this never happens again. What causes the evaporator coil to freeze up An evaporator coil, a group of copper tubes, freezes when the refrigerant flowing through the tubes gets too cold, causing the moisture in the surrounding air to freeze. So what causes the refrigerant to get too cold?

Usually, it’s one of two things: Low airflow over the evaporator coil Low amounts of refrigerant What can cause these two problems? Let’s divide the possible causes into things you can solve right away and things you’ll need a technician to solve.clean home ac unit Problems you can fixis there a tax credit for ac units Clogged/dirty air filter—A dirty filter reduces airflow over the evaporator coil, causing it to freeze. ac units used in hotelsCheck the filter at least once a month. Closed supply vents—Don’t close supply vents (the vents that blow air out)—even in unused rooms. Closing vents reduces airflow over the evaporator coil. Blocked return vents—Ensure that furniture or curtains aren’t blocking the return vents (the grates where air gets sucked in).  

Like closing supply vents, this reduces airflow over the evaporator coil. Problems a technician needs to fix Refrigerant leak— The main cause of low refrigerant is a refrigerant leak. The technician needs to evacuate the remaining refrigerant, and then find and—if possible—fix the leak. Malfunctioning indoor blower— If the blower isn’t working properly, there may not be enough air blowing over the evaporator coil, causing it to freeze up. Dirty evaporator coil—Dirt blocks airflow over the evaporator coil, causing it to freeze up. Note: This list isn't exhaustive; it’s just a quick overview of common problems. Change the filter, and open and unblock any supply and return vents. If your evaporator coil (and refrigerant line) starts to freeze up again after doing these tasks, then you need a technician’s help.There is ice on my AC unit. May 26, 2012   Subscribe So my air conditioning is not blowing cold air. I go to the basement to check the unit, and there is about a half-inch of ice on the main pipe leading out of the unit.

Figuring out what is causing your air conditioner to ice up can be frustrating, but it is not an uncommon problem.  If you’ve read any of our articles, then you know that we are a small, U.S. Veteran-Owned company in Southern California, and pride ourselves on giving honest, straight answers.  In fact, most of our posts address either one of two things: first, common air conditioning problems that people have; or second, the questions we get asked most frequently.  We are often asked the question, why is my air conditioner freezing up?  There are a number of reasons for an air conditioner to freeze up, and it really doesn’t matter whether it is a window AC unit or a central air conditioner – the causes of, and solutions to, an air conditioner that keeps freezing up are exactly the same.  It is important to address this issue – a frozen air conditioner will not only cool improperly, but can actually be severely damaged if it keeps freezing up.  If you have this problem, you have to address it immediately – it won’t solve itself.  

In this article, we will tell you what causes a central air conditioner to freeze up, and what you can do to fix it. Standby for a small high school physics lesson.  We don’t need to go too in depth, so bear with me, but understanding this principle is the key to figuring out why your air conditioner is freezing up.  The Joule-Thomson Effect is a principle in thermodynamics which states that if everything else is kept constant, then as a gas expands, its pressure decreases, and its temperature will also decrease.  Likewise, as a gas is compressed, its temperature will increase. This is because what we sense as temperature is really just a measurement of the amount of energy a molecule has.  Simply put, if air molecules are bouncing around rapidly, then you would feel this air as hot.  If air molecules are moving around slowly and sluggishly, then you would feel this air as cold.  This is important to understand because it forms the basis for how your air conditioner works.  

Your system works by allowing your evaporator coil to expand refrigerant inside of it, causing the coil to cool rapidly.  As this rapidly cooled coil comes into contact with your home’s air (which your air conditioner blows over this now cooled coil), the refrigerant absorbs the heat from the air inside of your home. This newly heated refrigerant is then transported outside of your home where it is compressed, causing it to heat up and transfer the heat that was once inside of your home to the outside air.  The cycle then repeats itself over and over again, cooling your home in the process.  For more information on the Joule-Thomson Effect, visit this page on Wiki: Joule-Thomson Effect. Why is this important?  Well because this effect is used to allow your air conditioner to cool the air inside of your house.  But any time you change part of the equation, you might throw the system out of whack.  So to keep this simple, your air conditioner is freezing up because something has altered your system in such a way that it is cooling your evaporator coil more than it should, causing the unit to freeze up.  

Now that you know how, what you have to do is figure out why your air conditioner is freezing up, and to do this you have to figure out what it was that threw your AC system out of whack.  We will do this in the next section. If you want to delve more into how exactly it is that your air conditioner cools air, take a look at: The Joule-Thomson Effect – Why Your Air Conditioner is Freezing Up, or just watch the video below: Now that you have a basic idea of how your air conditioner uses expansion and compression to heat and cool its Freon (what is Freon?), you can figure out why your central air conditioner is icing up. Your air conditioner can freeze up for a variety of reasons, so we will discuss them from the most common to some of the more rare causes of ice up.  All of these causes are rooted in the Joule-Thomson Effect discussed above, so if you skipped past it, I’d recommend that you take a quick look or just watch the video above.  Simply put, your air conditioner is freezing up because something is either causing the Freon in your system to expand more than it is designed to, which in turn is making your coils colder than normal, or something is preventing the air in your house from transferring its heat into your system.  

Either way, this causes your evaporator coil to drop below freezing and your air conditioner to freeze up.  Here are some common causes: But which is it and how do I fix it?  How to troubleshoot an air conditioner that is freezing up will be discussed in the next section: Just because your air conditioner is freezing up does not mean that you have to call your HVAC contractor!  Some contractors will tell you that they are the only ones that should touch your AC unit (I have never believed that), and if you don’t feel comfortable around your air conditioner then you should definitely call out a contractor.  Either way, the first thing you need to do is turn your air conditioner off and allow it to defrost.  Ice can harm your air conditioner!  Next, if you do feel comfortable and if you have even a basic touch of the handy-man bug, then there are a few things that you should take a look at before you call your local air conditioning repair service.  In order to troubleshoot a frozen air conditioner, I’d recommend you do the following steps in order:

I would start by ensuring that you never run your air conditioner when the temperature is below 62 degrees outside.  If you are, then stop it and see if this fixes the problem.  This is the simplest thing to fix but can cause big problems.  Next, if your air conditioner is freezing up from restricted air flow, then you need to rule this out – the best way to rule this out is by checking the following: If your air conditioner is still freezing up after the above steps have been taken, then I’m afraid you’ve done all that you can in the do-it-yourself category.  Call out an HVAC contractor.  The next likely causes are a low pressure system due to low refrigerant levels, or too much refrigerant, which can only be recharged by a licensed HVAC technician (at least where we are in Santa Clarita), or it is also possible that you have a problem with your blower fan or refrigerant lines; neither of which you will want to mess with yourself.  At this point, I would give your local HVAC contractor a call (and if it is time to buy a new air conditioner, make sure that you take a look at this article first: The Best Time of Year to Buy an Air Conditioner.  

It is unlikely that everyone who is reading this is in All Systems Mechanical’s service area of Santa Clarita or Greater Los Angeles, so I’ve included an article to help you choose a reputable air conditioning contractor in your local area: How to Choose a Contractor. We often get asked the question, “why is my air conditioner freezing up?”  Hopefully this article has answered your question and provided you with some useful information about what can cause your air conditioner to freeze up, as well as how you can fix it.  A frozen air conditioner not only does’t work properly, but it can damage your unit.  Think about what ice does to roads over time – it expands and damages them.  It splits them up, and can do the same thing to your air conditioner.  This won’t fix itself, so turn it off, follow the above steps, and you will have a healthy air conditioner that runs for years to come.  For more information on frozen air conditioners, and other air conditioning problems that you can troubleshoot yourself, visit the ASM Air Conditioning Blog.