Why Your AC Is Freezing: 3 Common Reasons

AC freezing up? How can something that works all day during the hottest days of the year be prone to freezing? Despite the irony of an AC freeze in the summertime, an air conditioner freeze up is fairly common. Not many homeowners are equipped with the knowledge and understanding about air conditioners to prevent this problem on their own. It’s a problem that can turn a beautiful summer day into a blistering hot one in minutes.

How can you tell if you might be facing a freezing problem?

A sure sign is to check the supply registers. Is it blowing warm? If so, that is usually a good indicator of frozen evaporator coils. Open the panel and check for ice. Keep in mind, a lack of ice doesn’t necessarily mean that you’re not having a freezing problem. If you see ice…it’s frozen.

Understanding the Joule-Thomson effect

Before we delve into the causes of an AC freezing up, let’s talk a little bit about how your AC works. First, we must understand that temperature is how much energy a molecule has. When the air feels hot, it’s because the molecules in the air have a lot of energy and are moving around rapidly. The same works in reverse, cold air is comprised of low energy molecules. So, what the Joule-Thomson Effect demonstrates in thermodynamics is when the air in our ACs isn’t compressed, its temperature will decrease as it expands and the molecules slow. When it is compressed, the molecules get excited and heat up.

The point of an air conditioner is to expand the refrigerant inside the evaporator coil so that it cools down, so when it leaves the air conditioner, it cools the air inside your home and effectively removes the hot air from inside the house. However, if something in the air conditioner malfunctions, the whole system gets disrupted. This causes the evaporator coil to allow the refrigerant to cool too much, causing it to fall below freezing and ice over.

So, how can you prevent something in the cooling equation from going terribly wrong? There are three main causes that lead to an AC freeze up. By understanding these causes, you can get out in front of them so you never have to experience an AC freeze. However, if you’re reading this too little too late, we’ve included some solutions!

Blocked Air Flow Causes Freezing Up

This is arguably the most common cause that we see. Air conditioners need to have a constant flow of air so that humidity can’t settle on the coils and freeze. In order to keep the air flow in your own house moving enough to not disrupt your air conditioner’s functionality, you need to be sure your air filters aren’t dirty and becoming clogged. This restricts the air flow in your house.  Keeping your AC clean and tuned up is also a good idea for preventing air flow problems, and other problems in general.

How to Fix It:

Your AC is already blocked, and you discovered that your air filters were clogged. It’s likely a blocked air flow problem. The first thing you need to do is turn off the air conditioner and let it defrost. After it’s had sufficient time to thaw (usually overnight), turn on just the fan for about an hour. Use this time to change your air filter. You can check out our article on when to change your AC filters. After that, your AC should be back to normal working order.

Mechanical Problems or Refrigerant Leaks?

Air conditioners are full of moving parts that can get stuck, broken, or clogged. Refrigerant lines can kink, fans can stop moving, filters can become clogged, and things can leak. Any of these things causes a drop in pressure, allowing the refrigerant to expand too much and become too cold. Refrigerant is also an essential part in ensuring a regulated temperature throughout your machine. A too-low level of refrigerant is also known to cause freezing up. Some of these problems are easier and cheaper to fix than others. In the case of a coolant leak, any fix is likely to just be a temporary fix. Especially in older R-22 charged systems. It may be time to consider investing in a new machine.

How to Fix It:

Mechanical problems and leak repairs go a bit beyond a short guide to AC freezing. It’s best to tackle these problems with the help of Spurk HVAC. Our expert technicians know how to handle refrigerants and keep them contained. If you suspect mechanical failure or leaks might be the cause of a malfunctioning AC, contact us so we can come give the problem a look. You can help prevent catastrophic issues with your AC by getting regular tune-ups with a planned maintenance agreement.

Cool Nights Can Cause Your AC to Freeze

Air conditioners are calibrated to operate within a certain set of optimum temperature thresholds. When nights in the summer time are colder than the optimum threshold can account for, it can throw an AC out of whack.

How to Fix It:

Having a programmable thermostat can automatically get ahead of the problem by shutting down the AC when temperatures get below 60 degrees. If you don’t have a programmable thermostat, keep an eye out on the current temperatures each night and anticipate if it’s going to be colder than 60 degrees. In which case, you should turn off your AC and open your windows to let in the breeze instead.

Summing It Up

A freezing AC is a very common, frustrating problem that homeowners face. However, the problems causing a frozen AC are preventable with some regular maintenance and tune-ups. Tune-ups and changing air filters regularly go a long way to preventing mechanical failures, clogs, and leakages. Hiring Spurk HVAC and taking advantage of a planned maintenance agreement, will help you keep your AC in tip-top shape,  will save you money on your energy bill and help keep your AC unit running for years and years.